Diesel oil or not.

   / Diesel oil or not. #11  
It was the Rotella T6 5W-40 that I had issues with [now available in 15W-40 (JASO MA/MA2), 5W-40 (JASO MA/MA2) and 0W-40 (not JASO rated!), but in the past, T6 was only available in 5W-40]. I now use T6 15W-40, and my issues disappeared. I agree, the cold viscosity difference seems trivial. I just have to go with what I experienced. It was an issue two years, two oil changes, in a row, until I switched to the 15W-40 viscosity. I love the Rotella T6 oil for my motorcycle. I bought Shell transmission oil for my tractor, based on my past experiences; used Shell Rotella in my tranctor's engine, when I changed that after I bought it, as well. Great products, great prices, IMO.

I know that more modern car engines are very intolerant of oils which are outside of their specified viscosity ranges (voids the warranty), so I suspect diesel engines are likely running with similarly tight tolerances, which won't do well with oils outside of the specified viscosity ranges. Just offering free advice, worth every penny paid for it. LOL! Cheers!
 
   / Diesel oil or not. #12  
I have a Kubota 900 RTV with the diesel engine in it. It's time to change the oil and it calls for 10w-30. I have a bunch of Pennzoil Platinum High Mileage 5w-30 and was wondering if this could be used. It does not say anywhere on the jug about using it in a diesel engine. Would this oil be ok for this application? Thanks. RRM
Diesel engines ignite by "compression". They require the additives in "C" rated oils, not "S" only which is for "spark" ignited systems. Diesels run higher compressions and have higher wear potentials and need the extra additives. Usually C rated oils are also rated for S service but not vise-versa. So when viewing the starburst look for the C rating.
 
   / Diesel oil or not. #13  
The difference between 5W- and 10W- is trivial on a motorcycle. At 70°F and above they are essentially the same.

If you clutch slipped then it had more to do with the specific oil and nothing to do with 5W. Many automotive oils simply slip in the wet plate clutches of motorcycles. The only independent assurance of good clutch performance is to look for JASO MA or MA2 compliance.

In years past Shell Rotella T6 5W-40 has been a very popular motorcycle oil. Clutch works just fine using this oil in my Yamaha FJR, but the transmission doesn't click between gears as nicely as it does with other oils. Automotive Mobil-1 15W-50 also clutches fine but shifts poorly. And some Castrol motorcycle-specific oils similarly. A discontinued Valvoline synthetic motorcycle oil worked best but am now using the WPS store brand "Firepower" 10W-40. Shifts nice, clutch grabs hard. Hate that brand name but it is apparently a good oil.
Mobil 1 markets 0w-XX synthetic oil. What that means is that it stays fluid at any temp down to some level. The XX is for the high temp operation which is important to the engine design which, depending on things like manufacturing tolerances to use the thinner (more efficient) oils, so today you see a lot of XW-20 oils specified in Honda cars for example... I have one. My Silverado is specked for 5W-30...different design tolerances. Mobil 1 0W-20 or 30 is guaranteed to satisfy the requirement for 5w-XX oils.
 
   / Diesel oil or not. #14  
Thinner oils have more to do with fuel economy rating’s here in NA. The same vehicle/engine in Saudi Arabia will most likely have a heavier oil recommendation like 10w40 or 15w40…😉
 
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   / Diesel oil or not. #15  
Thinner oils have more to do with fuel economy rating’s here in NA. The same vehicle/engine in Saudi Arabia will most likely have a heavier rating like 10w40 or 15w40…😉
Numerous sources mention that initial startup, oil starvation is the most destructive time of engine operation. Low W ratings are your friend!

I am a holdover heavy oil preferrer guy. Used to be I ran15W-40 in my 5 liter '88 Ford P/U. If the truck sat for awhile, upon start up, I'd hear lifter clatter for a few seconds, same thing when starting after an oil change.

I switched to 10W-30 and never heard it again.......clatter is wear and tear with hydraulic lifters especially and I kept my oil clean....regularly changed and drove 20 miles one way to work.....so it wasn't all sludged up and I bought it new.
 
   / Diesel oil or not. #16  
Two very important things are critical to diesel engine life. Clean oil. Clean fuel. A third would be the correct oil.
 
   / Diesel oil or not. #17  
Could use it but change at 100 hours instead of 200 because of carbon buildup. Think this is the only difference between gas and diesel engine oil: more/special detergent to keep carbon in solution in diesel oil. Did it once on our 1983 240D Benz.
 
   / Diesel oil or not. #18  
Diesel engines ignite by "compression". They require the additives in "C" rated oils, not "S" only which is for "spark" ignited systems. Diesels run higher compressions and have higher wear potentials and need the extra additives. Usually C rated oils are also rated for S service but not vise-versa. So when viewing the starburst look for the C rating.

The "C" in the API "C" categories is for "commercial," not "compression." The "S" in the API "S" categories is for "service," not "spark." An oil with just an "S" rating will also have the "sunburst" logo containing the words "For Gasoline Engines." Also there are the "fuel economy" API FA-4 diesel engine oils that aren't compatible with the "C" specification oils, and about all needs to be said is to not use them.

The main difference in the "C" and "S" oils is the soot dispersants in oils designed to be used in diesel engines. The emissions systems on new diesels and gasoline engines are also different, and the emissions systems in each can get fouled if the wrong oil is used when the normal small amount of oil is burned through normal operation and the ash ends up going through the emissions system. Most "C" rated oils will also have an "S" rating but there are a lot of "S" rated oils without the "C" rating, as an oil designed to be used in a gasoline engine won't need the dispersants the diesel oil will, and them not being present will have the oil not be able to get a "C" rating. However, a lot of the "C" rated oils that carry an "S" rating as well carry older "S" ratings as some of the components in a typical "C" rated oil are present in quantities that would make an oil fail the newer "S" specifications, so it will instead be rated for an older "S" spec like "SJ" or "SL" instead of a newer one like "SN" or "SP." Zinc concentration in particular is limited in newer "S" specs much more so than in "C" specs.
 
 
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