Welcome Red. I'm sure you're glad you have a 4x4 vehicle now that winter is here (unless of course you never get snow).
I was VERY close to buying a 1994 Jeep Grand Cherokee with the 4.0L engine mated to a Quadra Trac system (full time 4x4 only) this past summer. It had its own instantanious MPG readout device and I was impressed that it was showing 28-30mpg (22-25 miles per US gallon) when I drove it at 55mph on the highway.
However, the Jeep Grand Cherokee has a Cd of 0.44 which is very good for a 4x4 vehicle.
What kinds of aerodynamic modifications do you have in mind?
Snow is more recreational here in the Bay Area. Rain is more common, but with the way weather trends have been going, snow could be possible.
ZJ (Grand Cherokees) are pretty good 4x4s, aerodynamically much better than the Wrangler, hence is higher gas milage. 4.0l is capable of 30 mpg (when drafting a semi linky, and so long as the clutch in the transfer case doesn't wear out the 242 transfer case is a good system.
Mod wise, I need to do some airflow tests to see how exactly air is flowing over the jeep, but off the bat I'm thinking some kind of hood mounted deflector, and perhaps AirTab like devices on the end of the hard top, ending with smoothing out the belly.
Closest thing I have to a "Wind Tunnel" test is this. Gets the basic idea across though.
thanks cfg83, just been waiting for this semester to end before working on anything. I'm thinking that something along those lines should work out fairly well, logically speaking. The Jeep has next to no curves on any portion of the body or the hard top, from the doors back its pretty much shaped like a semi -trailer. I think 7-10% gains would be lovely, though I don't know how realistic that is