Snake oil or the real stuff?

Peter Coomaraswamy

Peter Coomaraswamy

Well-Known Member
Site Donor $$
Messages
3,800
Reaction score
915
Location
Austin, TX
Has anyone tried this:
1580155151770.png
My new-to-me M5 (e39) calls for 98 octane. This was personally recommended by a local dyno /speed shop.
 
Peter, as a college student, Chem Engineer I often looked at the CRC (Chemical Rubber Company) handbook. Just a list of chemicals and their properties. Some hydrocarbons had their octane numbers listed and some were well past 200 octane, so I guess it can be real. Check and see what is in it. I tried like hell to get that 200 octane hydrocarbon for my "1971 Sexy European Mercury Capri" but I thought, it would probably turn to ashes so backed off.

BTW: Enjoy the M5!
 
Peter Coomaraswamy said:
Discretion is the better half of..... the survival instinct :cool: (something I didn't always follow)
Click to expand...
Peter, Consumer Reports used to test these. Like, bolt this on or pour this in the tank and get 71 mpg or a 50 hp boost. I would look for country of origin. But that's probably a fib too.
 
Actually, cannot believe you are actually considering such a product. The M5 is what, 20 years old? Survived this long, what do you expect to gain? Is there an issue, has it lived in some environment where it was only ever fed 98 octane and there is concern for the drop off? You most likely got this at a very reasonable price so why not just fill with the best/highest octane available in your area, and just focus on something else that could be improved. Just my opinion Peter. Best of luck! Mike
 
bluecoupe30! said:
Actually, cannot believe you are actually considering such a product. The M5 is what, 20 years old? Survived this long, what do you expect to gain? Is there an issue, has it lived in some environment where it was only ever fed 98 octane and there is concern for the drop off? You most likely got this at a very reasonable price so why not just fill with the best/highest octane available in your area, and just focus on something else that could be improved. Just my opinion Peter. Best of luck! Mike
Click to expand...
I agree, this car never had 98 octane gas in the US. The highest pump gas I remember or have ever heard of was 96 and that was Sunoco. Currently 93 or 94 is the highest available.
Octane booster additives do work. Just do your research and get a good one if you feel you have to have that.
The ECU in a E39 M5 has the ability to adjust the timing to compensate for octane by using a knock sensor attached to the block to prevent pre-detonation knocking.
 
Well ok then- I guess the answer is "no- don't do it" I was just curious, it was recommended- generally -by a dyno shop who is doing some tuning on my Shelby, but it was probably only in a racing context, we talked about a lot of stuff and in reading the owners manual for the M5 98 octane was recommended so I was curious to see if there was any collective experience on the board. I guess I have my answer.

Thanks Chris for the link- that's pretty cool but a bit of a hassle shipping and storing and pouring and spilling :-/
 
Peter Coomaraswamy said:
Well ok then- I guess the answer is "no- don't do it" I was just curious, it was recommended- generally -by a dyno shop who is doing some tuning on my Shelby, but it was probably only in a racing context, we talked about a lot of stuff and in reading the owners manual for the M5 98 octane was recommended so I was curious to see if there was any collective experience on the board. I guess I have my answer.

Thanks Chris for the link- that's pretty cool but a bit of a hassle shipping and storing and pouring and spilling :-/
Click to expand...

Yes, that is why I didn't do it.

The station near Dulles has one of their high octane fuels at the pump. You might check into whether any of the Sunoco stations on that web site offer this in Austin.
 
There's a couple gas stations in the bay area that have 100 at the pump... That link might help. It ain't cheap. 10 bucks a gallon but if it's only a weekend car it might be worth it...
 
Peter,

The higher the octane of the gasoline, the slower it is to ignite. Thus, high octane is used in high compression engines to slow the combustion rate and keep the gas/air mixture from exploding too soon before the piston gets to top dead center. The 'early' explosion with lower octane gas producess a 'ping or knock' as the piston tries to move against the exploding charge. This, of course damages the piston and connecting rod bushings/bearings.

SO - raising the octane of a 91 octane fuel is a way of making it burn slower. There have been many octane 'boosters' around since at least the mid-50's when I first started driving/owning cars. I don't know anything about this specific one.

Find an 'old' BMW mechanic at the dealership and ask him what octane is best to run in that engine. Don't ask a young guy, he only works on replacing electrical components in the cars!! - ha.

Cheers and happy driving.

Gary
 
Last edited:
I have always bought my race gas at ERC in San Lorenzo - they have 110 octane. Remember to bring a race can, they cannot pump directly into vehicles. We ran 22 pounds of boost with that in my 745i turbo.
 
Late to the party, but how well does the M5 run on locally available gas? If you don't get detonation, or lose power from retarded timing, there's no need to up the octane. I think many of these product, on street cars anyway, are snake oil.

Also, second the comment that the euro 92 octane requirement needs to be reinterpreted to the USA (R+M)/2 rating system.

Also, beware "aviation fuel" with high octane ratings (even if you can somehow get it) as they may contain additives pernicious to your street car.
 
Awesome folks thank you! Even though I'm sure I'm not the first to ask this question it probably does not hurt to revisit occasionally as one day there may be a product out there that would benefit us all. And charlie, good point in that I do not have detonation and there's allot of get up n' go in her so 93 it is :cool:
 
This is the key to that high compression motor running on just about any octane fuel. It would probably run on 91 just don't expect it to have the power.

The ECU in a E39 M5 has the ability to adjust the timing to compensate for octane by using a knock sensor attached to the block to prevent pre-detonation knocking which would be caused by lower octane fuel.

Gary Beck
 
tferrer said:
There's a couple gas stations in the bay area that have 100 at the pump... That link might help. It ain't cheap. 10 bucks a gallon but if it's only a weekend car it might be worth it...
Click to expand...

Agree, King's Union 76 Station in Redwood City has 100 Octane race fuel. I blend 6 gallons of 100 Octane race fuel with 9 gallons of 91 Octane fuel to get a ~95 Octane blend for my 71 Daytona. Heres the calculation: ( [ % Fuel A ] x [ Octane of Fuel A ] ) + ( [ % Fuel B ] x [ Octane of Fuel B ] ) = Octane of Mixture

Not sure the 3.0 would benefit from the same blend. Any thoughts on that?

975 Woodside Rd
Redwood City, CA 94061

Race Fuel 100 Octane.jpg
 
73Polaris said:
Agree, King's Union 76 Station in Redwood City has 100 Octane race fuel. I blend 6 gallons of 100 Octane race fuel with 9 gallons of 91 Octane fuel to get a ~95 Octane blend for my 71 Daytona. Heres the calculation: ( [ % Fuel A ] x [ Octane of Fuel A ] ) + ( [ % Fuel B ] x [ Octane of Fuel B ] ) = Octane of Mixture

Not sure the 3.0 would benefit from the same blend. Any thoughts on that?

975 Woodside Rd
Redwood City, CA 94061

View attachment 85461
Click to expand...

For a 71 Daytona, I'd hit Sears and put the good stuff in... Leaded 112. ;-)
 
You must log in or register to reply here.
Back
Top