Myth's about Premium Gasoline

DavidB · 03-27-02, 08:17

by David W. Bynon

Many people believe that “premium” gas is the best gas. Not true. Premium simply means “premium price” for higher octane. Octane is a simple measurement for a gasoline’s ability to resist engine knock, a rattling or pinging sound that results from premature ignition of the compressed fuel-air mixture in one or more cylinders.

Most gas stations offer three octane grades: regular (usually 87 octane), mid-grade (usually 89 octane) and premium (usually 92 or 93). The ratings must be posted on bright yellow stickers on each gasoline pump. The misnomer about octane is that the higher the rating, the better or more smoothly your car will run. In fact, premium gas can be bad for your engine if it was not designed to run at a high-octane level.

Although it may seem that the term “premium” or “high octane” implies that more energy is available, premium gas does not produce more energy than regular or mid-grade fuel. The octane grades are designed to accommodate engines with different compression ratios. High compression engines, found in most performance cars, require a fuel that burns efficiently at a higher temperature. That’s what premium fuel does, it burns hot under high compression. In a normal engine, premium fuel does not burn completely, resulting in excess carbon build-up and carbon fouling of the spark plugs. The end result is a less efficient engine that requires tune-ups more frequently. Oh, yeah, did I mention it also wastes money?

The only time you might need to switch to a higher octane fuel is if your car engine knocks when you use the recommended fuel. This happens to a small percentage of cars. Check your owner’s manual to determine the right octane level for your car. Regular octane is recommended for most cars. However, some cars with high compression engines, like sports cars and certain luxury cars, need mid-grade or premium gasoline to prevent knock.

Bugatti · 04-30-02, 12:41

Thanks for opening this David B.

Premium Gasoline has more additives than regular, it's better for your SPORTS car! Also switching gasolines is better for your SPORTS car. A friend of mine in France is a Car evaluator and knew my M3 and every bug in it. He told me to rotate between 3 different gas chains because each chain offers seperate cleaner additives.

I will have to dig up info to back up my claims. But sources aren't some kid down the street. The reason why I mention 'sports' car is that old Chevys tend to run better of regular. So DavidB is correct, but performance machines, especially foriegn cars were design to run on much higher octane, refined petroleum.

I dont want to flame, but would like to get the right info.

Feel free to rip my finds to bits!

04-30-02, 01:28

I agree with that statement a lot. We always used to fill our 95 intrepid with 91 octane and occasionally 93, and 89 was recommended. Now it gets terrible gas mileage and runs very poorly after 68k miles. The dealer finds this to be very strange. I blame it on the use of high octane gas.

Jngrbrdman · 04-30-02, 01:36

So are the things I've heard about gas milage and how you get more of it with Premium untrue? I personally notice a much better gas milage with a higher octane fuel. Of course, I'm fairly sure that my GSR was designed for use with premium fuel. It says so on the guage.

Do octane boosters do anything for your car really? What about those fuel additives that say they clean up the system? Any good?

FLAWLESS · 04-30-02, 01:54

Quote:

Originally posted by Jngrbrdman
So are the things I've heard about gas milage and how you get more of it with Premium untrue? I personally notice a much better gas milage with a higher octane fuel. Of course, I'm fairly sure that my GSR was designed for use with premium fuel. It says so on the guage.

Do octane boosters do anything for your car really? What about those fuel additives that say they clean up the system? Any good?

I also get slightly better mileage with 93+ in my Civic. I'm running nitrous so I have no choice but to run high octane to prevent detonation.

Octane boosters are mostly garbage. Nitrous express makes one however that gave me 3 hp at the wheels on the dyno, on the juice. But for naturally aspirated, they're a joke.

Chevron Techron is the way to go for fuel system cleaners. I add a bottle every time I do an oil change. Most ppl I know swear by it.

medic · 04-30-02, 02:02

Quote:

Originally posted by Jngrbrdman
So are the things I've heard about gas milage and how you get more of it with Premium untrue? I personally notice a much better gas milage with a higher octane fuel. Of course, I'm fairly sure that my GSR was designed for use with premium fuel. It says so on the guage.

Could this just be becasue you aren't reving as hard to accelerate since you are now using the gas your car was designed for? Honda engines (read all acuras) are supposedly high compression engines so they require the higher octane gas to run properly and to get the HP advertised.

Dave C. · 04-30-02, 05:10

I agree 100% with what David said. I have heard the same info elsewhere, I believe ASE was one of those sources. I also never thought to rotate brands, but as far as premium having more additives I guess it must in order to raise the octane rating. Also, I use Techron every 3k as well, the Red Line stuff isn't too bad either.

blkZ28Conv · 05-01-02, 05:40

Quote:

Originally posted by FLAWLESS

Chevron Techron is the way to go for fuel system cleaners. I add a bottle every time I do an oil change. Most ppl I know swear by it.

I agree that gas line cleaners are a great additive to use every 3000 miles or oil change. I use Seaform or Techron but add these products just prior to the next oil change. The reasoning: these product basically flush and dissolve deposits which the majority are burned during combustion but a little is also washed into the oil and filter. But be careful for those drivers that have not done these procedure routinely. You could dislodge some deposits that may actually block a fuel injector. This is highly unlikely because today's gasolines all have some form of detergent and excessive build-up is rare if the car is in proper condition ( timing, plugs, etc)

joed1228 · 05-01-02, 06:00

I use the higher octane gas for speed.

My first two tanks were the middle grade and it was all fine and dandy. My buddy suggested that I use the higher grade, when I got on the gas pedal I could feel a slight difference.

It also says in the book that I need it to run the car so I'll just keep the motor in one peice.

My buddy has a 1998 Dode Dakota 5.9 360 cubic inch motor and it suggests that he only use 87 octance. Talk about having it easy eh?

carguy · 06-01-02, 06:19

FYI - if your car doesn't have electronic mgmt, you need only an octane level that prevents pre-ignition. More octane will only coast you money. However, if it DOES have electronic management with knock sensors, then you may not be getting full power - and in this want to clarify what David said.

Some engines are designed to make their power with a minimum of 93 octane. This is true of my BMW, for example. I can only get 91 octane here in CA. I never <b>hear</b> the engine knock - this is because the computer hears it first (via the knock sensor) and retards the engine's timing from its power-optimal setting to one where it no longer pings. I have access to 100 octane fuel - ocassionally I buy a half-tank (which gives me about 95) . It takes a little while for the computer to advance the timing - but it does, and as long as it doesn't detect knock it will advance it all the way to the optimal setting for power. In the M5, this makes a a NOTICEABLE difference. Interstingly, in the Porsche Turbo, it does not.

Do NOT use the car parts store "octane boosters" - they are a sham, and (according to Steve Dinan, one of the most respected BMW tuners) they contain some harmful additives. Increase octane by buying it at the pump if you can, or with toluene (see The Rocket Fuel FAQ )

As far as higher octane fuels HURTING your engine, or causing it to delvier poorer fuel mileage - I am aware of no reason for this. It may be a waste of money, but I don't believe there is any harm in running it.

jamesp · 06-05-02, 11:14

is this any good? if any one could give me some info on whether of not the rocket fuel would be benefitial for a MB 97 C 280 i would appreciate it. i like Chevron, but for some reason, all of the Chevrons near D.C. are now Citgo

blkZ28Conv · 06-05-02, 11:33

Octane effects volatility which means it effects combustability.The usage of octane is to decrease volatility of the fuel in higher compression engines in order to prevent pre-detonation ( knock)If your car is not rated to run higher octane fuel you are not only wasting money but also polluting the environment. All the unspent fuel is sent through the exhaust and may over- load the ability of the cat converter to neutralize.

Furthermore, higher octane does not translate into increase power unless the usage of a lower octane fuel creates knock and causes the ECU to retard timing. If your car runs prefectly on 87 octane it will not improve your performance by using 93 octane. In some cases as stated previously may decrease performance. Sorry..