Is it true that our cars run richer when the weather is colder? Well before cold weather and my old tune i was getting like 260 per tank, and now im getting the most 220 with cams and a new tune, by different tuners. Before i go back to my old tuner should i wait till it warms up to see the difference between mpg?

 

It's the Gasoline.

 

thats seems about right to me....i have an 8, but mods are almost the same. i get about 240 give or take each tank with normal driving

 

are you guys at 10% ethanol gas all year (like we are in Houston), or do you still have winter blends? When we switched to 10% ethanol gas, I lost about 10% in mileage.

The rest is probably due to the cooler weather, but not necessarily you running richer. Cooler weather = more power = more gas useage.

 

What he said. You could be running richer because you are in different load cells in your fuel map due to the cold weather.

 

The only time I can see somebody running richer in colder weather would be during warm up, because it will take a little longer to get the car to operating temps

 

I've seen AFR's go richer in warmer weather as the previous posters said changes in gas and warm up as well as different traffic patterns lower MPG's.