Oil viscosity options

[Travis Bickle]

Looking in the Haynes manual for my Fazer it says I can use either 10W/30 or 10W/40.

Even worse for my YBR I've got 6 options to choose from (0W/30, 10W/40, 10W/50, 15W/40, 20W/40 or 20W/50)

What are the pros and cons against a lower viscosity vs. a higher one and why would you pick one over the other?

Is it generally accepted that the 10W/30 would give slightly better fuel efficiency and performance whereas the 10W/40 would give slightly better wear protection? Or is that over simplifying it?

Thanks in advance for your input!
____________________
Must Go Faster
1999 Yamaha FZS600 Fazer

[blurredman]

Generally the lower oil viscosity is to maintain oil pressure and viscosity to lower temperatures. Likewise with the the higher ones. You don't want really thin oil in a hot climate, it could be too thin to properly lubricate bearings/cams/lifters/chains/anything -


Too thick an oil in the winter could mean that it doesn't travel to the correct places fast enough to reduce engine-starting and 'warm up' wear.


That said, these days with multigrade oils, it's not so necessary to change your oil to a lower grade for the winter, as it would have been in the past.


10w40 is a good all round, really.


I'm sure i'll be corrected, though.
____________________
CBT: 12/06/10, Theory: 22/09/10, Module 1: 09/11/10, Module 2: 19/01/11
Past: 1991 Honda CG125BR-J, 1992 (1980) Honda XL125S, 1996 Kawasaki GPZ500S.
Current: 1981 Honda CX500B - 91k, 1987 MZ ETZ250 (bored to 295cc) - 38k, 1989 MZ ETZ251 - 49k, 1979 Suzuki TS185ER - 9k, 1973 MZ ES250/2 - 17k.

[Travis Bickle]

I can see how having oil too viscous in cold weather would increase startup wear... but surely by the time and engine is warmed up (to say, what, 90 degrees) surely a 10 or even 20 degree difference in climate isn't going to affect it all that much?

I guess what I'm saying is that in minus 20 conditions your oil is going to be minus 20 at startup.

But it doesn't matter whether it's zero degrees or plus 50, once warmed up your engine/oil temperature is going to be the same regardless???
____________________
Must Go Faster
1999 Yamaha FZS600 Fazer

[blurredman]

Not necessarily.

You can use both 10w40 and 20w50 in our climate.

And yet one is thicker even whilst warm.
____________________
CBT: 12/06/10, Theory: 22/09/10, Module 1: 09/11/10, Module 2: 19/01/11
Past: 1991 Honda CG125BR-J, 1992 (1980) Honda XL125S, 1996 Kawasaki GPZ500S.
Current: 1981 Honda CX500B - 91k, 1987 MZ ETZ250 (bored to 295cc) - 38k, 1989 MZ ETZ251 - 49k, 1979 Suzuki TS185ER - 9k, 1973 MZ ES250/2 - 17k.

[Confusion]

[MCN]

[steve the grease]

It's not like we live in the Arctic circle or Sub Saharan Africa, we don't really have a climate in he UK , just weather.
In manuals there is usually a graph showing temperature and, grades of oil, with lubricants of different grades all overlapping, in the temp range we are likely to get in the UK. As a result , pretty much any of the oils listed for bikes operating anywhere in the world will do for a bike in the UK. 10w-40 does it for me , it's cheap and does all my 4 wheeled vehicles as well as the bikes , so whats not to like .