The 85 runs fine. The 84 has a slight shake at idle but starts easily. The valves are adjusted the valves, Greazzer reworked the injectors and it has a new damper bolt installed and adjusted. I haven't done a compression check on either engine but the loosened oil cap barely moves.

I went to synthetic because both start soooo much quicker in the winter and I'm becoming lazy wanting to wrench less including oil changes. Blackstone said the Cummins can run longer between oil changes. I've decided to sample the SDs & see what Blackstone says. The 85 has ~ 250,000 on the engine and the 84 ~184,000 showing.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

mine has started at zero on 15w40 rotella,I change twice a year less than 2000 miles a year.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

One would think that more use equals more soot loading. If that is the case driving only on the weekends would equal less soot loading per time period.

An Oil Analysis would show the soot level and tell you if that is a problem.

It is a fact that private parties and money making trucks are saving money by extending Oil Changes while using synthetic Oil. You initially need to use Oil Analysis to determine how much use you can get from your Oil.
Of course in industry the Oil Analysis is also used to find evidence of pending mechanical or coolant leak issues.

I agree with the extra filtration and that I why I have a bypss Oil filter on my Mercedes.

In short an Oil Analayais could tell him how much use he can get out of the Oil and then having some actual facts the owner could make a decision.

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84 300D, 82 Volvo 244Gl Diesel

I change the oil in mine each spring when I bring the car out of hibernation. The past 2-3 years I haven't put more than a total of 2000 miles on the car.

I agree with using synthetic. It will be just fine sitting idle (no degradation). Running is better than sitting idle. The condensation (water) in the oil is a problem. Short, cold (engine temp) drives murder an engine. I worked at Amoco Research labs the year they did the 10W-40 in Buick odd fire V-6 trials (late 70's). They called it the 'old lady test'. They drove a dozen or so Buicks (Regals, I think) for very short trips (a mile or two) then parked the cars for a a few hours, rinse & repeat. They ran them for about a year, drained the oil, tore down the engines & inspected same. Then the worst bits were put on display. The remaining engines were re-assembled, installed in the cars, and the cars were auctioned off. The oil was a lumpy, runny, tar like sludge. The badly worn bits included cams, mains, piston skirts, and wrist pins. One or two oil pumps seized on the sludge. This was with dino oil, 10W-40 (SD I think). Same oil used in Chevy 305's in taxi's (multi-year 10W-40 oil test fleet in suburban Chicago area cabs) went the distance (100K) without destroying the engines.