Re: Gas mileage decrease when....
Quote: "Most vehicles get less mpg's in the colder months, even my motorcycles."
I do not know where you found this myth, but some factors may contribute to how you came up with this hypothesis. I'll come back to this later.
I didn't come up with a myth, just years of driving in a part of the country that has 4 distinct seasons plus I have kept up with gas mileage on a spreadsheet for the last 15 years. Some of my vehicles do better than others but all drop 5 to 20 percent. My tacoma was the worst, 22 mpg in summer and 18 in winter driving the same routes. My chevy truck usually just loses 2 mpg, my suzuki motorcycle loses 5 and my victory so far has lost 5 mpg's since colder weather and winter blend of gas. The cherokee seems to be doing alright, avg mpg was 23.7 but has dropped to around 22.2 on the last two fill ups.