If you want to make pump gas into “racing gas” for engines with 11:1 or more compression, high-boost superchargers, big doses of nitrous or any engine run on a race track at sustained high-speed/high-load; forget it. No canned octane booster in any quantity will fail to stop detonation under those conditions.

If you “read” spark plugs to tune your engine, the redish-brown MMT residue makes useful readings impossible. Levels of MMT octane boosters just moderately beyond the recommendations of booster manufacturers will foul spark plugs, damage oxygen sensors (O2S) and plug catylitic converters. High percentages of MMT contaminates engine oil and leaves hard metallic deposits in the combustion chambers, piston tops and upper end of the cylinder walls such that engine wear is greatly accelerated. Do not use them in concentrations higher than suggested by their manufacturers.

That some automotive manufacturers believe MMT causes problems with the second generation on-board diagnostics (OBD 2) on ’96 or vehicles has us concerned about long-term use of MMT boosters in OBD2 engines. We would not use a MMT octane booster in a Corvette with OBD2. In fact, we’re not even comfortable with long-term, regular use in any engine with 02Ses and cats, OBD2 or otherwise.

While some of them have a short-term practical benefit, the economics of octane boosters aren’t much better than mixes of pump and racing gas. Factor in the durability issue and they might not be as good a value. We priced NOS Racing Formula on the Internet and at retail vendors. It averaged $12.99 per bottle. At time this article was posted on the Internet, 91-oct. was going for $2.59.9@gal. at local gas stations and we purchased "Rockett Brand 100" unleaded (106 RON, 96 MON, 100 R+M/2) for $4.75@gal. Sixteen gallons of 91 boosted to 94.5-oct. with a bottle of NOS ran $54.57. Sixteen gallons of 94.6 octane gas mixed 3:2, from 91 and Rockett 100 unleaded cost $55.35, seventy-eight cents more. Considering the two mixes differ in price by a little over 1%, the engine and emissions controls component damage you risk with MMT boosters seems to point at racing gasoline rather than octane booster as the sensible way to raise the octane of pump gas.