Regular unleaded vs premium

[f_399]

I used premium the other day and will stick to it for about 2 full tanks then switch back to regular unleaded

 

Will there be any difference if i stay with premium?

[supreme_style21]

A lighter wallet.

 

Thats it.

[joey b]

I notice better mileage with premium. About 20% better. Select gasoline companies also add things to their premium gases such as fuel injector cleaners and probably some dehydrators as well. The results of that are cleaner fuel systems and combustion chambers. You should also get a longer life out of your O2 sensor since the fuel will burn cleaner.

[Guest TurboSedan]

i used low-grade (85 octane here) with my 3.1 MPFI engine and it ran great with it and i put ~120,000 miles on it using low grade. i'd say 87 should be fine for a 3100 but i'd like to hear what other people have to say...

 

the price of gas is a real bitch right now ecspecially when you deliver pizza for a living :?

[supreme_style21]

You're gonna save more money by buying a bottle of HEET and a can of Seafoam then.

 

The cars are designed to run 89 or 87, I don't remember. Anything above and beyond that isn't really helpful.

[THe_DeTAiL3R]

87 is "regular" .. we don't even have 85 over here. I agree with the crazy price premium is reserved for the L67s

[sonyman87]

Theory of mine. if you see an error i made please let me know.

 

#octane(power) per dollor

87 / $1.80gal = 48.33 higher the better

89 / $1.90gal = 46.84

93 / $2.00gal = 46.50

 

lets compair

 

If i had $20 to spend on gas which one will get me further per $ amount

answer is 87 believe it or not

 

$20 / $1.80gal = 11.11 gallons * 87 = 966.66 higher = better or more "power per $"

$20 / $1.90gal = 10.53 gallons * 89 = 937.17

$20 / $2.00gal = 10.00 gallons * 93 = 930.00

 

in another aspect of price

say the price gap was different

 

if 87 was 1.80 and 93 was 1.90

then

87 / $1.80gal = 48.33

93 / 1.90gal = 48.95 <-higher then 87

$20 / 1.80 = 11.11 gallons * 87 = 966.66 higher = better or more "power per $"

$20 / 1.90 = 10.53 gallons * 93 = 979.29

then 93octane would be the wiser choise

 

 

These are NOT nessasarily realworld figures. All cars will respond differently under different driving conditions. You should try driving with different levels of octane for 3 gas tanks each level and figure your average MPG per octane. Then use the avg MPG# in place of the Octane# figues above to get better #'s. Dont forget to adjust for price to realworld prices

[sl3196]

Damn this supercharger!

[f_399]

what do those numbers mean? 87 89 93 ?

 

so the higher the number the slower it burns gas? better gas mileage?

 

any preference with gas station?

[sonyman87]

what do those numbers mean? 87 89 93 ?

 

so the higher the number the slower it burns gas? better gas mileage?

 

any preference with gas station?

those numbers 87, 89, 93 is the octane level. In terms of energy the higher the octane chains the more power is stored. all gas stations follow the same set of guidelines/standards for gas. some stores like shell and BP use addatives to their gas to improve its "performance" a marketing thing more then anything.

[GnatGoSplat]

what do those numbers mean? 87 89 93 ?

 

so the higher the number the slower it burns gas? better gas mileage?

 

any preference with gas station?

 

It's an anti-knock rating.

Higher octane fuel has LESS energy and therefore less likely to pre-ignite under higher compression.

 

Under higher compression, 87 octane can pre-ignite. That means it can explode even before the spark plug fires. The cylinder pressure alone can cause it to ignite. This is bad, it makes the engine knock and run like crap. The higher the octane, the less likely it will spontaneously pre-ignite under high compression. That's why it's necessary on forced-induction engines or engines with higher-than-normal compression.

 

The only way to know for sure if you'd benefit from higher octane is to run a diagnostic scanner on your car and monitor Knock Retard. Some knock is sub-audible, and the ECM will detect it and retard timing so that you never even knew the knock occurred. With a scanner, you can see if that's happening or not. If the ECM hardly ever detects knock, you won't benefit from going to a higher octane. On an unmodded car, it's best to use what the manufacturer recommends.

[Grand Moff Joseph]

My grandparents were the first owners of my car, and drove it until 2004. From day one, my grandpa insisted on putting 91 octane in the car all the time. Now, maybe he was wasting his money, but he akways reported great gas mileage, and upin getting the car seviced, the service tech said that the fuel system was as clean as a whistle.

[94CutlassSLCoupe]

I run 87 octane exclusively in my 3100 Cutlass...NO point in using higher octane gas, IMO...I have gotten 32 mpg before on it...and run a 16.5@83 1/4 mile using Mud and Snow radials (I have a traction problem )

[ursus]

You will see absolutly no increase in power or mileage by switching to premium, in fact you will normally see a little poorer as indeed higher octane fuel has less energy in it.

 

Higher octane fuel will resist detonation / knocking allowing you to either raise the compression ratio or advance the timeing or both. Detonation is a condition when the flame front speed exceeds mach and casues a shock wave to form and hit the piston/chamber. This is really bad for the piston and creates a lot of additional heat. the added heat can cause pre-ignition where the mixture ignites before the spark plug fires leading to additional detonation more heat etc. Higher octane fuel burns slower which is why it resists detonation better.

 

If you raise the compression ratio or you advance the timeing those 2 things can and will increase the power and mileage but premium gas in itself does nothing.

 

Some engines, not 2.8/3.1's et al. , can actually adjust the timeing automatically by advanceing it until they detect knock then backing off slightly and they can take advantage of premium gas, ours cannot.

 

Some engines actually run worse, the 8.1 litre for example had some problems early on, the pudr would intentionally advance the timing after start up to cause knock momentarily to test the knock sensor/system. Running premium gas would cause it not to knock during the self test and the pudr would assume the knock sensor was toast and go into rich mode casueing krappy mileage/performance.

 

If you notice a big dif like 10% better mileage then it is because something is really wrong with the engine to start with which is causeing knock and the pudr is retarding the timeing to prevent this. Heads that were milled rasieing compression or a ton of carbon which raised compression and makes the chamber run hot, a timeing belt that has slipped one tooth so the timeing is to advanced for examples.

 

If the engine is running normally tho then save your money, Premium gas does nothing unless the engine is retimed or built to take advantage of it

[jeremy]

in my cutty I just ran 87 octane without a problem. In my 86 Fiero with the v6 I only ran Shell 94 because there was a noticeable difference in performance and gas mileage between the 87 octane and the Shell 94.

 

I am currently running the SHO on Shell 94 too because it requires premium fuel.

[EurosportZ34]

when gas was cheaper i usually would run mid-grade or premium in the Z34 and Euro but when gas is so high like it is now regular is about all that i can afford!

[jeremy]

I just paid $2.65/gallon for Shell 94 this morning....

[GP1138]

It's pretty much a waste to use premium in cars designed to run on 87. You'd get the same advantages running some STP fuel system cleaner through your tank every couple months, honestly.

[Vegeta]

The only reason any of us has to run premium to get better gas milage is because of the operating condition of the motor. THe EGR loves to put carbon deposits all over your intake valve and combustion chamber. These deposits will mess with your fueling, and as such, can cause your motor to knock on mid grade when mid grade on a clean motor will run awesome. If you have poor milage, run the top engine cleaner through your injectors, vacuum line to clean the motor (follow directions on 60V6 or ask and ill post it again), replace the O2 sensor, and check your plug gap and wire condition.

 

I tune all my chips for midgrade unless its a custom tune on something that is high compression. I have had a 12:1+ compression motor run on regular gas, and another on mid grade. Difference being displacement and headers between the two vehicles. Anyone running premium on a stock motor is definetly throwing money away.

 

Gas stations put the same detergents in all grades of gas.

[ursus]

....Gas stations put the same detergents in all grades of gas.

 

You are correct, detergent content is mandated by the EPA, never understood why folks think big oil does would do more then the minimum req'd which is the same for all grades of gas. Have you ever seen big oil advertise that premium gets, better mileage, more power, burns cleaner, has better aditives,,, the reason they don't advertise any of those things is because it would be false.

[THe_DeTAiL3R]

I like how some of them (I think Shell?) has "bronze, silver, gold" next to the 87/89/91 LOL it makes me want to buy "gold" gas for my car when I put only crappy "bronze" LMAO.

[sl3196]

I like how some of them (I think Shell?) has "bronze, silver, gold" next to the 87/89/91 LOL it makes me want to buy "gold" gas for my car when I put only crappy "bronze" LMAO.

I think that is Amaco (or something like that) at least in the states it is.

[GnatGoSplat]

I like how some of them (I think Shell?) has "bronze, silver, gold" next to the 87/89/91 LOL it makes me want to buy "gold" gas for my car when I put only crappy "bronze" LMAO.

 

Yeah, there are some that call it something like "regular, plus, and ultra".

[5speedz34]

I just paid $2.65/gallon for Shell 94 this morning....

 

Damn! It was $2.35 up here.

[Dannymik]

Our computers are tuned for 87 octane (N/A that is)...thats what I do with the exception of some Chevron fuel system cleaner at every oil change.