I'm really enjoying my 240D, not so much because it's a diesel, but because it has the typical Mercedes attributes of good ride comfort and handling, and it's one of the last simple, durable models Mercedes sold in the US. If Mercedes had sold a one of their small-engined gas 123 with a 5-speed in the US, perhaps a 200 model, I think one of those might have made my wish-list.
As it is the 240D isn't the most economical car I could have bought. An '80s 190D would certainly do better, but those don't have the 123's reputation for durability. Or I could have bought a late-model 5-speed Corolla, but it's not a Mercedes and would have cost far more than my 240D, even factoring in my fix-up costs.
At least my 240D's 22-24 mpg city mileage is nearly double the mileage that any of my gas Mercedes (except for the Ponton 180) ever achieved in local driving, and a couple mpg better than my Nissan gets in traffic. So, unlike most of the gas Benzes I've had, the diesel is practical enough to take over as my alternative local daily-driver.
However, with it's overdrive gearing and relatively quiet ride, the Nissan will continue as my long-distance transport, as it does manage over 30 mpg on the highway.

As for alternative power, if you get the chance, you should check out some of the massive marine steam engines still open to the public, such as the huge triple-expansion reciprocating engines on the liberty-ships Jeremiah O'brien in California and John Brown in Baltimore, Maryland, or the two remaining intact walking-beam side-paddlewheel engines on the Ferry Eureka in San Francisco, or the Lake Champlain passenger steamer Ticonderoga, on display at Shelburne, Vermont.
Both liberty-ships are still (the last time I heard) in operating condition. Twice a year, the John Brown has been taking the public on day cruises out of Baltimore. Small groups can visit the engine room during the cruise, and watch the 3-story tall 3-cylinder engine develop 2000 horsepower at 70 rpm. The exposed piston-rods, connecting-rods and massive crankshaft in motion, make for an awesome and unforgettable sight!

Happy Motoring, Mark

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DrDKW