[sjgrimsley]

Originally Posted by oil pan 4

The thing is the last body style of hyundai sonata the v6 has very simular weight, frontal square footage and Cd as a 3rd gen. The hyunda gets up to 8mpg better than the old V8 80s car.
So its possible for car of that mass and aero profile to get mpgs in the high 20s. The difference is all engine, engine management and gearing.

Engine management is already taken care of (2003 Corvette PCM, fully sequential EFI, distributorless individual coil-near-plug ignition, months of fine tuning with HPTuners). The engine is about as low-friction as it can get (it will be getting a roller cam soon to replace the flat-tappet). Only thing left is gearing. I see a 400 small block having no problem moving a 3200 lb. car with 2.56:1 gearing.

I have been wondering if the headers are skewing the O2 sensor reading. They are heated sensors but the header tubes let out a ton of exhaust heat. I wonder if wrapping them would have a positive effect? It's a common problem with long tube headers, where the O2 sensors don't get hot enough and cause a car to run pig rich. These are shorty headers, but with as mild a cam as it has, the EGT isn't going to be high at all.