racing fuel compatible with M5 ? - The Unofficial BMW M5 Messageboard (m5board.com)

steve adams · 13th January 2002, 06:49

The neighborhood Citgo now has 100 octane racing fuel available ... it's a bit pricey (around $4 per gallon) ...

Is there any performance benefit to running 100 octane occasionally in the M5 ?

Is this high octane fuel compatible with the M5 ? Any drawbacks in terms of wear and tear on the engine?

Seems like the combination of the sport mode setting and 100 octane fuel would be a literal kick in the pants ....

Thanks,

Steve
'02 Titanium / Silverstone

KirklandM5 · 13th January 2002, 07:34

as long as its unleaded its ok...

only a dyno test would indicate any performance benefit...

Since the highest street octane in Europe is 93 using the US method of measurement (98 RON, 88 Motor or 93 AKI). I doubt if anything over say 94 would make a difference using the factory computer software.

JL

joegraz · 13th January 2002, 16:04

How 'bout with Dinan Stage II? Does anyone out there know?

wbarber · 13th January 2002, 18:05

This is an interesting question. I have been putting Sunoco 94 octane gas into my car, but I don't know if I am wasting my time. Any thoughts on this?

Teutonaddict · 13th January 2002, 18:29

And I recall reading that Steve Dinan said (at last year's M5 Extravaganza) that true race gas is the easiest way to extract more BHP from our beasts.

I use 100+ octane unleaded race gas on track days, and I swear the Beast pulls harder. Furthermore, there was a recent (12/01?)study done at Hot Rod magazine with dyno pulls at various octane levels (and with various so-called "booster" additives), that showed better performance with more true octane. The additives proved worthless for adding HP, however.

BTW, these were done with a pretty basic Chevy big block (if I recall correctly), without the benefit of our truly remarkable BMW DMEs (brains).

Bottom line: I use it when I can.

-Dave

Teutonaddict · 13th January 2002, 18:33

Hey Steve-

Where is that high-octane pump? I'm coming to Charlotte next weekend to visit my brother (around South Park Mall area), and would love to load up!?

Just curious. Thanks!

-Dave

KirklandM5 · 13th January 2002, 18:48

There have been 2 recent magazine tests on octane. Car & Driver did a test using modern cars and Hot Rod which did a test using a small block Mopar or Chevy (can't remember, but I think it was a Mopar).

Key Points From the C&D Test.

On cars designed for 87 octane (like Honda Accords), stepping up in octane made no appreciable gain in performance.

For cars designed for premium, STEPING DOWN in Octane DID cause the car to LOSE performance. But the computers kept the motors from detonating by retading timing.

Note that they DID NOT Test RACE unleaded in the modern cars...so it's inconclusive if it would make a difference. But if the cars designed for 87 did not pickup power with premium, it's highly unlikely you'd gain performance going over 93-94 in cars designed for premium.

Nor did they compare the various flavors of Unleaded Premium, which can vary from 91 to 94 depending on where you live. In addition they did not test the various formulations of gasoline which include MTBE, non-MTBE, CA reformulated etc.

Note that in California, the pump racing gas...from 76 is a reformulated blend as its approved for the street....so it may have the octane but not necessarity optimal burn rates for power in an engine that does not need it....See below..

Now in Hot Rod's test they had a 10:1 + compression motor for there test.

Using 87 the motor made something like 390ish hp,
Using 91 or 92 they picked up a few ponies, it was less than 10hp
Using 100 unleaded it picked up around 10-12 from the 87

The real surpsise was 110 LEADED which made more power than the 100, with LESS ignition timing. This led Hot Rod (and myself) that it's not just octane it's also the formulation of the fuel.

Even the 100 unleaded racing needs to be formulated as a "Street" emission friendly gas in california.

steve adams · 13th January 2002, 19:21

Dave -

Not sure if other Citgo stations in Charlotte may also have the 100 octane pump ...

... the one in our area is north of the city about 17 miles on I-77 , exit 28 (Lake Norman - Cornelius exit) .... take the exit, turn left on Hwy 73 and it is about 1/2 mile down the road on your left .... single pump in center island labeled "racing fuel" ...

... they may carry racing fuel since we are situated close to many NASCAR team shops in Mooresville .... those guys probably enjoy running the higher octane gas in tuned personal cars ...

I may try a tank to see if there is any notice-able performance enhancement ...

Steve
'02 Titanium / Silverstone

Bart Carter · 13th January 2002, 20:30

The only available octane in Las Vegas is 91.

I the altitude requires less, so they take advantage of it.

greg · 13th January 2002, 22:28

Best we can get here in CA is 91 octane, plus it is "oxygenated" between October 31 and anuary 1. I recently spoke to a BMW mechanic who told me that BOTH reduce power.

Based upon personal experience, there is ABSOLUTELY AND POSTIVELY a power increase if you get the octane back up to a reasonable level. Anyting over 96 or so is PROBABLY wasted, but I'm not sure. So you can save money by getting a half tank of 100 mixed with your usual premium stuff.

Do be sure it is unleaded though - not all race gas is.

Hey pilots - what about AVGAS? Is unleaded 100 available at private airports? does AVGAS have any additives that might be harmful to our engines?

PhilSeastrand · 13th January 2002, 22:45

Steve Dinan said at the Sears Point meet that 100 octane was good for 8-10 HP with the M5. Our software will advance the timing until it knocks, always, so it can take advantage of the high octane -- not all cars do this.