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factoryjoe's avatar

Is there really any reason to buy 89 octane gas over 87?

Asked by factoryjoe (59 points ) June 9th, 2008 from iPhone

besides saving a few pennies per gallon at the pump, is 89 octane gas better for the environment or better for engine performance? Anyone really noticed a difference?

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14 Answers

girlofscience's avatar

I heard from a potentially reliable source (50/50) that half of the time, the people who put the different grades of gas in the pumps don’t even do it correctly. So, if you buy regular gas all the time, you’re probably actually using premium gas some of the time. Likewise, if you bought premium gas all the time, you may be using regular.

Personally, I don’t know anyone that’s ever used anything but regular. Unless their car requires diesel.

Cardinal's avatar

Only if your cars engine whines and crys and refuses to run properly, such as my older Mustang.

whatthefluther's avatar

I always went for the higher octane for my motorcycles strictly for better performance and smoother running engines. It made a noticeable difference with my bikes.

reed's avatar

Unless your vehicle specifically requires premium (i.e. a high compression engine or turbocharged or supercharged), there really is no benefit in running the higher octane so save your money. 89 octane is more mid-grade rather than premium and really only serves the purpose of suckering people into thinking their car will run better with it. I have a supercharged engine car and it needs 91 octane to run well and will ping a bit with 89.

XCNuse's avatar

If you have a performance vehicle (usually a european made car; sorry this doesn’t include what i personally call “performance cars”), like a Mercedes, BMW, Jag… basically any expensive european car, then it will most likely take a higher octane gas. If you put the specific type of gas you are supposed to, then your gas mileage should remain where they say it is, and will run much cleaner and smoother.

If you put the wrong octane in a car, say a lower octane in a higher octane required car, well… not a good idea, but higher octane cars run at higher compressions, thus require the higher octane gas to run properly, if you run under octane, then chances are it won’t run clean, and will put a dent in your gas mileage.

If you put higher octane in a low octane car, then you just plain shattered your gas mileage for the most part, and are an idiot for paying the higher price in the first place.

edmartin101's avatar

A lower octane gas tends to build a carbon film on your cylinder heads. Usually, you won’t notice the difference in engine performance for the most part since most of your driving occurs in the city. The carbon film inside your cylinders will be confirmed if you open the engine to replace your head gasket when you rebuild your engine head or when you want to do an engine overhaul. Only then you will see what the different octane gas will do to your engine. So if you plan to keep your vehicle for over 10 years then it would be a good idea for you to use the higher octane, otherwise is not worth it. The ping that some people notice in their vehicles happens because the compression ratio changes due to the carbon build up which affects your timing chain performance.

ninjaxmarc's avatar

I noticed the difference in power when using it in my v8 truck. It felt sluggish with 87 over a higher octane.

Definitely high performance cars require a higher octane. Higher compression, forced induction cars such that are turbo or supercharged.

factoryjoe's avatar

These are great responses so far… but should I presume that when people say “higher” octane they mean 91? Or is 89 actually a considerably higher octane than 87?

And why the difference in price? What accounts for that? Extra processing?

gooch's avatar

you may get better performance and better gas milage on the octane gas

XCNuse's avatar

@gooch, not if your car is made for 87; then it can’t combust the higher octane fuel which is used because it has a higher compression which other “performance” cars’ engines do.
You would in a sense be ruining your mileage because it can’t combust as much gas because it doesn’t combust until there is more compression.

There are reasons why engineers set cars to run on 87 octane, vs 91 octane, and it isn’t to set the poor vs the rich, and yes, it does go beyond compression ratios etc.

Just put what your car is supposed to have in it, and it will run correctly, otherwise you’ll be hurting your car severely in the long run (and wasting your own money for later expenses)

edmartin101's avatar

@factoryjoe I know we can’t rationalize the price difference in the higher octane between 87 and 89, but you do get the benefit of a higher horsepower due to the volatility of the fuel. It’s all about marketing to make people believe they are getting the ultimate pie. Yeah there is a little extra processing to get rid of hydrocarbons content in gasoline, but is not much of a difference because millions of gallons are processed at a time, so the cost difference to the refinery is minimum.

waterskier2007's avatar

i drove my grandpas viper to prom and had to fill it up with premium, so on performance cars, it matters, on everyday drivers, no i dont think it matters

Noel_S_Leitmotiv's avatar

Cars with engines designed to run on premium gasoline will only operate at maximum efficiency (power) if premium fuel is used.

Modern cars have knock sensors (actual tiny microphones tuned to hear knocking due to detonation usually caused by using lower than recommended octane) When knocking is detected the sensors tell the engines computer to retard the ignition timing slightly to eliminate the knocking. Output likely will be noticeably reduced.

Using lower than recommended octane wont harm a modern engine but it will compromise performance.

john65pennington's avatar

Police motorcycles only use premium gasoline.

So, I assume there is really a need for it.

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