Like most riders on oil questions, I have my opinion but my opinion is based upon 50 years of riding and also reading several technical 'white papers' about synthetic oils. Up until trading in several bikes, I owned road 5 motorcycles (1999 Valk Interstate, 02 VTX1800C, 05 Rocket 3, 09 V-Max1700 and 09 CVO FatBob 110. I also owned 3 other bikes that my significant other used, 07 Honda 750C2, 10 Honda Phantom 750 & 2010 Sportster XL1200L.) We traded in 5 of these bikes and got 2 new ones (2014 Valk1800, 2014 Shadow 750C2) so we are down to 5 bikes which makes it easier to maintain since we have both retired.
I have used AmsOil in all of my bikes for many years, 10-40 in watercooled ones and 20-50 in the Harleys. We also use the AmsOil Severe Gear 70-90 & 70-140 in all of the drive shaft bikes. We ride all year around here in north AL. Riding in temps from 100 down to 20 degrees so our bikes get plenty of workouts. When I sold the 99 Valk, 02 VTX and 05 Rocket 3 they had 108K, 72K and 82K miles of them respectively. Never had any engine problems at all and they still ran great, great compression and never had any clutch problems.
I used AmsOil 10-40 in the new Valk1800 & will put Severe Gear 70-80 in the shaft drive at about 4k miles. The new Valk's engine was quieter and seemed smoother after my oil change but the major change was how much smoother gear shifting was after changing out oil. My take on oil is that 'any good synthetic' will far surpass any of the Dino-oils and will significantly help your engines ability to maintain its compression and longevity. I simply use AmsOil because it is easy to get and after reading the whitepaper comparisons on synthetics, I felt it was slightly superior to the other brands out there. That being said, Mobil, Castrol and all the other synthetics will all do the job much better than any of the Dino-Oils out there. That is all I will say about the topic as everyone has their preferences.
