I would have no problem using a 240D, no matter where I wanted to go. just plan your time and trip accordingly. sure a 240 in no race horse, it`s only 67 hp, with a low geared differential. 3:69, auto or manual.
I usually drive ours around 60 - 65 on the hwy. and using a GPS, and with some intown and some freeway driving, one tank was 28.18. the next tank freeway and climbing over Hwy 50 (7500 ft) to Nevada, got 28.80. she poops out some at the higher altitudes, so down into 3rd gear.
I do have a 3:58 diff out of a Euro 230E, so gears it up 3%. type of driving I do, i can`t see going up any higher. there is one guy that put in a 3:07, but must live in a flat area, or always going down hill.
I have never driven a 300D, but they are 80hp and a 3:46 Diff.
the 300D turbos are 123 hp with a 3:07 Diff, except for the 85 with a 2:88.
our 85 with the 4-spd picked up a good additional 3 mpg. we get high 28 to 31 + mpg. but that is driving around 3000rpm`s. haven`t checked this one with the GPS yet to confirm my spedo and miles driven.
I guess the bottom line all depends how young you are, and your Testosterone level.
Charlie