Originally Posted by dx92beater
Supposed to be getting this car from a co-worker soon. Has 180k miles. I know jack about diesels but the price is right.
What are some good oil choices?
As has already been discussed, most every 5w40 oil will work okay for a 10k-mile oil change interval. All 5w40's are synthetic. Some are better than others, but not enough difference to matter over the next 200k-300k miles or so. Those ALH engines are bullet-proof. I've always used M1 Turbo Diesel Truck or Mobil Delvac 1, but the Shell Rotella guys seem to have had good results too. Others use Schaeffers or Amsoil, but all 5w40s are appropriate.
You mentioned that it has a 4-speed automatic transmission, which is likely to become a problem if it is not already. There's a cottage industry of TDI mechs swapping the automatic for the 5-speed manual. It's likely to cost about $2000, so the question is whether the rest of the car is worth it. If it's rust-free or nearly so, then I suggest you plan on doing the swap and then keeping that TDI forever. TDIs with the automatic are worth about $500-1000, with the 5-speed MT between $2000 and $4000.
Remember that the timing belt interval is 100k miles, and if there's any uncertainty about when it was last replaced, or what other parts were replaced besides the TB itself, or whether it was done by a competent person, then schedule the work soon and use a TB kit from a reliable vendor. If a kit is priced $100 less than what others are selling for, then it's not a good kit.