Regarding the mention of Rotella oil.....I have heard great things about it. I understand it's a Shell Oil product. But when I look for it, I only find 15/50 Synthetic Rotella with a note on the bottle "for Diesel engines". Is that okay and just saying it's ALSO good for diesels or is that just for diesel use
I'm in AZ, where it has been known to drop below 80F in the winter once in a while. But I wouldn't even consider using anything thinner than a 15w50 or 20w50 in a motorcycle, especially an air cooled single or single crankpin v-twin. These engines put a heavy load on the con rod and crank bearings, and you need an oil with all the load bearing ability you can get. I have owned singles, parallel twins, v-twins, triples, inline and horizontally opposed fours, and a horizontally opposed six (Goldwing) I've never use anything but 20w50 in any of them, and never had an engine failure. Harley recommends only 20w50 in their engines. I don't see any problem with any type of oil, conventional, semi synthetic, full synthetic, car, or motorcycle specific, as long as that last number is a 50. I'm using a very expensive full synthetic motorcycle specific oil in the RE, but I intend to follow the oil change intervals in the manual. I have a couple of other bikes I use cheap conventional 20w50 oil in, but change it every 1000 miles. 10w40 or 15w40 might work ok in a four or six cylinder engine, they do not have anywhere near the stress on the bearings as a single, especially a long stroke single like the RE.
I have read that before, and other similar information in trade magazines. I grew up with the old way, and will stick with it. Notice RE recommends 15w50 oil, Harley-Davidson recommends 20w50 oil. They do not recommend 0w10. My Vulcan 750, which is liquid cooled, says 10w40 right on the oil filler cap, but the manual also recommends up to 20w50 (which is what I use) for higher ambient temperatures. And as far a liquid cooled engines, ambient temperature is still very important when choosing an oil. A liquid cooled engine does NOT run at a constant temperature regardless of ambient temperature. Every liquid cooled bike I've ever had always ran much hotter in the summer than in the winter. In the winter, my VN750 runs in the low to normal range on the gauge, in the summer it runs way over toward the hot side. A "liquid cooled" engine is still air cooled, it just has an extra step. Most liquid cooling systems on bikes are marginal, especially in a place like Phoenix, AZ. The numbers DO matter. A 20w50 oil is measurably thicker than a 10w40 oil at any given temperature. I use straight 60w oil in my drag race car. The engine was built for that oil, with the proper bearing clearances. In an engine, heavier oil does have more fluid friction, but it is a worthwhile trade off, because it protects your bearings. This thing about wear at start up is largely a myth under most circumstances. If you ride the bike often, all the internal parts of the engine stay coated with oil, and the thicker then oil, the longer they will stay coated. Thick oil sticks to metal, while thin oil will run off faster. I have taken apart engines that sat for over a year, and found everything was still coated in oil. Thicker oil also provides better ring seal. In an older engine that is burning oil, switching to a thicker oil will lower oil consumption, and also provide more cushion for worn bearing clearances, making the engine last longer.As for diesel oil, you can use it in any engine. It used to be much better than regular oil, because it had a much higher content of zinc and phosphorus, which are good for engines. This was also the case with motorcycle specific oil. But more recently, and again because of the EPA, these beneficial elements are being removed from all oils.
Shell Rotella 15W40 is JASO MA rated and safe for wet clutches. I have used it for years in my Yamaha XS650. I have not used it in my Bullet but I believe it would be just fine if I did.
Also remember that a failed Catalytic converter is not covered under the emission warranty if you do not follow the specs. It probably the most expensive single part on the bike.
I don't believe EPA oil and a too lean A/F mixture are good for my engine.
I just heard on the news today, of another government agency scandal. Seems the EPA has also become a "rogue agency".
You can blame the farm lobby for ethanol....