Any car will go a million miles if you throw enough parts and labor at it. The ususual life span for diesel Benzes with typical care and use seems to be in the 3-400,000 mile range. Some go longer, some take a dump sooner. It depends mostly on the way the vehicle has been maintained and used.

Any vehicle with over 300,000 miles on it is going to have problems crop up from time to time. Shop labor is expensive, so if you are paying someone else to work on your car, this can cost a lot. If you do most or all of the work yourself, these cars aren't terribly expensive to keep up.

When you say bio fuel, are you talking biodiesel or SVO/WVO? I have yet to hear of any diesel engine having a serious problem running on biodiesel. I've heard mixed stories about SVO/WVO.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 401,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 26,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.
99 Mazda Miata 183,xxx miles.