I have been driving it a lot and it always falls right in range with previous postings. Tennessee has started putting %10 ethenol in all the gas but it didn't seem to make any differance. As a matter of fact I topped it off with 5 gallons of E-85 the other day to fill the tank, didn't seem to affect the way it drives any I will post how it affects the MPG when I finish off that tank. It was about 50 cents cheaper than 93 octane and Tn does not subsidize it. I would not be afraid to run another point or 2 compression with it to bring back some of the suposed eficiency loss

I would recomend the 273 over the slant because the only custom thing you need is pistons. With the slant you need a ton of milling to get closed chambers and zero deck. If you did all that milling I bet you would still need a custom piston to get valve clearance and low enough compression unless you want to make it run on e-85. If you could go this way though I bet a 170 would get better mpg on e-85 than a 273 on 93 octane. However if you threw an a-500 behind the 273 it might be close. I do beleive based on what I have learned: a 273 built with custom pistons and custom cam and a performer intake and OD that 35 mpg is reasonable. Also if I was running a motor that small that slow I would get some smaller headers like 1-5/8 and mabey add in an extra 12 inches to the primaries to boost low rpm tq. A narrower wheel would probably be good also, mine are 7.5 wide but have a very low profile tire to lower rolling resistance.

If I built it for e-85 I would open the heat crosover to gain some bit of efficency that it suposedly loses. It burns cooler so it should still not ping. Mine is blocked and I think it would knock if I opened it.

I mention all the e-85 stuff because I am thinking of switching it over with thinner head gaskets and some head milling.