Just noticed now that it has become colder in MI, that My gas milage measurement on the IP has gone down from 19.1 to 17.2. I have been driving the same in the same area getting costco gas at same station. Does anyone think the drop is due to the temp change/winter gas change?
Takes more calories/BTU to bring a very cold engine up to operating temp. Same goes for incoming air, too cool and it affects burn capability (not to be confused with compressibility and capacity). Generally, the colder it gets, the more fuel burned.
Happens on every car, with every brand of gas, every winter. After September 15, gas has 10% butane added, which lowers the BTU content. The colder it gets, the more fuel is used to bring the engine/transmission up to operating temperature. Lower MPG.