Rotella T6 -> 5w40 vs 15w40?

[Yata-Garasu_imp]

If I lived and rode in Texas during the warm seasons, I would consider 15W40 and experience and understand its performance on the bike. 5W40 is useful during winter and summer riding in southern Ontario.

Air cooled V-twin riders often use 15W40 even in the northern regions of North America.

Many Moto Guzzi riders use 10W60, as per the manufacturer's recommendation.

I use 15w40 in my two Honda VT750s, the Rotella T4 dino flavor. It's the perfect oil for those bikes, but those are liquid cooled V twins.

In my experience, 15w40 was not a good match for the air cooled CB1100, even for Texas summers

Lots of extra valve ticking coming from the top of the engine, all last summer.

I went with the T6 15w40 in the CB1100 because I thought the synthetic version might be more forgiving during the cooler winter riding months and in fact it was fine, comparable to the Honda GN4 10w40 that I used the year before.

The valve noise faded somewhat once the T6 had some miles on it, but it was never as quiet as it is now with the 10w30.

I should probably start a separate thread about my experience with T5 10w30 in my CB1100. It's not MA2 rated, but so far it's doing a great job. Better, in fact, than the two other MA2 spec'd oils that were in it before, including a Honda branded oil.

There's too much fear and insecurity about MA certification. It's early days yet, but I'm willing to bet that the T5 is going to be an excellent oil for the CB1100.

I fact, I did bet... That's why I decided to fill my CB1100 with T5 despite the lack of MA letters on the bottle.

I would venture that the 5w40 is probably a serviceable oil for the CB1100 as well, but it might shear quicker than other oils with fewer Viscosity Index Modifiers.

The main thing I'm trying to say here is that, despite the hot Texas summers, the 15w40 wasnt a good fit for my CB1100.

I hope this info is helpful for someone considering Rotella for their CB1100.