I've been wanting to do some updated researching of engine oils for use in the DMC. Lots of info & mis-info/wives tales & the like on the internet. It makes it hard to be confident of anything. Bottom line, I've been using Mobil 1 15W50 with great results but I'm thinking of trying Shell Rotella T 15W40 or Chevron Delo 15W40 (both are rated for diesel use & are heavy duty oils). Since I took the time to research the information, I thought it would be good to share it here for others to benefit from a single source of info.
Basics: the DMC manual calls for 10W-30, 10W-40, 15W-40, 20W-40, for my weather conditions (southern PA) & 20W50 for weather over 64F. Of those, I understand the 10Ws are not recommended because they are a bit light at startup. I tried 10W30 Mobil 1 one season & the engine was noisier until it warmed up.
DMCH recommends Castrol GTX (conventional) 20W-50. I believe Dave Swingle at DMC Midwest likes Mobil 1 15W-50 (full synthetic) which is what I have pretty much always used since I got mine in 2008. My engine has been spotless when I've been inside it, so I know it keeps things clean.
The big argument is that we have a flat-tappet design for our valve lifters & it's metal on metal wear. Many think that we need ZDDP (Google it) levels of 1000ppm or higher. These 3 links provide decent detail in a brief read.
- http://jalopnik.com/pat-goss-debunks...oil-1443647531 (watch the video)
- https://www.bobistheoilguy.com/forum...&Number=111622
- http://www.opelclub.com/ZDDP2.pdf
Then there are these 2 posts of overlapping data of a guy doing independent testing showing the actual zinc & phosphorous levels as well as a wear pressure rating. Of the oils discussed, they rank in this order from highest wear pressure protection to lowest. All are good, but you can see the differences. I pulled out the commonly available oils from the list that are also in the DMC owners manual (excluding the 10W oils). Notice that the 4 conventional oil have better wear pressure than the synthetic Mobil 1. DMCH's recommendation appears to have the best pressure wear rating & the 3 popular diesel oils are very similar. I find it surprising that the Mobil 1 full synthetic is the lowest of the group, but I still consider it a great choice.
- 20W50 Castrol GTX conventional, API SN = 96,514 psi
- 15W40 CHEVRON DELO 400LE, conventional, “Load Carrying Capacity/Film Strength” = 73,520 psi
- 15W40 MOBIL DELVAC 1300 SUPER conventional, API CJ-4, CI-4 Plus, CI-4, CH-4/SM, SL = 73,300 psi
- 15W40 SHELL ROTELLA T conventional, API CJ-4, CI-4 Plus, CH-4, CF-4,CF/SM = 72,022 psi
- 15W50 Mobil 1, API SN = 70,235 psi
- http://www.chevelles.com/forums/18-e...-thoughts.html
- http://www.sccoa.com/forums/showthre...**Good-read*** (Same list as above, but filtered to only list oils with ZDDP levels of 1100 or higher)
Here is some more if you want to dig deeper at some of the better information I found when searching.