With gas approaching $4 per gallon here, I decided at my last fill-up to try a 50/50 mix of regular and E85. This blend should more than satisfy the octane requirements of the 3.5 HO in my 300M (which will run okay on straight 87, but doesn't like it--89 is spec'd). So far, engine seems peppier, no starting problems, no check engine light. We'll see how things are after 2 or 3 tanks of this mix.