I purchased a used 2008 Civic. Now at 37,000 miles I had the tires replaced. I'm sure these were not the original tires, but I bought it from a dealer that does that sort of thing. Anyway, the day the tires were replaced my mileage went from 40 on the Hwy to barely 30 on the Hwy. Why is this? Not cheap tires, and they were to proper size according to the Civic Manual. Any suggestions would be appreciated.
I upgraded from stock 15" all-season tires to 225/40ZR-18 summer tires all around. Mileage dropped substantially.
I re-balanced the tires, completed alignment, and my mileage per tank jumped from 400km to 550km per tank.
Check if your wheels are correctly balanced.