Car & Driver has a good article about using lower octane fuel.

 

Thats o.k. I keep paying the extra $2.50-$3.50 per tankful for Premium.

 

Im curious to know why Car and Driver did not compare fuel efficiency of cars being run on sub-par octane.

My understanding is that retarding the timing causes the engine to run richer and therefore would decrease fuel efficiency, possibly negating the money saved buying cheap gas. . . . . .

 

Knock sensors do not detect low octane, they detect detonation. As long as there is no detonation, the engine mapping remains as set and designed. Most if not ALL engines sold in this country can safely use low (to a point) octane....possibly as low as 85 R+M/2. For higher octane fuels to be fully utilized, it requires intervention by a human with the mapping or timing of the engine past the designed parameters.

Like I have said before.....the benefit of using Premium are less risk of detonation and when buying branded fuels, the level and quality of the performance and environmental additives used.

 

I think in a performance car I would just stick to premium gas. I want to keep my MINI for a very long time and anything to help keep the engine happy and healthy would be a good investment. My Honda can get the regular unleaded.