What is the difference between using 87, 89, 91 gasoline? Does it really make a difference on the engine?

Answer 1

What occurs inside the engine is the piston compresses the space inside the cylinder. Typically when it hits the top (or close to the top) the spark plugs fires and forces the piston down. (aka power stroke).

Typically the higher the compression, the more power you can get. So you want to compress the piston as far up the cylinder as possible.

Lower grade fuels (ie 87 octane) will begin to ignite at lower compressions. Typically due to the residual heat, while higher octane fuels (91 octane) resist what's known as spontaneous/pre ignition. So mid and premium fuels allow for engines to compress the air fuel mixture more.

If your car doesn't have a high compression engine, then you can't take advantage of this, and you'll just be wasting your money, if you want to take advantage of this you must purchase a high performance engine or high compression engine. The manufacturer will typically tell you what grade of gasoline is required for that vehicle. Many mid and high end Hondas and Nissans now recommend 89 and 91 octane gasolines.

If your vehicle can take advantage of this, it will allow the greater compression of the air/fuel mixture and typically give your more power as a result.

To allow high compression engines to burn lower grade gasolines, manufacturers have placed knock sensors in engines to retard or delay spark so that your compression of air/fuel is not optimal. It allow the car to run, but you lose power and really wasted your money in purchasing the car because you aren't taking advantage of the engine's full potential.

Oh, and why is pre-ignition/spontaneous ignition bad. Well pre-igntion can occur anywhere inside the chamber and typically counter the direction of force that your spark generates. Typically it also results in "shock" waves as the multitude of flame fronts collide. This generates engine knock, and the shock waves can damage your piston and cylinder surfaces.

Answer 2

The differance is in the price. the higher the number the higher the cost. Big cars with big engines need the higher number to keep there engines from pinging. Pinging is a noise the engine makes when it excelerates or climbes a hill.
Most cars will run just fine on the lower number gas.

Answer 3

For the average daily driver, 87 octane is fine.
The more "performance" that you have, the higher the octane needs to be in order to utilize all the available HP.

A newer Corvette will knock on 87.

Answer 4

the higher the octane, the longer it takes to burn. therefore... based on my experiments with my truck, 91 octane gets better MPG. 91 octane is usually only 10 cents higher, so you'll have to get at least 10 gallons to see a dollar difference. the experiment is worth the expense.

Answer 5

basically it is the flammability of the fuel ,but in most new cars it does very Little to help performance unless your driving a caddy or high performance car like a vette or viper ,check your owners manual for the manufactures rating on the needs of the vehicle you have

Answer 6

I think so. Has to do with high performance engines. If you had a high performance engine I think you'd know based on what you paid for it. For the average car the lowest # is fine.

Answer 7

Those are octane ratings and yes they make a difference. Stick with whatever your car's manufacturer recommends.

Answer 8

89 octane burns cleaner less detirgent in it less carbon build up 91octane is manly used on bigger engine

Answer 9

the difference is how long they ;last. they are thicker than the next...