The truck went from 18-19 mpg without, to 16-17 with the Edelbrock. Towing the boat, 9-10. On the boat, it's a single fuel injected 502. It's not as bad as I would've thought. Typically pull it out of the home lake 5-6 times a year and carry it to the Gulf Coast. Normally run in the intracoastal waterway approximately 5 days of the 7 and it makes it on a full 90 gallon tank. Plenty of little islands/sand bars in the intracoastal for the dog's to get out on without bothering anybody. Going from Destin to P.C., or Gulf Shores to Pensacola, that'll suck the bottom out of it. But I try and be reasonable on the boat and it's best cruise speed for mpg's is around 30-32mph. The bass boat on the other hand, I'm Wide Open!