pleopard
Veteran Member
I realize this has been discussed; however, I'd like to approach it from a slightly different angle. Historically, car and truck diesel engines primarily ran either 15W40 or synthetic 5W40 oil. So, what has changed in modern diesels that now allows the conversion over to strictly 30 weight oils? _Or_, perhaps a better question is, have oils advanced enough that modern 5W30 oils can perform as well or better than 5W40, at least in modern engines? What are the technical reasons for running only 40 weights in the past? I find it much more difficult now to source 505.01 oil that's 5W40. As such, I'm simply running 5W30 (Total Ineo MC3 505.01).
Secondly, is there any hard evidence that a 30 weight oil is not as effective at lubricating a modern diesel engine in a car? If there is any hard evidence, then I find it difficult to believe that VW would allow such oils to carry 505.01 certification. I honestly do have more faith in VW than most people here. The 505.01/507 specs obviously can't be purely for fuel economy and emissions, though I wouldn't be too surprised if they were heavily biased towards fuel economy/emissions. Any technical documents that support using 40 weight oils over 30 weight oils would be appreciated.
Finally, just out of curiousity, are there any 5W40 oils that are 507 approved?
Oils I can probably get are Motul or Fuchs 5W40 with 505.01 certification, but it will be a lot less convenient to get these oils.
Thanks for the thoughts in advance.
Secondly, is there any hard evidence that a 30 weight oil is not as effective at lubricating a modern diesel engine in a car? If there is any hard evidence, then I find it difficult to believe that VW would allow such oils to carry 505.01 certification. I honestly do have more faith in VW than most people here. The 505.01/507 specs obviously can't be purely for fuel economy and emissions, though I wouldn't be too surprised if they were heavily biased towards fuel economy/emissions. Any technical documents that support using 40 weight oils over 30 weight oils would be appreciated.
Finally, just out of curiousity, are there any 5W40 oils that are 507 approved?
Oils I can probably get are Motul or Fuchs 5W40 with 505.01 certification, but it will be a lot less convenient to get these oils.
Thanks for the thoughts in advance.