We were
very reluctant to post this, knowing how oil threads usually devolve into... whatever it is they devolve into.
Y'all know what we mean.
This is simply meant to be a PSA for those of us who use diesel oil in bikes because of their purported JASO MA rating. We'd feel like we were doing a disservice to the KZR community if we didn't share.
We were made aware of a
possibly developing issue with wet clutches when using
the most recent formulations of diesel oil that had performed well with wet clutches in earlier formula iterations. This had slipped under our radar until a Rider on another forum linked to it on the st-owners.com forum.
Many ST1100 / ST1300 Riders cover serious miles every year, akin to Gold Wing Riders. It's not unusual to see ST1300's with over 100K miles on them. Oil threads are an ongoing 'thing' at the st-owners forum.
We, personally, have not had any problems using Rotella 15w-40 dino oil in our ST1300A, or one of our '74 Z1's. But, we bought the 15w-40 gallons we have on the shelf a few years ago on Black Friday sales, and the formulas & API ratings have changed since then. We only used the full synthetic 5w-40 once in our ST1300A, because slmjim didn't like the way the clutch & tranny felt.
The short version:
Motor oil producers modify formulas routinely to account for changes in motor design & materials and, changes in emissions laws. There's chatter that some recent formulations of Shell Rotella 5w-40 full synthetic in particular may be causing wet clutches to fail in ST1300's. The linked threads are the sum total of what we've read so far. Conflicting info, some facts, & many opinions to wade through. Draw your own conclusions:
www.st-owners.com/forums/threads/new-tre...-diesel-oils.184954/
www.st-owners.com/forums/threads/shell-t...e-rotella-t6.184924/
www.st-owners.com/forums/threads/rotella-t6.183960/
We've not researched beyond what is contained in the linked threads above 'cause we value our time & sanity. We'll just offer our opinions:
Oil is literally the lifeblood of an ICE. Once our stock of old-formula dino15w-40 Rotella diesel oil is used, we'll bite the bullet & only use motorcycle-specific dino (in Z1's) and full syn (in our CB750 Nighthawks & ST1300A) oils that have the JASO MA symbol & JASO certificate number on the label.
Good Ridin'
slmjim & Z1BEBE