Which gas is better for traffic driving 87 or 91?

Question

My car manual says it can run on 87 but for full performance use 91. I do alot of freeway traffic driving. Which gas would give me the best MPG?

Answer 1

If your car says that it will get better performance with 91 octane gasoline it means you've got a vehicle with a high compression engine.

High compression engines will give you more power if you use the 91 octane. (For vehicles not designed as high compression you will so no difference)

Since your car manual says it can use 91 octane, the engine has a knock sensor to retard spark when you use the cheaper gasoline. Basically firing the spark plug at a point where it is sub-optimal for performance, but prevents the shock waves that occur from pre-ignition (or engine knock)

In terms of MPG for your vehicle, there will be a small performance boost with 91 octane. The boost will come in terms of a combination of better MPG as well as more power for your vehicle.

In traffic you won't see much of a performance boost at all with 91 octane vs 87.since you're engine will be idling most of the time.

Doug is incorrect, there is a difference with octane values. However you must have a vehicle that can take advantage of the octane differences. Octane levels actually discuss the ability for fuel to combust. Believe it or not, the higher the octane number, the less likely the fuel will combust. The reason you want a higher octane number is that you can increase the piston's compresson before what is known as spontaneous or pre-ignition. If your car is not a high performance vehicle it can not take advantage of this and thus one would see no difference.

RalphW has the best idea in terms of how to determine what is best for your vehicle. Do an experiment. But if you're stuck in commuter traffic, I'd bet the performance gain will be minimal.

Answer 2

A lot of misconceptions of what an octane rating is. If your car runs fine with 87 and never knocks, keep it. Octane rating has nothing to do with adding power or performance. Not to say that the gas itself isn't higher or lower grade. Octane, is basically a rating used to determine knock/anti-knock qualities. Lets say you have a high compression race type engine. You may need and octane rated fuel of 103 to 110 to keep it from knocking. You can buy a poor quality gas with a 103 rating and your car will stop knocking, or you can buy a high quality gas with the same 103 rating and it will still stop the knocking. So, just because the octane rating is higher, that doesn't mean anything as far as power, performance or better gas mileage. All it is letting you know is that if your engine is knocking with 87 octane rating, you may want to jump it to the next higher rating. This way, no matter which gas station you fill at, you can fill the correct gasoline that you need. Now, as with most gas, higher octane probably does come with better fuel. But you still can buy better fuel at the same 87 rating, and come out better than before. Octane rating is just that, an anti-knock rating. More higher octane doesn't make horsepower or better gas mileage. Better fuel does.

Answer 3

If I were you, I'd keep track and calculate your MPG. First do a tank with 87. Use your odometer or mileage counter to keep track of how many miles your travel before your next fill-up. Do that a couple of times and track all your results.

Then do it all over with 91. In about two months, you should be able to see the difference for your car. Then you can calculate, based on avg gas price differences, whether it is worth it or not to use 91.

Answer 4

Octane numbers are just a ploy employed by car and gasoline manufacturers to coerce customers into purchasing more expensive fuel. The truth is that, unless you drive a hybrid or a much older vehicle, the difference between standard, regular fuel (87), plus (89-91), and premium (93-94), is really quite minimal.

Answer 5

87 will just make your car run okay but if your engine can run on 91 than that's what you should use because your engine is know running at its most efficient.

hear is what you should do. run your car until to fuel gauge ses empty then when you fill up your tank zero out your trip odometer and fill up your car with 87 then drive until your gas gauge ses empty and record your mileage next fill up with 91 and zero out your trip odometer and drive until you reach empty and know you can compare you data and see what octane fuel is giving your car better mileage.

Answer 6

The latest research, finds no significant difference in MPG savings between the various types of gas.

Nonetheless, the best way to find out is to try both types of gas.

Answer 7

Ethanol isn't as useful as gas. including it actual decreases the quantity of power you get in step with quantity. i'm uncertain on the subject of the octane numbers, yet i think of you're backwards on the commencing up. Ethanol has a decrease octane, and whilst further lowers to octane of gas.

Answer 8

The slower you drive the less gas you'll use or just don't peel out after you stop so that way you use less gas if you don't peel out.

Answer 9

that would depend on what kind of vehicle you have and what kind of fuel it has had in it . how much you want to spend on gas