Hey there, All - I hope this finds you well and healthy and for the most part, sane (normal disclaimers apply here).

I have an '81 300TD-T with about 215 *very* well-maintained & documented miles on the clock. It has always had it's typical and expected territory-marking oil drips from various points under the engine and transmission. Nothing excessive or worrisome. This car lived its entire life in the SF Bay Area of California, and a charmed life indeed. In December 2020, my family decided that CA was trying just a bit too hard to kill us all, what with the fires, smoke, cost of living, crime, cost of doing business blah blah blah, and moved 'back to bedrock'; Asheville, NC to be precise.

The car was shipped out here, sat for about a month and it was cold cold cold. After my first distance drive (Asheville to Atlanta, about 2hrs 45min on the highway), I parked the car in my business partner's driveway for the afternoon while we had a "high level corporate meeting" on his back deck, sharing Panamanian Geisha coffee and vintage cuban cigars. About four hours later, I went out to the car and noticed a sizeable puddle of engine oil under the car, which was nose-down by maybe 2 degrees. It all seemed to be coming from under the bell-housing area, but you know how these things are; it's hard to tell sometimes. The puddle (keeping in mind how far diesel engine oil spreads when it hits the pavement) was about 6" in diameter. I rolled the car down to a level spot in the driveway and checked the oil. It was down exactly 1qt, and I checked it and topped it off before embarking on the 150mi trip.

I brought the car to a specialist in Atlanta, and they pressure-washed and put it up on the rack and determined that yes, this was in fact mostly coming from the rear crankshaft seal. Knowing full well what this means, I topped it up and drove it home. It was down a full quart upon the end of those same 150 or so miles.

Since January, I have been monitoring. Some days, after driving around town or highway, it leaves nothing more than it ever did - a few random drips from here and there. Other days, it leaves slightly more behind (but never what it dropped that first day). I have since determined it is dripping from just to the right of the bell housing (as you face forward).

Using 100mi increments as a basis for analysis, I have found that:

100 miles of around-town driving = less than a 1/4qt of engine oil loss.
100 miles of mixed driving (town and short highway) = 1/2qt of engine oil loss.
100 miles of highway-only = 3/4qt+ of engine oil loss. More if it's hilly miles.

To me, this seems like not so much a rear crankshaft seal problem (which is seeping, I grant), but a problem with pressurized oil, and, based on the precise location of dripping, it's under the turbo area. There is engine oil on the bottom surfaces aft of the engine, and there is also oil spattered lightly on the tailgate, which could be coming from the exhaust, too, after highway driving.

What's confusing me is the variability of engine oil dripping on the driveway. I'm inclined to think that this is a compound issue of leak and added consumption. It all started once the car experienced its first actual winter and deep cold temps. Car now lives in the garage with a radiant-heated floor, but those first few months after moving, it had to be outside.

Any of you resident experts have any food for thought? What I don't want to do is assume it's the crankshaft seal exclusively, because the engine otherwise runs amazingly well and efficiently. A turbocharger rebuild wouldn't be an unwise choice regardless of oil problems, and even if an engine rebuild is deemed necessary to get to that crankshaft seal, the turbo would be rebuilt anyway.

Thanks, and be well!

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Filmmaker, Dad, Citizen of the World in Asheville, NC
=== current vintage stable ===
'73 VW Thing, '09 BMW 328i Convertible, '07 Honda Ridgeline, '94 Chevy Step Van