What's the difference of the 3 Gas grade: Regular (87), Mid-grade (89) and Premium (92/93)?

Question

Is the higher grade gas better for the engine?

Answer 1

Actually ahmaduhhs is wrong.

The three grades of gasoline is an octane rating. This is one of the most misunderstood values. The octane rating is actually a measure of resistance to ignition. The HIGHER the number, the HARDER it is to ignite the fuel.

So believe it or not, it's actually more difficult to burn Premium (92/93 octane) than it is to burn Regular (87 octane)

So the question is why do you want gasoline that's hard to ignite? The answer is you can put gasoline that's harder to ignite into a HIGH COMPRESSION engine. The higher your engine compression, the more "power" your engine will give your.

If the fuel began to ignite while the piston was beginning it's compression process you wouldn't get the full power from the fuel. In a typical gasoline engine the spark plug is at the top of the cylinder because you want to ignite the gasoline at the top to have the flame front push the piston down. If you have auto-iginition, flame fronts can develop along the edge of the wall or from the edge of the piston. This flame front typically act counter productive against the flame front that comes from the spark plug. As these flame fronts collide, you'll get shock waves, which is the Knocking you hear when you have a high compression engine using a lower grade fuel.

If your engine is not a high compression engine, it can not take advantage of the higher grade fuels, so you're just throwing your money away. If your vehicle is a high compression engine, it can use the higher grade fuels to give you more power.

If you have a high compression engine, you must use the higher grade fuels. Putting a lower grade gasoline in a high compression engine will cause the engine knock described above. The shock waves will cause pre-mature engine wear.

So to answer your question, if your engine is not a high compression engine, using the higher grades of gasoline is a waste of money. If you have a high compression engine, you should not use anything less that what the manufacturer recommends or you will damage your engine.

Answer 2

Higher octane is NOT "better" gasoline. Octane is a rating of the fuels ability to resist knocking or predetonation. This is important in some engines that have very high compression ratios or perhaps a turbo or super-charger. When you compress the air/fuel mixture it heats up. In a high performance motor the air fuel mixture is compressed more and thus it heats up more. The air fuel mixture can be heated up so much that it can actually combust before the spark from your spark plugs goes off. This is called knocking because of the sound it makes. It's bad because the fuel is burning and pushing down on the pistons when it is still coming up.
High octane gasoliones are designed to resist combustion due to these increased pressures and temperatures. The higher the rating, the more resistant it is. Your car will be designed to operate using a specific octane rating. If your car requires regular gasoline, there will be absolutely no benefit to using a higher grade fuel. Conversely, if your car DOES require high octane fuel, using a lower grade could be very dangerous and cause damage to your engine.
The bottom line, uses the grade of fuel that your manufacturer reccomends. IF they say you need 87, don't waste your money on high octane.

Answer 3

Those are octane ratings. The LOWER the rating the MORE explosive that gas is (meaning it combusts at a lower temperature). The HIGHER the rating the LESS explosive that gas is (combusting at a higher temperature). Example-racing fuels are generally 105-120 octane.

FAQ-"Why does that seem backwards?" You would think higher octane would be more explosive, but it's just the opposite. The reasoning for this is that by controlling the combustion temperature (making it higher) we can run the engine faster and more precisely. 2 benefits of this are basically eliminating the chance of a "misfire" and not leaving any fuel residue behind.

Another benefit to premium gas is it's cleaning ability. It generally has more detergent cleaners for your fuel system in it (like Amoco Ultimate). Also, by running the engine slightly hotter, it burns off carbon deposits and keeps your fuel injectors cleaner.

Have you ever bought a bottle of fuel injector cleaner? All that is doing is raising your octane even more and adding more detergents to your fuel.

An auto test mechanic for Ford told me once that if you run one tank of premium per month you'll likely double the life of your fuel injection system. I run premium all the time because it increases my mileage by almost 4mpg!

So, in answer to your question, yes it is better, but depending on your vehicle, it may not make that much impact on your mileage. It will definitely help your fuel system in the long run, though.

Answer 4

If they have two tanks for gas they should blend. Legal ratio is 65:35 but most of gas stations blend 70:30 (regular:super) I dont know why they are in business? Why not sombody from tecq or tda check them ? I am tech since last 15 years and owner usally ask to go beyond the limits.

Answer 5

the #'s represent octane levels in the gas the higher the number the more refining went into the gas ; the better it burns

Answer 6

I learn a lot from the answers,
Thanks Arctic for you question.
We all should ask question like this , which is educative and interesting also.