Synthetic oil - Diesel or Gas rated ?

[mike90045]

So, is there anything in gas engine Synthetic oil, that, with reduced hours, would damage components of a diesel engine?  NAPA parts often has their house brand synthetic on sale for plain oil prices.  I got a case for the high wheel trimmer and chipper and am thinking of using in the diesels.  I suspect the diesel oil has more detergent in it to deal with carbon better.  But by keeping change intervals short, any other problems ?

[38ac]

Glort pretty well summed my feelings on the matter
 Any oil you can get now is better than what was available when the engine was designed
 Any clean oil is better than any contaminated oil
 Way too much well meaning attempted rocket science is written on the subject

[32 coupe]

It has always made me laugh when guys get on here and rave on about
what oil should they use in their Lister/Listeroid.

I believe ANY oil today would be better than the "lard" that was available 50 or 100
years ago.

Just my thoughts.

Gary

[dieselgman]

There is one significant departure from the "any clean oil" mantra... it involves the initial break-in period for a new engine where you need the rings and bores to wear and adjust. A non-detergent grade is normally required or recommended for this purpose.

All other times, I agree that any modern diesel-rated oil will do an excellent job of keeping your machine properly lubricated. Keeping it clean (frequent changes and/or filtration) becomes the primary service objective.

dieselgman

[mike90045]

I'm not talking of lubricity qualities, but of some additives that erode metals, like something in 90W differential oil, damages engines (or is it the other way around?)

[dieselgman]

Reminds me of the guy recommending the very heavy EP gear lubes for his CS Listeroids. I guess that 140 wt. would tend to close up some of the gaps and loose clearances...  

I have heard and read various comments - especially about compatibility of additives, and have experienced severe oil gelling in some of our air-cooled NG Listers. Polymerized oil is an absolute nightmare to get back out of a pressure-fed oil system.

Combustion of diesel fuel produces differing compounds (as far as the lubricating oil is concerned), from gasoline combustion.

In a nutshell (and severely abbreviated): Not "rocket science" except perhaps for the testing and design phases of product development.

Besides lubricity and viscosity characteristics, the additive package is the next important factor in determining the performance level and design of a modern lubricating oil.

Corrosion prevention is one of the major factors in particular that a diesel engine oil is designed to deal with (besides wear and deposit control) ... The idea that an off-spec oil will directly "cause" corrosion is a fallacy, however, in a diesel engine with substantial Sulphur compounds entering the lube oil and becoming acidic - bearings will erode as a result. The modern API CD rated oils are buffered to reduce or prevent this from happening. API SG or gasoline engine rated oils may not have this same performance characteristic. The net result can be bearing corrosion from acidic oil if using lesser grade oil without the correct additives.

Use a diesel rated oil API CD, CE, CF and so on in your Lister slow-speed. Change it frequently even if the engine is not run a lot of hours.
Each engine manufacturer has come up with their own set of recommendations based on a long list of oil system performance data that is very well documented and explained. See "Engine Manufacturer's Association" publication EMA Lubricating Oils Data Book.

dieselgman

[oldgoat]

You may have been thinking of E.P. gear oils which contain sulphur and  phosphorus compounds to deal with the sliding friction in gear trains. They are corrosive to the bras and copper alloys used in gearbox bearings and synchro cones.

[buickanddeere]

Until WWII with high power density aircraft engines sometimes operating without oil pressure during dives etc. There no particular "motor oil". .Gear line oil was thick oil from the distillation tower with a pinch of powdered sulphur added by the driver or mechanic  in heavily loaded , high shear applications.  .in fact GL-1 gear oil hasn't really changed since WWI. the Motor oil was mostly untreated mineral oil straight from the distillation tower well into the 1950's. The first gas turbine engines also forced development of lube oil.