Fuel trims and cold weather question

[gtman]

I've been running the TSP Stage 1 for a while and my fuel trims were consistently slightly rich (-3 to -4 LTFT). But I haven't done a datalog in a while and these were done in warmer ambient temps.

Today, I re-uploaded the TSP tune after returning it to stock for a dealer visit. Datalogging, I noticed my LTFT was at +3. Ambient temps were just below freezing. Is it running slightly lean due to the cold weather or winter gas blend or a combination of the two?

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[fenix-silver]

Probably a combination of the two. My LTFT has been hovering right around 0 after hovering around -5 during the hottest part of the summer. Colder/denser air in conjunction with less volatile winter blend gas results in more fuel being needed. Obviously the ECU accounts for much of that, but no map parameters perfectly account for all the variables. A positive LTFT doesn't mean the car is running lean. It means the ECU is adding fuel to prevent the engine from running lean like it would be if it were injecting the amount of gas as when the LTFT was at 0. +3 is perfectly fine. I'd only really start to look into things if I were nearing +/- 10.