That's unrelated to octane. It's a lubrication thing. Do a forum search on "premix" and/or "OMP" for more information.

 

People take out their pumps on S4's alot because of being paranoid of failure. Also because you will be using clean oil instead of dirty oil from your engine. I have a TII s4 with a large street port that i premix and run 93 octane in, i have a TII s5 that i dont premix and run 93 in. its kinda preference only the s5 is hard to do since its an electric pump not a mechanical and the ecu will notice no oil and put you in fail safe mode

 

well actually a significant amount of pre-mix in the gas lowers the octane level of that gas.

 

how much would me a signifiecant amount?

 

A lot. You'd have to way overdo it to have anything to worry about. I hear your car would also smoke and get worse gas mileage, but otherwise I don't think it really hurts anything. Unless I'm mistaken (and I might be), I think Icemark is being technical.

 

Someone told me that turbocharged cars need premium, so my first fill up was on premium. After joining this site, my 2nd fill up was 87 per a thread almost exactly like this, the car got peppier, and seemed less like it was going to die at any moment like it did on the premium.

 

100:1 or lower

 

Can I just use 89 on the T2? Or do I have to run 91-93?

 

i put half a bottle of octane booster in my tank and it was off the fu**ing hook! all over the road... hmm

 

Okay...

Octane has absolutely nothing to do with increasing HP, so you were imagining things if you think that octane booster helped a FC engine in anyway.

See the octane rating is a measure of the autoignition resistance of gasoline and other fuels used in spark-ignition internal combustion engines. It is a measure of anti-detonation of a gasoline or fuel.

Or in layman's terms:
The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites.

So extra octane in no way will give you extra power. In fact on a FC chances are that high octane levels will result in less power, as it takes more to burn.

The power output of an engine depends on the energy content of its fuel, and this bears no simple relationship to the octane rating. A common understanding that may apply in only limited circumstances amongst gasoline consumers is that adding a higher octane fuel to a vehicle's engine will increase its performance and/or lessen its fuel consumption; this is false under most conditions — while engines perform best when using fuel with the octane rating for which they were designed and any increase in performance by using a fuel with a higher octane rating is minimal or imaginary.

 

Fly on the wall says, "Very interesting discussion. I've got nothing add, but maybe I can learn."

 

So to make this clear for everyone:

Premix will necessarily noticeably decrease the octane rating of fuel when used in at least a 100:1 ratio, but the engine content of said fuel will not necessarily increase, thus the car will not be anymore powerful even though its fuel has a lower octane.

True or False?

 

so if you remove the OMP and premix do you have to add oil every time you put gas in the car? anyone care to explain premixing to me?

 

yes. that is the whole concept of pre-mixing.

 

so what would be the proper proportion for premixing? and doesnt that get a little expensive?

 

Not really...

I get the stuff in 16 oz. bottles at Wal-Mart for 1.39 a bottle. Not too shabby if you ask me.

I've always done 1 ounce of oil per 1 gallon of gas.

 

I'm glad somebody corrected that bit about jet engines and how kerosene (Jet A) works in them. However, I would be remiss if I didn't point out that a jet engine is not "external" combustion. the combustion in a typical turbine engine my be constant pressure and constant volume, but that doesn't make it external. An external combustion engine would be something like a HTD sterling engine. I agree with everything else you said and am glad you said it.

 

So....... does that mean I can use 89 on my car without worrying? (T2)

 

you can use 87 if it's a stock T2.

 

Oops, my bad. Thanks for the correction.

 

I guess next fill up, I'm knocking my car back down to 87....maybe that would explain why my car seems like it keeps getting slower and slower...hmm, probably in my head, but who knows

 

octane ratings are based upon the temperature at which the fuel ignites. as an engine compresses fuel it gains pressure and temperature. a knock occurs when the fuel ignites too soon because it reached its combution temperature BEFORE reaching the point of spark plug ignition. adding octane(as i'll call it) or detergents and additives to the fuel, effectively raises the temperature at which it combusts in order to prevent knocking. a rotary engine uses lower octane fuel because the temperatures and pressures in the engine before spark plug ignition are not high enough to ignite low octane fuel.

 

so from all this if im on E when i fill up i can put about 3/4 of 2 storke oil.....

 

well if the octane rating is lower wouldn't that mean the fuel ignites and burns more readily? would this be enough to increase the power even slightly?

 

The increase in power comes more from better sealing, effectively raising compression on a questionable engine.

But if the seals are tight, then it won't matter