Some random observations...
Our CRD gave us great mileage on some mostly-highway trips (26-27mph). It's only got 2000 miles on the clock so far. That is pretty impressive.
On around-town driving with winter diesel, we just clocked a tank at 16.5mpg. This is mostly running errands around town. That's not as high as I'd like, although I recognize that the CRD is a heavy vehicle and the diesel has a higher fuel penalty for short trips than the gasoline engine does (warm-up A/F mixture, viscous heater). Given the same driving pattern, I think the gasser would be doing better right now.
I've read Tightwadsjeeper's posts about improving fuel economy through driving technique, and he is spot-on with all his recommendations. Over the past 15 years, I've developed a driving style which pretty much mirrors his, and I tend to get better mileage than average on every vehicle I drive. It's just common-sense stuff about maintaining momentum, minimizing braking, and maximizing drivetrain efficiency. I think he is just defending the 3.7L's ability to get reasonable mileage when driven with that intent in mind. I bet he'd work wonders with a 6-speed CRD too.
While I think the 3.7L would be nicer right now in some respects (better short-trip economy, no cool-down waits), I would still choose a CRD if I had to make the choice again. If it were primarily a city commuter vehicle with the occasional weekend trip thrown in, the decision would be a little more difficult. It seems like if you can squeeze some highway driving in with the CRD, you'll get some good mileage on that tank. If not, then the numbers I've been seeing are more comparable with the 3.7L numbers I've seen - again, only with 2000 miles on the odometer right now.
Oh yeah, and the KJ is an AWESOME city vehicle. The visibility is excellent, and I can swing 135 degrees around into an angled parking spot on the other side of a narrow city street!
- Chris