Swamp_Fox

Sometimes it is difficult to find the good gas specified for the M275 engine. One idea I had was using AVGas 100LL that is available close to me and wanted your opinions and thoughts on using this in the car. The gas has low lead but does have a bit.. The AVGas 100LL contains tetraethyllead to help prevent engine knock, however, from my understanding can be damaging to platinum in catalytic converters. Thoughts? Opinions?

herpderp

Lead damages cats and fouls o2 sensors. You'll do more harm than good long term running this fuel.

There's always boostane, or toluene. 50/50 Water/Methanol injection is a great solution as you really only need the added octane when you are under high load.

You could also tune it to reduce the amount of boost/ignition timing the car runs if you want that extra level of protection, but the ECU itself should be pretty good about pulling timing if you get a bad tank of gas.

Might even be able to import a barrel of ~100 octane fuel from a neighbouring state or something (ideally without ethanol) and just keep it on hand, and cut your tank of bad gas with it to bring the octane back up to an acceptable level. You don't want ethanol in the fuel because the ethanol will absorb water over time, and makes it unsuitable to store long term.

Swamp_Fox

Thanks for the information. If MB calls for 93 octane, what is the highest octane (normal automotive gas) that could be run in the car with everything stock that would not cause damage? What about 110 octane racing fuel?

herpderp

Well 91. If you can get a consistent flavour of 91 you should be fine. I don't know the finer details of the mercedes ECU, but it *should* have some sort of learned timing parameter, and if you consistently feed it 91 octane gas, it should learn to retard the timing slightly, or not advance it so much.

You should be fine so long as you don't notice any misfires, pinging, or hesitation.

An amount of boostane at every fill up wouldn't hurt you if you are concerned. Cheap insurance.

If your 110 is lead and ethanol free, You could mix the cheaper 91 at the pump with your 110, and get a nice blend of ~94 ideally. maybe even 95.

Swamp_Fox

I do not know what it means or how it would relate to the M275 engine but years ago I put 98 octane in my M3 once with the S65 engine and it ran better than ever with more power.

KyKen

AVgas is It’s not worth it. You will have to replace cats and sensors $$$.

Get a good unleaded octane booster with MMT. No harm to engine or environment if you use according to the directions. Cheaper than Avgas and great results.