[tim3058]

A question to those who paid more attention in chemistry classes than I did:

The 92-95 Civic Vtec-e engine uses a "lean-burn" mode during cruising, increasing the air/fuel ratio considerably, giving the car its considerable mpg. One of the drawbacks is a severe drop in power once the car is in lean-burn, generally limiting hill-climbing and restricting 65mph cruising to level-terrain (unless you step on it and kick the car out of lean-burn, and get 40mpg instead of 50). Elsewhere I recall reading lean-burn mixtures ignite and burn slowly, thus my question: Would 86 octane fuel promote lean-burn mixes more than 87, and 87 more than 91, etc?? (faster ignition, faster flame front, etc). I just started running 86 octane this tank (it's cheaper, plus the station that sells it discounts another 5 cents/gal if you pay with cash, so its like 40 miles extra each tank for free), so I don't have any of my own data yet (seat-of-the-pants doesn't notice a difference yet), was wondering if any of you already studied this or maybe know more from the chemical side. If there is a slight bump in power, then thats a bonus to the savings. If the consensus is that it would hurt mpg, then its an issue of lost mpg vs. savings at the pump. Thanks.