PinoyC250

Has anyone tried using 100% octane gas on c250? Am curious on the results.

dol4er

The results are wonderful I drive with 100 octane fuel only and it makes the engine work in a much better way, noticeably.

Petje

We have 95 and 98 , normally i put 95 in my car and now i have put 98 in it for a long trip.
No difference , only the price .

dol4er

There is a difference but not everyone can notice it. It is not like adding 50hp but there is a little effect. Btw, if you put a Brabus performance module, you will be required to refill with 98+ fuel only.

Glyn M Ruck

This is to be expected. The cars run a mild advance curve. Octane rating is a fuels resistance to knock ~ that's all. The only time one MIGHT feel any difference is if someone changes the advance curve and the knock sensor detects the onset of knock & the ECU retards the timing if you don't use high octane fuel.

Higher octane fuel allows one to run more advanced timing/higher CR.

Petje

Thanks Glyn!!

They say on 98 the car use less fuel , but also
Zero difference.

Glyn M Ruck

Fuel in Europe is very good stuff. You probably don't drive in a fashion that encourages knock. e.g. WOT at low RPM. If you don't run 98 there will be occasions that the ECU is retarding timing but as I've said Benz runs conservative advance curves. In China where fuel is poor these engines knock frequently.

As the engine gets older you might find it is more inclined to need 98 due to combustion chamber fouling & hot spots.

kevink2

Glyn, just for clarity, the pump gas in europe (and China?) is based on the RON number, which is about 4 points higher than the US AKI rating (RON + MON)/2 .

My experience is that if you run a gas that is several octain points higher than the advance curve requires, then your perfomance can be degraded. The energy available from high and low octane gas is about the same, but you need to run the maximum advance each fuel requires to get that full energy rating.

.

Glyn M Ruck

Yes ~ both are based on RON although in Europe there is usually slight octane giveaway whereas in China the fuel frequently does not meet the claims.

Regarding your other comment that can sometimes be correct depending on fuel blend. It's a matter of achieving complete combustion at the right time. With pump gas & moderate tune you won't really be able to measure any difference in my experience. Winter fuels in Europe have very little heavy end to them as well.

With 100 Octane racing fuel or 102 Aviation piston engine fuel the density is usually higher with more heavy end in the blend. Then it's desirable to have that slightly more advanced timing to complete the burn cycle. It's very fuel blend dependent rather than octane dependent as long as you have enough octane to prevent knock. In racing you are usually running as close to detonation as you can get away with. Of course in racing sometimes people overdo it with dire consequences. To be fair moreso with two stroke engines.