Hello, I'm sure there are tons of forums on this but have not been able to find any good responses or fixes. About a month ago I changed the back tires from good year assurance tires to Hankook st 88t tires, the mileage did not decrease until about a week ago I had the front 2 assurances replaced with another set of 2 hankook st 88t tires. Since then I've seen a pretty bad drop in my MPG, it is winter but I live in socal so the temps dont go lower than 50 until late at night/early morning. I change my oil regularly (synthetic) just put a new air filter, had the Hybrid battery changed with a 5 year warranty. The tires seem to be the culprit, would breaking these tires in cause my mpg to drop so significantly, I was getting over 400 miles per tank and now I'm getting 340 to 350... Posted via the PriusChat mobile app.