If my car is designed to use 87 octane gas, will my mileage improve if I use 89 or 91 octane?

Question

I heard some people say that it's a waste of gas to do that, but other people said it would make the car run better.

Answer 1

you will get more mpg, but not enough to make up the price difference.

Answer 2

NO it won't help at all. High octange gas is not better than regular gas.All grades of gasoling must contain the same detergents and additives by law.

Most people don't understand what the octane rating even means. It is simply the ability of the fuel to resist detonation. Detonation occurs during the compression stroke when the air-fuel mixture is being put under high pressure and temperature. If you compress the mixture enough it can combust before the spark plug ever has a chance to fire. When this happens the piston has to fight the explosion as it comes to the top of it's stroke and then goes back down again. As you can imagine this is very bad for your engine. High octane gasolines are designed to resist this pre-detonation.

That being said, your engine is designed to operate using a certain specific octane rating. If your car is designed to run on 87 octane, that means that you should never have this problem of detonation if you use 87 octane. Using a higher octane will not do anything at all. The engineers have made sure that the car will work perfectly using 87.
The only cars that need high octane are cars with very high performance engines that generate much higher temperatures and pressures. Cars that have turbo chargers or superchargers would need to use high octane gasoline.

If your car is designed to run on 87, you are completely throwing your money away if you spend money on high octane gasoline. You won't get better milage, it won't burn cleaner, and it isn't any better for the environment.

Answer 3

Not necessarily. Best way to find out is fill up with each octane, drive under similar conditions and do your numbers. In general, using the least octane without noticing a decrease in performance is the way to go. As engine gets older and carbon deposit starts building up it may be necessary to go the higher octane to avoid engine knock. If you don't have this problem, stay with the 87 octane... where I live, it can be a difference of 15 to 20 cents per gallon.

Answer 4

It will increase your gas mileage a bit because a gas with a higher octane will have a higher content of inert material which will burn at a higher temp. It kind of is a waste of money though because the amount of money you waste on the higher cost of gas will kind of come out the same as what you are using right now. If you are doing it for the environment, it's cool, but it's to save money, it's not worth it.

Answer 5

Unless your car is in some way a "performance" vehicle i.e. has a hightened compression ratio, you most likely will not notice any difference in power or fuel economy by switching to a higher octane fuel. Higher octane fuels are more stable, which is why they need to be used in cars with higher compression to avoid pinging/knocking.

Answer 6

If you do get better mileage the amount of gas you save will not add up to the extra amount your paying. It will make your motor run better and cleaner though. I know a mechanic that runs premuim in his 4 banger sunfire. He says its just better for the motor. I've also heard that running premium can lower milleage, but I dont know if its true.

Answer 7

louis g is right, cars are tuned for a specific octane level. i've heard it might even be bad if you fill up with a higher octane than what ur car is meant for

Answer 8

No. If your engine doesn't need it for anti knock properties, you're just wasting money. Back in the old mechanical and carbureted days it would make a difference but not anymore.

Answer 9

It will help by maybe a mile per gallon but it will make your engine run better and cleaner...

Answer 10

as far as mpg goes its not worth the price to switch, but it is far better for your cars mechanical parts.