What I found to be real bad is warming up the engine for a minute in the morning before I take off. I did that a few times and got 3 mpg less on that gas filling.

Oh, and the stop-light racing might have contributed too, against an old Mustang GT; just couldn't resist, since I come from an American muscle car myself.

I don't do the warm-up in idle routine anymore - instead I try to keep the RPMs under 4000 for the first couple of minutes. Seems to help.

-Peter

 

Here's another interesting ongoing thread from the tech forum: Syntrix's A/F Graph Thread

He's found that @ idle, the fuel map runs pretty lean, but get on the throttle, and she runs very rich... Lean-running @ idle is expected to bring the cats up to operating temperatures faster to pass emmissions tests. Richer fuel maps prevent higher temps from cooking the cats faster over a period of several years -- at the expense of fuel economy and power. These are only preliminary findings, mind you, but they would explain a lot...