AFR's while cruising

[Chris86NA2T]

while cruising on the highway at a fairly constant speed, how lean do you guys go to get the best fuel economy? right now i stay at 14.7 + or - .3.. is it worth it to go a little leaner? i went to about 15.2 for a while with no problems. i have highway trip coming up this weekend and im gonna do one way at 14.7 and the other way a little leaner and calculate mileage at each setting. how about timing settings for fuel economy? any input? thanks a lot

[Jason84NA2T]

more timing and leaner mixture will give you better economy, but I would not go over 50 degrees of advance. You may recall I was getting over 30mpg highway with the 8.3:1 engine while leaning it out to 15.0 and running 50 degrees. This was without an O2 sensor feeding the ECU feedback. Some people say this is not "healthy" to do to an engine, but I see nothing wrong with it unless you go leaner than 15.4 or so, where temps will start to skyrocket.

[grahfz]

remember, 15.0 is only .3 off from stoi, so it's not overly lean. And given the 'easy' conditions of cruising where it only requires the engine to generate a few horsepower to maintain speed.... you can get away with quite a bit.