/6...318...or 360???

danmc77 said
If it's a daily driver, park it and buy a Honda if you're worried about gas milage. I don't care what engine you have, if you have a heavy (by comparison to modern compacts and such) old car with old technology - you're NEVER going to get good gas milage. Sure, the \6 gets better milage than it's 8cly cousins, but not compared to late-model compacts and mid-size cars. Sorry, but if that's your primary concern, I would say don't make it your every day driver. If you insist on using it that way, there's no debate - use the \6 and get better milage than the V8s.

I dunno, it seems like modern cars are heavier than old ones. At least similarly sized. I bet if you compared an old Dart or Valiant to a modern mid-size car, the modern one would be a couple hundred pounds heavier. I say if you want mileage, get a slant-6, a factory Jeep straight-6 EFI setup (or not, might be a bit tough to adapt, I don't know), and a turbo from the 80's turbo-4 cars. It would have a good amount of power and the mileage would hardly be any worse than an NA slant-6.