Blownbenz

Will running 100 octain unleaded make any difference at all on a stock e55?

RenntechE55

I was low on gas one night at the track and I put in like 3 gallons and it didnt make any difference, you might need to use more to see a difference.........

TheDzadz

I use it in my Cls63 and I feel a difference but I also put alot in it, I do half 100 n half 91. Also it is 7.50 a gallon lol, well thats how much I pay

chiromikey

besides placebo affect, NO...at least not any significant difference until your car is tuned for it.

220S

Agree with Mikey. My experience (even filled the tank with it) is no difference (in an E63.)

But I did notice better mpg.

hooleyboy

I run only 100oct, I drive to work on 100oct, I got to the grocery store on 100oct. Infact I've got 109oct in my car right now. On the dyno 100oct is worth about 15-20hp by it self. The ECU will adapt to the 100oct and add some timing and increase power.

100oct or race fuel, burns slower or longer than standard pump gas. It creating more energy on the piston because it burns longer through the down stroke. Rather than a quick poof like standard pump gas.

Octane rating is basically the fuels ability to resist detonation. So more timing can be added simply due to the fact that race gas will resist prematurely igniting under compression.

Cars with very aggressive tunes or very high compression ratios require higher octane fuels. If I was to put 91 octane in my car it would blow up with the tune I'm running right now from detonation.

With an AMG Mercedes already set to run on higher octane pump gas, like 91-93oct. Adding or running 100oct fuel will cause the ECU to make an adjustment. The end result will be more power in our cars.

That doesnt mean go out in toss 100oct in your minivan or in your stock Honda Civic. That could have some adverse effect on the car and would just end up wasting money on $8 a gal gas. In fact they may not even be able to burn all the race gas and you will end up with fuel in areas of your car you dont want it.

EDIT: I would also like to add, With countless dyno pulls, and witness to countless more. 100oct (mix of 91 and 109) acted like a tune in a bottle. consistently showing more dyno WHP than over standard 91oct fuel.

TheDzadz

I actually waste more gas. Thats weird

220S

My understanding (at least with later model E63s) is that the ECU is set at either higher octane (Euro), 91-93 (US), or on 'auto' where the ECU will eventually adjust to the octane you feed it. But that in the US it's set by default to 91-93 and so 100 won't do much. So you have to have set it to 'auto.'

Maybe that's all bs, but I got that info from somewhere(?) Maybe on the PL?

hooleyboy

Its my understanding the 63's have strange things going on when it comes to fuel. So on the 63's I just dont know??

Marcus Frost

I dyno'd my '03 E55 when it was stock on 100 octane and 93 octane back to back. 100 octane lost a bit of power on the dyno.

It's important to know that you want to run the least amount of octane possible without causing pre-ignition or detonation. Running too much octane can rob you of power and generally make your car run poorly. People tend to think that high octane is like injecting nitrous into your engine but that's really not the case.

-m

chiromikey

+1

even with all my mods, i saw no real gains on the dyno with higher octane fuel until the tune was changed.

Hammer Down

You have to run 100/91 octane mix to get the best out of your 55. Whoever wants to doubt me check my sig!

220S

Yeah, that's what I end up doing sometimes. But only because the gas in CA is so low octane and crappy to begin with.

chiromikey

mixing our crappy 91 (at best) up to 93 has always given me the best results at the track.

MRAMG1

Exactly my friend.

My ex crew chief worked at a local refinery/research plant. And botom line is ALL engines require a finite amount of octane, running more or less only hurts performance.

smokinmb

Absolutely you’ll see a performance increase when using 100-octane fuel. I’ve had great luck using VP’s StreetBlaze100 in my e-class. The car is more responsive, quicker, and I definitely have a lot more power and torque.

MRAMG1

And you base this on:

1. Dyno knowledge
2. Research as an engineer in octane developement at the Gulf resarech lab in Cheswick PA 1985-88
3. MB ECU tech with knowledge of their parameters
4. Seat of the pants feeling

I have the first two, or first hand knowledge of, in this playing field, your's are?

blackbenzz

Don't you have #4 too? I wash my car and it feels faster to me lol. The scientific explanation is that when its clean it has less dirt and dust on it and the wax allows for better aerodynamics. I'm not a physicist but I stayed at a holiday inn express last night... oh wait... no I didnt, doh!

SLK55R

If your car isn't tuned for 100octane ... its a crap shoot. You might get a bit better performance or you might actually lose some performance.

I'm like Hooley I run 100octane straight all the time. But my car has been tuned specifically for 100octane.

IF you are running 100 octane or any race fuel ... make sure that you also are adding techron etc.

str8ridin

I know, what's up with that?!



So, all you octane gurus - what IS the highest octane allowed for a stock E55 before it starts to lose power? 93? 94? 95?

rarfinancial

Does the knock sensor have anything to do with GAS?

MRAMG1

That's a keeper my friend

PS; Washing a car is good for atleast 10rwhp

MRAMG1

There really is NO clear answer on this one as EVERY engine will have slight differences. As Marcus F said, and is dead on, use what ever grade you need to suppress detonation, NO MORE.

Variables in engines are, timing, build up on valves and pistons, assembly tolerances, etc, etc.

One engine may run just fine on 91, while another may require 95.

Bottom line is, unless your ECU is tuned for 100+ octane save your money

blackbenzz

I have a few of these too

MRAMG1

The TRUELY sad part is, you could probably get someone to bite on that at the track

Or in our favorite section around here