This is a 1991 Honda Civic wagon. I think I've pretty much gotten as far as I can on driving technique. My best tank so far is 54 MPG. Mid to high 40s if I drive a little faster. Mostly rural highway driving. EPA highway is 32 new numbers or 35 old. I was getting 38 MPG without trying. I can probably hit 60 MPG, but a fellow motorist would probably shoot me before I burned the whole tank. I'd like to stay above 50 MPG and be able to stay close to the posted speed limit, which is usually 55 MPH. So I guess I'm looking for another 2-5 MPG. Possible?
Obviously I need to improve the car. I'd love to find a CRX HF 5th gear, should be good for about a 250 RPM drop in top gear. Should I add rear wheel skirts? Side skirts? Kammback? I'm not adding a full boat tail or belly pan. And I can't really lower the car or it will scrape on speedbumps and get stuck in snow. I currently have no outside mirrors, but I might add a small one on the driver's side since it's required.
Current (all untested) mods:
partial grill block (fan only comes on in low-speed traffic)
oversize front tires
increased tire pressure (slightly over sidewall max)
tires are mostly bald
hubcaps
air dam
no mud flaps