- This is a welcome sight: gas prices are falling and are down to less than $2.50 per gallon. According to AAA, gas prices across Michigan went down by about $0.11 in the past week. On average, we're paying about $2.45 per gallon, which is about $0.19 cheaper than it was at this point last year. In Detroit, prices on average hover around $2.49, down $0.8 cents. If you're looking for the cheapest gas in the state, it can be found in Flint where prices average $2.34 per gallon.