I've complained before just how bad my TL hates the hot weather. Many others complain too. Engine is bone stock. My gas mileage has fallen to 13mpg with 100% city driving. It takes over half throttle just to stay next to traffic from a redlight. I even shut the AC off sometimes while accelerating to help it out. I've been over every possible cause and going by others' problems, it looks like some of these cars just have over aggressive timing in the heat. The 11.0 compression ratio doesn't help either. So a week ago, I mixed half 109 unleaded with half 91 (the highest available at the pump) out of sheer frustration. I reset the MID every time I fill up, it has always been extremely accurate and dead on 13mpg for the past month. I do the same drive day after day. At the end of the week and a tank of gas, mileage has gone to 19mpg, about what the EPA rating is. It now takes 1/4 throttle or less to accelerate normal and number of downshifts are reduced since it doesn't require as much throttle. Wide open power is much better. This mileage jump and power gain shows how bad this car is in the summer time. If it were tuned properly it should show 0 gain from this. I want to do another tank for a better average but at $75 it's too expensive. I guess there's no real point other than to vent. I should've bought an Accord with 10.0 compression and a few extra cubes to make up for it. To be fair, I believe the VP 109 has a faster burn rate than pump 91 but that's a minor part of it.