Diesel verus automotive oil

[gasser]

Here's a real basic question. Do diesel engines operate at a higher temp than gasoline engines? If so, do diesel oils cool engines better than gasoline engine oils? i.e. will diesel oils, like Shell Rotella, cool and lubricate high temp motorcycle engines better than motorcycle oils, even though diesel oils do not have the additives?

[JerryMather]

This has beed discussed already and there are folks around here that only use Rotela in there bikes.

You may be able to find it with your search button.

[rdfrantz]

Diesel engine water and oil temps are very close to that of gasoline engines.

 

Cylinder head temps are only a little higher, a fact managed mostly by their greater mass, but also by exhaust flow, and water and oil volume and flow.

 

Diesel internal cylinder temps are greater than with gasoline engines - so it is here that oils are more greatly stressed than in gasoline engines. Coking is more likely, and the oils will tend to accumulate soot. Both are handled by superior oil filtration systems. The temperature effect is handled by large volumes of superior oil physics/chemistry that retains greater molecular chain integrity. Properties of synthetic oils aid greatly here.

 

The proper term for oils that provide these services is Commercial Grade, not "Diesel", and in fact I don't know of any Diesel Oils at all. These oils receive ratings of C1 to C4 and beyond. The largest value of the oil being graded is its longevity, its ability to provide service in high stress environments - as within a diesel engine - for extended periods.

 

This service life becomes possible with the addition of mineral packages to a superior grade of oil. Contrary to the comment, "diesel oils do not have the additives:, C4 Shell Rotela T Synthetic, as do virtually all C4 oils, has an extensive additive package, and in grater quantity, than "automotive" or non-commercial grade oils. And, that package exceeds the needs of "the average" desires of all the motorcycle manufacturers.

 

Heat transfer, absorbsion, of oils is more related to the oils viscosity, lighter oils doing perhaps no more than 10% better, though perhaps Mitch can pin this down more closely (It's a factor so small to me that I have ceased to care enough to remain mindful of the details). "Diesel Oil" is not physically different from any vehicle engine oil - their chemistry is petroleum-related. Virtually all synthetic oils begin life as petroleum oil - which is then modified, syntesized, into molecular arrangement that resists deterioration under temperture/pressure. The "gunk" its made of, and thus its other physical properties, like heat absorbtion, is the same. It is not "something else"; It is Engine Oil.

 

I am unaware of any engine failure attributed to lubricant failure being reported about our bikes.

 

The summary conclusion of The Oil Threads is that any "top line 'automotvive' oil" will work just fine in any motorcycle so long as it and its filter are frequently changed. Six thousand mile change intervals are wholly prudent where the oil is not also used to lubricate the transmission/gear box (which tends to "chop up" oil molecules). The other two stressors I find are excessive heat, which degrades lubricity greatly, and contaminants.

 

I changed my RT oil at 3000 mile intervals because analysis showed two things. First, there was a high level of silicates which came from "sand" bypassing the air filter. Second, viscosity index rose because my RT was subject to 300F+ temps in stop and go traffic. Sysntetic oil did not make sense in that scenario because contamination required the frequent change. Absent that (less desert living and riding), analyzed syntetics showed good heat tolerance across 6000 and even 9000 mile change intervals (Rotela T C4).

 

I use Rotela T Synthetic in all my motorcycles because I have tested that it meets the needs those bikes manifest. For me "The Topper" is it's 5W cold starting protection since my bikes are frequently started in 5F to 20F temps. Startup is the time the greatest amount of engine wear accrues, so...

 

 

Best wishes with your own choices.