Work truck - '97 Dodge Ram Cummins turbo diesel quad cab 4x4 dually. Many performance modifications. ~18mpg w/ standard load of tools, ~10mpg hauling a 15k lb trailer, ~21mpg completely empty(no tools etc.)
Toy truck - '91 S10 pickup, awd xfer case, quad cab, supercharged 6.2l diesel swapped in. Would have been easier to put an S10 body on a 1 ton chassis instead of putting a 1 ton drivetrain under an S10, but I've never been known to do things the easy way. Ask my wife. This truck is crazy fun; I wonder how long until the 6.2l blows up. No clue what mileage, I don't even keep track. If I put a brick behind the go pedal instead of on top of it then probably 25 or so.
Toy car 1 - '94 Mr2 Turbo
Toy car 2 - '06 WRX STi
In a drastic change from my SOP, both these cars are stock. They only get driven once every couple of months or so; the STi has ~5k miles on it. Not much clue on the mileage on either now, when I drive them it's for fun and I drive by the boost gauge. When I drove them more often it was 20-24mpg.
Wife's truck - '91 S10 Blazer w/ a Cummins 4bt swapped in, drivetrain and suspension modded to handle the weight. Some of you may remember me asking about diesel VW's, this is what we wound up with. Turned up the pump a bit but stock otherwise. My wife reports ~30mpg with a light foot on the throttle. I never did learn that trick.
All the diesels get biodiesel if at all possible. Working on a two tank heated system for my wife's rig so she can run WVO, SVO, or WMO. Will probably add a heater and heated fuel line to one of my Dodge's tanks as well.
I used to drive my cars often, but now I drive my fuel guzzling diesels even when I only need to move myself, precisely because they're run on biodiesel. The money stays in this country. My cars are rare treats.