Oil viscosity - more difference than I would have thought

[theholycow]

If manufacturers were specifying insufficient oil, wouldn't engines commonly be failing prematurely from lack of lubrication?

[bowtieguy]

not likely, especially soon or immediate evidence of such. i wonder how much engine life is SHORTENED by using 20 weight in warm climates, excessive idling, daily a/c usage etc?

shortened or premature is relative to be sure. 100k? 200k? 300k? what is fully mature?

[bowtieguy]

here's an interesting read...http://www.calsci.com/motorcycleinfo/Oils1.html

Jay may find it helpful as it deals mainly w/ motorcycle lube. anyway this guy claims 0w20 in a heavy duty app(like hard driven motorcycles) is a no-no. he also dismisses the study(you know how i feel about them and their often slanted approach ) of cab engines run on conventional oil.

do we all drive hard enough to warrant extra protection? likely not most, but hey, it's cheap insurance.

[imzjustplayin]

Originally Posted by bowtieguy

here's an interesting read...http://www.calsci.com/motorcycleinfo/Oils1.html

Jay may find it helpful as it deals mainly w/ motorcycle lube. anyway this guy claims 0w20 in a heavy duty app(like hard driven motorcycles) is a no-no. he also dismisses the study(you know how i feel about them and their often slanted approach ) of cab engines run on conventional oil.

do we all drive hard enough to warrant extra protection? likely not most, but hey, it's cheap insurance.

I wouldn't call it insurance if you're using a heavier weight oil than specified since that could easily void the warranty if they ever figured it out. If you're driving your vehicle "hard" to begin with, then this is totally irrelevant since you should not only be changing your oil more frequently but also should expect to rebuild the engine much sooner.

[bowtieguy]

um, perhaps you've heard of warmer climates and high humidity. we've have had near 100*F temps all summer in florida. overheating can happen to anyone, anytime. i WANT that insurance. besides the moot point of $$$ and time savings, as well as conservation has been exhausted.

here's a perhaps slanted source who recommends avoiding 0 and 5w20 oils even tho they sell it!...http://www.smartsynthetics.com/articles/5w20oil.htm and warranty loss? HOG WASH!

[i-DSi]

Originally Posted by bowtieguy

... anyway this guy claims 0w20 in a heavy duty app(like hard driven motorcycles) is a no-no.

'This guy' is not alone. Also Honda recommands only one viscosity for my 600cc 16v motorcycle: 10W30.
Following his thoughts:
BHP of my MC and car are the same (approximately 80 BHP), but the engine size of more car is more than double of my mc, so my mc is 'heavy duty' and my car is not. So 0W20 is fine for my car.

[GasSavers_BEEF]

but horsepower can vary greatly from engine to engine due to a lot of factors, a big one being RPMs.

your car probably redlines around 6-7k where as your motorcycle probably goes well over 10k.

a better determining factor would be torque ratings.

I'm not trying to discredit what you say as it may be true but motorcycles in general run really high revs giving them the HP that they have and the flip side being that they have very little torque (relatively speaking)

[bobc455]

Interesting discussion, guys.

As far as I can tell, oil is meant to take up the downward pressure of the piston (across the surface area of the bearing) in order to prevent the bearing race from contacting the crankshaft. Therefore there are several variables that would come into play:
- Diameter & width of the bearing (i.e. the smaller the bearing surface, the higher viscosity oil would be needed)
- Downward force on the connecting rod (i.e. if I were to add a supercharger to a given engine, it might be prudent to use a thicker oil due to the increased combustion pressure - similar for high RPMs) (obviously driving style can affect this too, as can advanced ignition timing)
- Oil pumping characteristics of the engine - higher volume / higher pressure oil pump could utilize a thinner oil
- Bearing clearances

But at the end of the day, a 1 MPG difference for a single movement in oil viscosity is still very surprising to me.

-BC

[theholycow]

When you think about it that way, I wonder if the change in fuel economy indicates that the old oil was not doing its job at all and the metal was riding directly on metal instead of having a film of oil sandwiched between to reduce the friction.

[i-DSi]

Originally Posted by BEEF

but horsepower can vary greatly from engine to engine due to a lot of factors, a big one being RPMs.

your car probably redlines around 6-7k where as your motorcycle probably goes well over 10k.

a better determining factor would be torque ratings.

I'm not trying to discredit what you say as it may be true but motorcycles in general run really high revs giving them the HP that they have and the flip side being that they have very little torque (relatively speaking)

Hi Beef, motorcycles have an ubelievably high torque (relatively speaking).
In my case: Honda motorcycle 600cc 59 Nm, my Honda car 1339cc: 88 Nm.
Meanwhile I read the oil info on Bowies link. The main reason why 0W20 is a no go in motorcycles is because of the friction reducers used in it (bad for the wet clutch).