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Gas: Is Higher Octane Worth The Cost? - The Definitive Answer... I Think

 

Hello, All! So I thought I'd do a little test and share my results with you as I'm sure most of you drive when you take trips with your GPS. With the continually increasing cost of gas these days and with everyone wanting to get the most out of their dollars, I wanted to figure out if paying for a higher octane gas was really worth the increased cost at the pump for any gains in fuel economy.

First, a little background. I do a lot of driving in my job, averaging around 5,500 KM's (3,400 Miles) per month. I figure about 85% highway and 15% city driving. Average driving speed is about 80 KM/H (50 MPH) and overall speed is around 70 KM/H (45 MPH). I travel all throughout Southern Alberta & Eastern B.C. so there's a good combination of flat highway and mountains. I usually use my cruise control at or just over the speed limit. I am extremely diligent in recording my travel with every fill and have been recording it all in an Excel spreadsheet for the past year and a half (work related) and decided to finally answer this question and figure it all out.

It shouldn't matter (I don't think) but I drive a newer 6 speed manual truck, V6. For a good base of averages I ran with higher octane for 23 tanks of gas versus the regular. I can't think of any other factors, I don't use A/C a lot and it would have been used to varying degrees between both regular and higher octane fills. The "regular" gas I get is usually from Esso at 87 Octane and the higher octane gas I get is again usually from Esso, "Supreme" at 91 Octane.

Okay, enough of the pre-amble... now for the results! I hope I did the correct calculations & conversions from Canadian to U.S. for all you folks in the states... If you find an error, please post it!

"Regular" Gas at 87 Octane
Average $/L: $1.180/Litre ($4.43/Gallon U.S.)
Average Economy: 13.76 L/100 KM's (20.52 MPG)
Average Cost of Gas: $0.16/KM ($0.26/Mile)

"Supreme" Gas at 91 Octane
Average $/L: $1.277/Litre ($4.79/Gallon U.S.)
Average Economy: 12.80 L/100 KM's (22.06 MPG)
Average Cost of Gas: $0.18/KM ($0.29/Mile)

So, what does all this mean? I found that the fuel economy is better with the higher octane by almost 1 Litre per 100 Kilometers (1.5 gallons per mile). On the opposite side though, the cost of gas was greater for the higher octane by $0.02 per kilometer ($0.03 per mile). So, even though I got better fuel economy, it was not worth the increase of cost at the pump. This information is not taking in to consideration any other factors such as the supposed cleaner engine, fewer emissions, etc... Just the bottom line with dollars.

I hope you find this information of interest if nothing else and feel free to comment on any of my findings. Happy and safe driving, no matter where your GPS takes you!

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Good info

Thanks for posting it.

I think the only time to by premium is when your car requires it, that is, high performance cars.

--
nüvi 3790T | nüvi 775T | Those who make peaceful revolution impossible, will make violent revolution inevitable ~ JFK

There is more heat content

There is more heat content in regular gasoline than high octane gasoline -- the more refining, the more is taken out.

Unless your engine was desined for high octane gasoling -- generally higher compression ratios -- you'll get better milage from regular gasoline under the same coditions and load. The higher compression ratio needs the high octane so the engine won't "knock" igninate the fuel before the spark plug fires. This anit-knock property removes some of the btu content from the fuel.

Your results may have had more to do with driving conditions than octane of the fuel. And by the way, using regular gasoline in an engine designed for high octane is a sure way to get in trouble. The other way around is no problem, just more expense.

One of the reasons diesel engines get better milage than gasoline engines is because the diesel fuel has more btu content -- less has been taken out of it in the refining process.

If an engine could use crude oil, it would get the best milage of all, but that won't happen.

It's really all just physics.

Wil

Vehicles Requiring Higher Octane

I agree. Most vehicles these days are still designed to run on regular gas.

Knock Sensors Have It Covered

I think all modern gasoline powered cars have knock sensors, so it doesn't matter. The control system will sense knock and dial back ignition timing to eliminate knock. I have/had cars that I ran on regular with no octane related problems. The knock sensors and control systems worked as they were designed to do.

The only thing octane will affect is maximum horsepower attainable. The higher the octane, the more timing will be allowed, the more HP the engine can make.

There is negligible energy content between regular and premium gasoline. Octane indicates the resistance of a fuel to auto-ignite and the rate of fuel burn. Higher octane fuel has higher resistance to auto-ignite and burns slower.

As far as the test results, it's probably too close to make any certified conclusions. I have been doing the same for hundreds of thousands of miles. Weather, driving conditions, etc. have tremendous effects. Even when using the same fuel grade, the variance from tank-to-tank was greater than what you posted as attributable to octane differences.

--
GPSMAP64s, Montana 600, GPSMAP60CSx (retired), fenix, Bad Elf, iPhone 6, iPad2, Yaesu VX-8R w/GPS, MacBookPro, all sorts of maps.

Bottom line is the fuel cost per mile driven

And by your example, $.26/mile vs $.29/mile... the $.03 @ 3400 miles = $102 - either in your pocket not being spent on fuel, or spent on fuel.

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*Keith* MacBook Pro *wifi iPad(2012) w/BadElf GPS & iPhone5 + Navigon*

And That's The Point

I guess that was the main point I was trying to get out of all this. In the end it's what's coming out of my pocket and wanted to know if the extra mileage would be worth the increased cost. I found it wasn't so all other aspects aside such as engine performance, etc... I'm going back to regular to save the dollars at fill ups.

Another thought

Although my 2008 Ford Taurus 6 cyl gives me a shade better mileage using regular versus high test gas. I do run a couple of tankfuls of high test thru about every 10, 000 miles. My mechanic says the high test helps to clean out any minor deposits in the engine and injectors.
If I don't run the high test thru I put in a treatment of "Sea Foam" injector clean with a tankful about every 15,000 miles.
All I know it's got 75,000 miles on the engine and runs like a top with nothing else done to it except routine oil change/filters every 5000 miles.

I average about 30.5 mpg on the highway and 23.5 around town with a lot of lights. I'm a speed limit freak so I tend to get reasonable mileage.
I probably run the AC about 90 % of the time.

--
MrKenFL- "Money can't buy you happiness .. But it does bring you a more pleasant form of misery." NUVI 260, Nuvi 1490LMT & Nuvi 2595LMT all with 2014.4 maps !

Octane Levels for Regular Gas

I have noticed that in Canada, REGULAR gas usually has an octane rating of 87, while in the US the octane rating for REGULAR is 85.0 or 85.5. On the other hand, PREMIUM was usually 91 in both countries and SUPREME was most often 93.

I have never owned a high-performance or luxury vehicle, and have only put PREMIUM in the gas tank by mistake sad I doubt if there really is any significant improvement in mileage or benefit to the engine with using a higher octane gasoline.

Perhaps it reduces emissions?

I dunno what "Sea Foam" is, but. . .

MrKenFL wrote:

My mechanic says the high test helps to clean out any minor deposits in the engine and injectors.
If I don't run the high test thru I put in a treatment of "Sea Foam" injector clean with a tankful about every 15,000 miles.

... I try to use fuel injector cleaner on my car every 10K miles or so. I don't know if that works out cheaper than using a couple tank-fulls of high octane, or if the efficacy is the same. For that matter, I have no clue whether it has any impact on my car at all.

Sort of like taking daily multivitamins I guess . . .

A larger factor is the

A larger factor is the addition of ethanol (reduction of gasoline) in the mixture. Significantly less gas mileage.

Fred

Good info, thanks

"Old cars need high octane (91) gas" I've heard that so many times but is it true or just a myth? I'm driving a Honda, year 2000 model. Does it help if I use 91 octane gas or is that just a waste of $. Just curious.

Not in my experience

FZbar wrote:

A larger factor is the addition of ethanol (reduction of gasoline) in the mixture. Significantly less gas mileage.

10% ethanol blends I've used don't make that much of a difference for me.

The difference is the price - as in Iowa, ethanol fuels get a break on state taxes and are about $0.10 /gallon cheaper - and my fuel cost per mile driven is less on ethanol blended fuels than non-ethanol fuel.

And since I've been using ethanol fuel in any number of cars - from a 1965 Buick to my present 2008 Saturn Vue, I have never had a maintenance issue above & beyond normal maintenance attributable to ethanol - EVER.

--
*Keith* MacBook Pro *wifi iPad(2012) w/BadElf GPS & iPhone5 + Navigon*

Different Grades of Gasoline

All these different grades and different blends for different markets adds to costs for suppliers, distributors and ultimately you and I.

There should be one gasoline and that will simplify production, distribution and reduce cost.

When you do your cost analysis, do it on the basis of cost per 1000 miles. The delta looks more significant than a couple pennies when done per mile.

--
GPSMAP64s, Montana 600, GPSMAP60CSx (retired), fenix, Bad Elf, iPhone 6, iPad2, Yaesu VX-8R w/GPS, MacBookPro, all sorts of maps.

Depends on the old car

If you have a high compression hemi or LS6, you want the higher octane.

But if you have a modern car it probably has a knock sensor and will accommodate variances in octane.

I had an '87 Saab with an knock sensor and it was rather neat to hear the knock for a little bit before the control system dialed the timing back. Went 200,000 miles like that.

It's up to you. Knock is noticeable. Can you hear it?

I also have two diesels and I can't get enough auto-ignition!!!!

chewbacca wrote:

"Old cars need high octane (91) gas" I've heard that so many times but is it true or just a myth? I'm driving a Honda, year 2000 model. Does it help if I use 91 octane gas or is that just a waste of $. Just curious.

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GPSMAP64s, Montana 600, GPSMAP60CSx (retired), fenix, Bad Elf, iPhone 6, iPad2, Yaesu VX-8R w/GPS, MacBookPro, all sorts of maps.

not sure

diesel wrote:

If you have a high compression hemi or LS6, you want the higher octane.

But if you have a modern car it probably has a knock sensor and will accommodate variances in octane.

I had an '87 Saab with an knock sensor and it was rather neat to hear the knock for a little bit before the control system dialed the timing back. Went 200,000 miles like that.

It's up to you. Knock is noticeable. Can you hear it?

I also have two diesels and I can't get enough auto-ignition!!!!

I don't even know what a knock sensor is. Are you referring to the rapid "ticking" sound of the engine when accelerating? If that is so, the answer is no I have never heard of that sound. I heard of that sound (rapid *tick* *tick* when accelerating) when driving back in the 80s.

Google search result says that my year 2000 Honda accord does have a knock sensor.

Knock Knock

When the car has an octane deficiency, it will knock under high load.

The knock sensor is usually bolted to the block or head and can hear the knock.

Knocking results from abnormal combustion. Normal combustion is when the spark plug ignites the fuel and a flame front moves across the air-fuel mixture until the fuel is consumed. Abnormal combustion, or knock, is when fuel ignites spontaneously as a result of the ambient conditions. So if it is too hot, as happens during compression and the initial normal burn, the remaining unburnt fuel may all burn at once, or explode, which makes that hammering sound. That knocking produces a rapid rise in pressure that is detrimental to the engine.

Knocking will sound like a couple lug nuts shaking around in a coffee can. Frequency and intensity correlating to load. More load, more knocking.

chewbacca wrote:

I don't even know what a knock sensor is. Are you referring to the rapid "ticking" sound of the engine when accelerating? If that is so, the answer is no I have never heard of that sound. I heard of that sound (rapid *tick* *tick* when accelerating) when driving back in the 80s.

Google search result says that my year 2000 Honda accord does have a knock sensor.

--
GPSMAP64s, Montana 600, GPSMAP60CSx (retired), fenix, Bad Elf, iPhone 6, iPad2, Yaesu VX-8R w/GPS, MacBookPro, all sorts of maps.

NO

If the motor in your vehicle calls for a lower octane do not use the higher octanes, you won't hurt anything but you wallet. If you have a vehicle that says to run the high octane try the lower octane and record you mileage, you may be surprised(depends what the climate is where you are). Also if you have a high octane vehicle that sits outside in the colder climates, like Chicago you may notice that the lower octanes make the motor run smoother on the initial start ups. The higher octane has a tendency to soak into the carbon(what ever you call it now days) and the motor runs too lean on the cold mornings.
Just my experience after being a GM mechanic for 35 years.
Unless you want to race the vehicle just use the lower octane of a reputable(if there are any) oil company.
My opinion.

--
Nuvi 765T

sorry

Someone could make a fortune inventing a personal methane gas catcher and storage, I could really go green with that invention and be self sustained.

Heck it may even drown out the knocking sound the engine may make.

I wonder what MPcu ft the car would get?

--
Garmin 38 - Magellan Gold - Garmin Yellow eTrex - Nuvi 260 - Nuvi 2460LMT - Google Nexus 7

OK

diesel wrote:

When the car has an octane deficiency, it will knock under high load.

The knock sensor is usually bolted to the block or head and can hear the knock.

Knocking results from abnormal combustion. Normal combustion is when the spark plug ignites the fuel and a flame front moves across the air-fuel mixture until the fuel is consumed. Abnormal combustion, or knock, is when fuel ignites spontaneously as a result of the ambient conditions. So if it is too hot, as happens during compression and the initial normal burn, the remaining unburnt fuel may all burn at once, or explode, which makes that hammering sound. That knocking produces a rapid rise in pressure that is detrimental to the engine.

Knocking will sound like a couple lug nuts shaking around in a coffee can. Frequency and intensity correlating to load. More load, more knocking.

but does engine knock normally happen when the car is in motion or does it also happen when the engine is idle?

Thanks to Jery too. Going back to 89 octane on my next refuel.

Knock

You will normally hear a know when you start to accelerate from a stop or slow down the try to speed back up.

--
johnm405 660 & MSS&T

knock is temperature and load related

I've tried higher octane for a mpg advantage in my Suzuki SUV but if there is a difference it is small.

I agree with the other points saying to only use higher octane if the manufacturer of your car recommends it. My bimmer can use regular but they recommend higher and I run 91 octane. My zuke is rated to run on regular but it knocks sometime when it is really hot and if I am towing something. So I use higher octane when I am towing and sometimes in really hot weather.

Knocking can potentially cause severe damage. The peak pressure can exceed what the engine is designed to take. Knock sensors help a lot (at the expense of power and efficiency) but not always enough.

Last comment, I have noticed on two Suzuki SUVs that large spark plug gap makes the motor more likely to knock. I don't know if all cars do this but if your car knocks unexpectedly you might try replacing or re-gapping the plugs.

I fibbed, I also want to comment on the high mileage question. Normal wear and tear tends to lower the compression in high mileage engines. But sometimes deposits can raise it. So usually I would think you would have less need for octane on a high mileage engine but occasionally there might be one that is still "tight" that has deposits that will knock and need more octaine.

Really last, when my engine knocks, I back off the gas and it gets better, sometimes stops. Lower load = less knocking in my experience. That can prevent damage until you can get some higher octane gas in the tank.

Jim

Your wasting your money

Your wasting your money putting a higher octane fuel in a car designed to run on low octane ie 87. Unless your engine is tuned to run the higher octane you will see no benefits to putting it in.

--
Nuvi 660. Nuvi 40 Check out. www.houserentalsorlando.com Irish Saying. A man loves his sweetheart the most, his wife the best, but his mother the longest.

I agree....27yr Ford mechanic

Jery wrote:

If the motor in your vehicle calls for a lower octane do not use the higher octanes, you won't hurt anything but you wallet. If you have a vehicle that says to run the high octane try the lower octane and record you mileage, you may be surprised(depends what the climate is where you are). Also if you have a high octane vehicle that sits outside in the colder climates, like Chicago you may notice that the lower octanes make the motor run smoother on the initial start ups. The higher octane has a tendency to soak into the carbon(what ever you call it now days) and the motor runs too lean on the cold mornings.
Just my experience after being a GM mechanic for 35 years.
Unless you want to race the vehicle just use the lower octane of a reputable(if there are any) oil company.
My opinion.

I agree and here is a good article
http://www.ftc.gov/bcp/edu/pubs/consumer/autos/aut12.shtm

--
All the worlds indeed a stage and we are merely players. Rush

Shell VPower FTW!

Shell VPower FTW!

"diesels" comments are right on.

87 octane is ok in my 2003 Passat 1.8 turbo. VW recommends premium (higher octane) but the car runs well, summer and winter on 87 octane (regular). If you want the to really feel the turbo boost, fill up with premium otherwise save your $$$

All of the later generation cars (electonic fuel injection) have anti-knock sensors.

If you had a car that was "knocking" at idle, you have a very serious problem.

Great info

d-moo70 wrote:

I agree and here is a good article
http://www.ftc.gov/bcp/edu/pubs/consumer/autos/aut12.shtm

I've been filling up 91 for the past year. Going back to mid-grade (89 octane) gasoline which is about 10 cents cheaper per gallon will save me around $3 to $5 a month. Not much but it adds up over time.

Thanks to all for your great information.

Gas requirement

I have always been told use the gasoline that your car require ,it save you money but ones in while does not hurt to fill it up with High Octane gas,it help clean up engine..One thing is for sure now that winter is on his way.never let your gas tank drop below half. Also it prevent moist and consendation to be mixed with your gas..

This kind of knock happens at max load regime

Engine knock, or ping, or detonation, will happen at high loads, near max loads, such as passing, accelerating, climbing a hill.

chewbacca wrote:

but does engine knock normally happen when the car is in motion or does it also happen when the engine is idle?

Thanks to Jery too. Going back to 89 octane on my next refuel.

--
GPSMAP64s, Montana 600, GPSMAP60CSx (retired), fenix, Bad Elf, iPhone 6, iPad2, Yaesu VX-8R w/GPS, MacBookPro, all sorts of maps.

Octane vs altitude

I have found that the higher the altitude, the less octane a car needs because of less air in the combustion chamber will cause the gas/air mixture to burn more slowly. Calgary, 3700 feet up, is a lot different than Illinois, which in my town is 730 feet, and down by the river it is only 525 feet. The octane choices here are 87, 89,(E-10), and 91. No matter. My owners manual states a minimum of 87 octane. In Montana and Wyoming, regular is around 85, but I choose to burn a mid-grade anyway.
It would be interesting if some one in the Gulf states would have different results than you.

--
1490LMT 1450LMT 295w

Fuel Cleaners

As far as fuel cleaning additives, most are already in the fuel as required by law for emissions.

However, there are a new class of fuel requirements called Top Tier. These are even greater fuel cleaning requirements. You can search this out. These fuels are for the new DI engines.

--
GPSMAP64s, Montana 600, GPSMAP60CSx (retired), fenix, Bad Elf, iPhone 6, iPad2, Yaesu VX-8R w/GPS, MacBookPro, all sorts of maps.

.

MrKenFL wrote:

If I don't run the high test thru I put in a treatment of "Sea Foam" injector clean with a tankful about every 15,000 miles.

I use a couple of ounces of Luca's top end in the tank with every fill. Clean the injectors, and lubes the fuel pump as well.

--
nüvi 3790T | nüvi 775T | Those who make peaceful revolution impossible, will make violent revolution inevitable ~ JFK

.

diesel wrote:

Engine knock, or ping, or detonation, will happen at high loads, near max loads, such as passing, accelerating, climbing a hill.

I got it now. Thanks for your replies.

For those who say . . .

that ethanol has only marginal impact on mileage, note that in a real world test, a friend of mine rode his 1300 cc 2006 fuel injected motorcycle on a 550 mile round trip course between South Dakota and Wyoming with his throttle locked to 70 mph (or as close as locking the throttle would allow twice.

Temperatures were similar (low 70s) and on one trip he used 10% ethanol and on the other gasoline without ethanol, but of the same (87) octane.

Using ethanol he averaged 39.2 mpg. Without he got 45.6. A rerun with ethanol yielded 39.1 mpg - and I suppose we can assume tat there may have been someresidual ethanol in the tank at the start of the ethanol-free run.

That means that displacing 10% of the gasoline with Ethanol resulted in a decrease of the mileage achieved by 16%.

In other words the ethanol reduced his mileage by more than it's volume so he actually burned more gasoline with ethanol than he did wiithout!!.

It doesn't help that ethanol is hygroscopic (which means it retains a lot of water over time), goes stale very quickly and such.

As to 'costs less', up where I live there is no price difference between ethanol and non-ethanol 87 octane fuels - in my home province (Quebec) Esso (Exxon) delivers only non-ethanol gas, most of the rest add ethanol.

So at least (as far as my motorcycle is concerned - I haven't run any tests on the cars) I get non-ethanol gasoline for an effective 5% discount relative to what I pay for ethanol gasolines.

Then, of course there is the fact that using ethanol pushes up the price of food. But lets not go there.

--
Currently have: SP3, GPSMAP 276c, Nuvi 760T, Nuvi 3790LMT, Zumo 660T

Very interesting

Thanks for taking the time to conduct your experiment.

I have to say I was never so happy as when traded in our older Sienna that required 93 octane and found out the new one only needed 87 octane. It is a nice savings over time.

I went to edit my post, but couldn't

So what I was going to add is in this additional one:

The OP's comparison merits the addition of a cumulative total for the extra cost of using 'premium grade' fuel in his car:

$3,000 over a 100,000 mile life of the vehicle - pretty significant given that the average price of a vehicle is about $30K.

Using 87 octane ethanol-free gasoline in place of 87 octane E10 would save him almost $5000 if the economy differential matches that experienced by my riding buddy - this in addition to the $3,000 saved by not using premium gasoline.

--
Currently have: SP3, GPSMAP 276c, Nuvi 760T, Nuvi 3790LMT, Zumo 660T

Ethanol

Ethanol has lower energy content than gasoline. Reduced MPGs is to be expected.

Ethanol is an alcohol, so it will remove water from the fuel system. Most gasoline additives, especially the winterizers, are alcohols, to remove water so it doesn't freeze and cause fuel starvation problems. So now there is ethanol in the fuel all the time, no need to add a gasoline fuel winterizer.

I was in waaaaaaay northern Canada for almost two weeks just recently and up there they advertise that gasoline does not have ethanol. I did get pretty good mileage up there. The gas stations did have plenty of winterizer additives available.

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GPSMAP64s, Montana 600, GPSMAP60CSx (retired), fenix, Bad Elf, iPhone 6, iPad2, Yaesu VX-8R w/GPS, MacBookPro, all sorts of maps.

Interesting

I would not have thought that you would get better mileage from the higher octane if the car was designed for lower octane.

The ethanol blending comments also match what I have seen. The e85 fuel gets very poor mileage as compared to full strength gasoline. This not offset by the "lower" per gal price. I don't own a flex fuel vehicle. But when I rent them, I buy full strength gas for my trips and return them with full tanks of e85.

Out of pocket

bramfrank wrote:

So what I was going to add is in this additional one:

The OP's comparison merits the addition of a cumulative total for the extra cost of using 'premium grade' fuel in his car:

$3,000 over a 100,000 mile life of the vehicle - pretty significant given that the average price of a vehicle is about $30K.

Using 87 octane ethanol-free gasoline in place of 87 octane E10 would save him almost $5000 if the economy differential matches that experienced by my riding buddy - this in addition to the $3,000 saved by not using premium gasoline.

All discussions regarding the different qualities of gas, engine knocking, engine cleanliness, etc. aside, it was interesting to find out that 1) the higher octane gas provided better fuel economy and 2) it was not worth the increased cost at the pump. Over the course of a month that 2 cents per kilometer difference adds up to an extra $100 out of pocket for the premium fuel. Add that up over a year and we're at $1200 just in lost dollars for fuel cost.

.

Keep in mind that the experience was that of the OP, in his specific vehicle and in the local environment.

It is likely that your results will differ. His vehicle might have needed a bit more octane to offset dirty plugs or throttle bodies.

--
Currently have: SP3, GPSMAP 276c, Nuvi 760T, Nuvi 3790LMT, Zumo 660T

YMMV

bramfrank wrote:

Keep in mind that the experience was that of the OP, in his specific vehicle and in the local environment.

It is likely that your results will differ. His vehicle might have needed a bit more octane to offset dirty plugs or throttle bodies.

Exactly. Theoretically, using a higher octane than the engine requires will result in no change in MPG.Higher octane fuel does not contain any greater energy. Using a lower octane fuel in a modern ICE that incorporates knock sensors will result in slightly less power and perhaps slightly less MPG due to the engine adapting to it.

Ethanol contains 30% less energy per volume than does gasoline. Therefore E10 contains 3% less energy and should result in a 3% reduction in MPG.

--
-Quest, Nuvi 1390T

Actually...

It takes 1.5 gallons of ethanol to produce the same energy as gasoline. See http://en.wikipedia.org/wiki/Gasoline_gallon_equivalent

--
nüvi 3790T | nüvi 775T | Those who make peaceful revolution impossible, will make violent revolution inevitable ~ JFK

..

I've seen 30% most commonly posted, but I'll buy 33%.

--
-Quest, Nuvi 1390T

.

Never mind...

--
nüvi 3790T | nüvi 775T | Those who make peaceful revolution impossible, will make violent revolution inevitable ~ JFK

Knock you can't hear causes damage.

My Harley and my Buick Regal 3.4l w/supercharger both recommend premium fuel per the manufacturers. There is a risk of engine knock damaging an engine if it is designed for premium fuel and you use lower octane. The undectable engine knock can damage your engine when it's always fighting preignition which pushes back against the motion of the pistons during compression. The cost on engine repairs far overshadows that of the fuel costs.

I ride 15K/year on my Harley. At $0.20 per gallon cost of premium over regular and 40mpg, that's $75/year for premium. I put about 12 gallons in my car every 2 weeks, 212 gallons/year * $0.20 = $42/year. Compared to at least $2K for an upper engine repair or $4K for a crankshaft replacement, that sounds penny wise and pound foolish to me.

--
Zumo 550 & Zumo 665 My alarm clock is sunshine on chrome.

A Harley and any car with a

A Harley and any car with a supercharger are high performance engines which certainly need premium fuel.

Anyone with just a regular car/SUV newer than the 80's only needs to get regular gas.

--
Nuvi 1350LMT, Nuvi 350, Nuvi 260, Garmin GPS III, Basecamp, Garmin Topo

Open the manual

Just Open the manual that came with your car, read the manufactures spec for type of fuel to use. That should answer all questions.

--
Using Android Based GPS.The above post and my sig reflects my own opinions, expressed for the purpose of informing or inspiring, not commanding. Naturally, you are free to reject or embrace whatever you read.

Avoid ethanol poisoning in your classic car

kch50428 wrote:
FZbar wrote:

A larger factor is the addition of ethanol (reduction of gasoline) in the mixture. Significantly less gas mileage.

10% ethanol blends I've used don't make that much of a difference for me.

The difference is the price - as in Iowa, ethanol fuels get a break on state taxes and are about $0.10 /gallon cheaper - and my fuel cost per mile driven is less on ethanol blended fuels than non-ethanol fuel.

And since I've been using ethanol fuel in any number of cars - from a 1965 Buick to my present 2008 Saturn Vue, I have never had a maintenance issue above & beyond normal maintenance attributable to ethanol - EVER.

Actually your 65 Buick has the most to lose using a ethanol blend.

http://www.americanrestomods.com/avoid-ethanol-poisoning-in-...

--
Using Android Based GPS.The above post and my sig reflects my own opinions, expressed for the purpose of informing or inspiring, not commanding. Naturally, you are free to reject or embrace whatever you read.

wow

This topic is beaten to death on so many car forums and myth busters and snopes have addressed it so long ago.

My German car requires 89 and no less, it states that in the owners manual. 87 is not a choice, it's twin turbocharged so only someone who leases would even dream of putting in 87.

My 1998 Nissan on the fuel door states "regular unleaded may be used when premium is not available." I've used regular its entire life and it's been fine. There is NO mpg benefit by using premium, that's not what octane measures. It measures a fuel's ability to resist predetonation, not mpgs.

Our 2011 GM vehicle specifically states that the motor which has direct injection is designed to use regular. If there is knocking or pinging when using regular, something is wrong with the motor and it should be brought in for service.

Anybody is free to use whatever fuel they want, but if a vehicle was not designed for premium, $$$ are being burned right out the tailpipe.

Higher Octane

I fill up on higher octane when I do a long highway run to clean out the engine carbons thats built up with local driving.

In 1978

I had a beautiful 1974 metalic gold Cougar which my dad advised me to use the higher octane gas. I trusted his advice because he worked on all the vehicles, even overhauling the engines. I had no clue why he advised it, I just followed it until I totaled the car. I was in my twenties and did not know what an "impact" driving in the first ice storm of the year would have. shock

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