I just bought a 1981 300SD with 316k miles on a broken Odo. I normally use a Synthetic, which one do you recommend? I am using shell Rotella normal dino oil 15-40 in it currently for it's first oil change with me, however I want to change to a Synthetic. Which one? I looked up on the VW TDI forum web site and found that they recommend the following:
"Oils which are suitable for the full recommended oil change interval in all climates include, but aren't limited to:
Mobil Delvac 1, 5w40 (full synthetic, a reformulated version of Mobil 1 which is intended for diesel engines)
Chevron Delo 400, 5w40 (full synthetic version)
Shell Rotella T (full synthetic version, not to be confused with Rotella SB synthetic blend or regular Rotella T non-synthetic)
Amsoil Series 3000, 5w30 (full synthetic, CH-4 rated)
Amsoil High Performance, 10w40 (full synthetic, CH-4 rated)
Amsoil semi-synthetic 15w40 (CH-4 rated and high quality, but almost as expensive as the full synthetic, and higher viscosity at low temperatures)
Redline, synthetic version (make sure you get the type meant for diesel engines, with the CG-4 or CH-4 rating)
a. There are intermediate classes of oils in between full synthetic oils and conventional oils. These include synthetic blends, and so-called "Group III" hydroisomerized oils, and are also available in viscosity ranges suitable for all climates. They include:
Shell Rotella SB (synthetic blend)
Petro-Canada Duron, various viscosity's (Group III, various grades available, ensure CG-4 or CH-4 rating on the bottle)
Castrol Syntec 5w30, 5w40 (Group III - note that this oil is frequently recommended by VW dealers but is NOT rated CG-4 or CH-4, and isn't a full synthetic - which calls into question what the dealer is telling people ... this forum is generally of the opinion that Castrol Syntec is not the best choice for this engine)
In warm weather, a good-quality non-synthetic oil meant for diesel engines with CG-4 or CH-4 ratings may be used. They're not suitable in cold weather due to reduced cold-pumping properties, and it's prudent to shorten the oil change interval because non-synthetic oils may not resist breakdown at high temperatures as well as the synthetic oils (remember that turbocharger). These oils are much easier to find. These include:
Mobil Delvac 1300, 15w40
Shell Rotella T, 15w40
Chevron Delo 400, 15w40
Beware of other brands that claim to be diesel-rated or turbo-rated, but are actually just plain cheap. Use the good stuff. If you doubt this, ask transport truck drivers that own their rigs what they use. Chances are it will be Delvac or Rotella.
In cold weather, if CG-4 or CH-4 rated synthetic oil cannot be found, regular Mobil 1 rated CF in viscosity grades 0w30, 5w30, or 10w30 may be used, but with a shortened oil change interval because this oil doesn't have as much capability to handle soot".
I also need advice on using Willie Nelson's Bio Diesel B20 in my 300SD. Any thoughts. It is available here in San Diego! YA!

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smartpoageSD
1981 300SD with 316k, Shell Rotella Motor Oil, soon to switch to Synthetic, Michellins and running Willie Nelson's Biodiesel B20
1987 Mazda pickup 111k on Mobil1
1999 Toyota Sienna 96k on Mobil1