KennedyDiesel
Veteran Member
A long time ago GM used to warn specifically AGAINST the use of wide viscosity range oils in diesel engines.
Something about viscosity range extender "residue" accumulating under bottom rings and leading to ring failure - as I said, long time ago so I'm not remembering the details at all clearly.
It might be worth a search though.
This was back in the primarily petroleum days where they were trying to swing 10w40 etc. Synthetics can handle this swing without the issues that used to be.
What will the heavier grade do in the Summer to give you peace of mind?![]()
It was explained to me that a compression ignited engine (diesel) would be best served by a 40w oil to help in cushioning the shock loads of combustion. Also heat is often much higher in a diesel engine oil.
I thought you needed a CJ-4 oil? Amsoil ACD is CI-4+ and could be considered a thinner version of AME 15W-40. I don't know why they are trying to talk you out of running the oil you want to run. Amsoils new CJ-4 oils are quality products and I would use the 5W-40 in an instant if I needed a CJ-4 oil. I run ACD in a mix of cars and equipment, from generators and mowers to my daily driver. All gassers by the way. I have AME 15W-40 in my Kioti and would not have it any other way. The Kioti only spec's CC or CD oil so CI-4+ oil is a no brainer. I started the tractor this morning with no effort at all even though it was 29F. Not nearly as cold as you will see but for us thats pretty cold. If I do decide to use a 30wt it will be ACD, buy why when AME is working so well.
What does the owners manual call for? I may have missed that, but I know you wanted a CJ-4 oil so I was wondering if that was the spec in the owners.
One thing to note about Amsoil is they do NOT test for certification to the various API ratings. They will use terms like: "Recommended for API CJ-4" but do not wear the seal of approval. They make a fine oil and this does not make them a bad company, but it is a bit shady.
I run Mobil Delvac 1 5w40 synthetic aka: Mobil Turbo Diesel Truck. I use this in my Dmax turbo diesel trucks as well as my turbo diesel 3720 Deere. Second choice would be Delvac 1300 15w40 which is what I use for break in etc.
I also use Delvac 1 in:
Deere 455 garden tractor
Polaris Ranger 700XP
Honda Rincon
Honda EU6500is generator
Honda EU2000i generator (from day one)
Ryobi 4 stroke string trimmer
None of these call for a 5w40, but the oil far exceeds the requirements and has served me well.
I have run the Amsoil 5w30 synthetic in my truck under heavy use and the analysis was NOT good.