Yes, I've seen a strange correlation between the level of performance your TC gives you and how it affects gas mileage. The more fun it is to drive, the worse your gas mileage gets for some reason :smile:
No, he's correct, it doesn't affect mileage too much if you have a lockup converter. You might lose 10 miles to the tank if all of your mileage was city driving and your tranny can supply the pressure and volume to make your fluid coupling tight if your TC is efficient enough to begin with. Not meaning to be redundant, just having fun and then reaffirming you had the correct information.