AtomicNumber53
Thread starter
Originally Posted by JAG
Because of the large concentration of viscosity index improvers in 0W-50 oils, I would not use them in a motorcycle calling for a particular xW-50 viscosity grade. I wouldn't use 5W-50 either.
OK... What about a bike calling for a particular xW-40 viscosity grade? Wouldn't a 5W-50 be an option here?
And because of the VIIs breaking down, wouldn't a 0w-60 or 5w-60 oil be an option.... If such an oil existed?!? (You know it's coming!)
Originally Posted by JAG
HTHS viscosity is much more important than kinematic viscosity at 100 C because..... In used oils, the percent decrease in HTHS viscosity has been found to be around 1/2 of the percent drop in kinematic viscosity at 100 C. In a motorcycle, the kinematic viscosity at 100 C of a 0W-50 may be expected to drop from 17 to 13 cSt (or even lower) which is around 25% drop, so HTHS should drop by around 12.5%.
I saw a chart comparing oils, and the Amsoil MCF 10w-40 was shear proof! After 90 cycles, there was no shearing on this oil. This is the only xW-40 grade oil I would really want to consider on a bike calling for such a viscosity. Otherwise, it makes more sense to just give a little thicker oil that we know will shear down to a 40 weight at operating temps.
The only problem is that there are UOAs of this Amsoil MCF 10w-40 that are definitely breaking down to a 30 weight, even tho it's "shear proof" in that chart. So if that's the case, it seems like a 5w-50 with HTHS of 4.7 (higher rated than the shear stable Amsoil MCF w/ 4.5 rating!) could be a very good choice for a synthetic that offers better protection throughout the temp range for many more miles. Guess there's only one way to know for sure, though -- UOAs?
Because of the large concentration of viscosity index improvers in 0W-50 oils, I would not use them in a motorcycle calling for a particular xW-50 viscosity grade. I wouldn't use 5W-50 either.
OK... What about a bike calling for a particular xW-40 viscosity grade? Wouldn't a 5W-50 be an option here?
And because of the VIIs breaking down, wouldn't a 0w-60 or 5w-60 oil be an option.... If such an oil existed?!? (You know it's coming!)
Originally Posted by JAG
HTHS viscosity is much more important than kinematic viscosity at 100 C because..... In used oils, the percent decrease in HTHS viscosity has been found to be around 1/2 of the percent drop in kinematic viscosity at 100 C. In a motorcycle, the kinematic viscosity at 100 C of a 0W-50 may be expected to drop from 17 to 13 cSt (or even lower) which is around 25% drop, so HTHS should drop by around 12.5%.
I saw a chart comparing oils, and the Amsoil MCF 10w-40 was shear proof! After 90 cycles, there was no shearing on this oil. This is the only xW-40 grade oil I would really want to consider on a bike calling for such a viscosity. Otherwise, it makes more sense to just give a little thicker oil that we know will shear down to a 40 weight at operating temps.
The only problem is that there are UOAs of this Amsoil MCF 10w-40 that are definitely breaking down to a 30 weight, even tho it's "shear proof" in that chart. So if that's the case, it seems like a 5w-50 with HTHS of 4.7 (higher rated than the shear stable Amsoil MCF w/ 4.5 rating!) could be a very good choice for a synthetic that offers better protection throughout the temp range for many more miles. Guess there's only one way to know for sure, though -- UOAs?