Engine/Transmission (1998.5 - 2002) Another Amsoil question

[Mtngoat]

What are the benefits between these 2 oils and which is best for our Cummins?



SAE 15W-40 Synthetic Heavy Duty Diesel and Marine Motor Oil



Synthetic Blend 15W-40 Diesel Oil



Thanks!!



Robin

 

[RowJ]

Which Amsoil

I recommend the HD 15w-40 (Diesel & Marine).



The Blend is just that. A Blended synthetic - Partial synthetic & partial Mineral oil base (dyno oil); it is apparently geared towards a more economical market.

I believe the Heavy Duty Diesel (15w-40) is the only one rated at CI-4. This is the latest diesel oil API rating which has to do with greater soot control over previous ratings-(CG-4, CF-4, etc). CTD's do not require CI-4, as does Mack and some others, but why not use it if you can get it. Lower soot = cleaner insides on any diesel engine.

Some Amsoil dealers will probably chime in with more specific differences.

 

[RowJ]

Just checked - The blended Synthetic is also rated CI-4.

Problem I have with Blended synthetic oils is you never know what % of the oil is synthetic. There are no govt regs specifying it has to be at least 10% or 20% etc.

According to Amsoils specs - you loose 15 degrees on pour point, from -47 for full synthetic diesel & marine to -32. This has to do with oil thickening up in cold weather. Also loose some on other end-flash point.

Price wise-blended synthetic is 20% less. Personally, I would use the amsoil blended before I would use a national brand synthetic (Mobile I, Castrol, etc. ) due to excellent additive package. But why not spend a few extra pennies to protect a serious investment (our CTD) and go with the best you can get.

Easily justified if you go 10,000 miles between oil & filter changes (7500 for heavy towing). I believe the Amsoil full synthetic will do this easily.

 

[tmarti96]

Amsoil syn oil

I tow RVs for a living and have 20,000 on present oil( Amsoil HD Marine and Diesel 15W40 and it still checks 'good for continued use'. I change full flow filters at 7500 and bypass at 25,000. Truck has 200,000 miles on it and uses about 1 qt every 4,000 miles. I can live with that.