In my 80 240D and will be running same in 83 300D. I added a coolant heat exchanger (made it myself) and a homemade 12v fuel heater with a switch in the cabin. Can runs flawlessly and started this morning at 40degrees with no problems. Will be in 20s tomorrow but I'm not worried. Using virgin oil like that is alot easier and more predictable than waste oil. You should be fine with as much of it as you can afford. Of course, there are no guarantees...

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Rich Mason
Chapel Hill, NC
1990 300D 285k miles
1993 VW Cabriolet converted to 1.6 TD
1985 VW Westfalia 1.6 TD