Take a look around at the diesels that get to very high mileages, they are not driven like they were stolen. The boy racers generally end up wrapped around a tree long before their motors are worn out.
My old 300d mainly did long trips, steady at about 65mph. It did 800k miles before I retired it. The motor was never pulled down in that time. In the mid 80's the diesel w123 was the most common taxi in the world, you dont see taxis driven like they are doing a lap at Daytona! The main thing for "cleaning the gunk out" is to make sure the motor runs for much of its life at the correct operating temp. A motor that is only used for short runs and so run cold for most of its life generally has a short life.

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Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving