Not bad for a 10 year old 6 cylinder car

I pulled into work one day last week and a patient pulled in next to me. Who then commented on how my car must guzzle gas being a 6 cylinder. He thought I was nuts and wasting money. I knew my mileage was decent and he agreed that the car looks to be in extremely good condition, which it is. So with my last gas purchase I made a mental note of how many gallons. My 10 year old, 6 cylinder Pontiac gets 24miles to the gallon. I think thats excellent. My original estimate was 18-20 miles per gallon, lol.