Motorcycle oil question

[BusyLittleShop]

Originally Posted by ZeeOSix
Blackstone doesn't really know much about tribology.


Mercy Zee... to be fair did you ask them if they know about tribology???


Originally Posted by ZeeOSix
What's their definition of "significant differences".




I gather their testing data shows no evidence of any significant mileage difference between the viscosity grades...

 

[Bonz]

Mileage difference in terms of wear and tear or mileage difference in terms of MPG?

I've read that the super thin oils 0w-20, 5w20, don't promote longevity when you're talking 150,000, 200,000 or more.

This seems to have good backing in terms of the explanation.


"Viscosity and Wear
Thinner oils have less drag, and therefore less friction and wear. Right? Perhaps in the test engine or engines that experience normal operation. But somewhat thicker oils may offer more protection for more severe operations such as driving through mountains, pulling a boat, dusty conditions, short trips, high rpm, overloading, overheating and overcooling.


Figure 2. Ring Wear

Any abrasive particles equal to or larger than the oil film thickness will cause wear. Filters are necessary to keep contaminants small. The other side of the equation is oil film thickness. Thicker oil films can accommodate larger contaminants.

Temperature has a big effect on viscosity and film thickness. As a point of reference, one SAE grade increase in viscosity is necessary to overcome the influence of a 20°F increase in engine temperature. At a given reference point, there is approximately a 20°F. difference between viscosity grades SAE 30, 40 and 50. SAE 20 is somewhat closer to 30 than the other jumps, because SAE 30 must be 30°F higher than SAE 20 to be roughly the equivalent viscosity.

In other words, an SAE 20 at 190°F is about the same kinematic viscosity as an SAE 30 at 220°F, which is about the same viscosity as an SAE 40 at 240°F. This approximation works well in the 190°F to 260°F temperature range. One might be surprised at the slight amount of difference between straight viscosity vs. multiviscosity oils with the same back number (for example, SAE 30, SAE 5W-30, and SAE 10W-30).

If an SAE 50 oil at 260°F is as thin as an SAE 20 oil at 190°F, imagine how thin the oil film becomes when you are using an SAE 5W-20 and your engine overheats. When an engine overheats, the oil film becomes dangerously thin and can rupture."

Yeah I realize this is talking about cars but I don't think it can be argued that wouldn't apply to motorcycles as well.

 

[ZeeOSix]

Originally Posted by BusyLittleShop
Originally Posted by ZeeOSix
Blackstone doesn't really know much about tribology.

Mercy Zee... to be fair did you ask them if they know about tribology???


Based on their statement - red parts highlighted - it's pretty evident they don't know much about tribology.

Originally Posted by BusyLittleShop
Originally Posted by ZeeOSix
What's their definition of "significant differences".

I gather their testing data shows no evidence of any significant mileage difference between the viscosity grades...


Post up a summary of all their motorcycle only UOAs for all to see, and specifically the UOAs from the same exact bike using a range of different oil viscosity.

 

[ZeeOSix]

Originally Posted by Bonz
"Viscosity and Wear
Thinner oils have less drag, and therefore less friction and wear. Right?


Where did that statement come from?

Less drag and less wear are not mutually inclusive. The drag they are talking about is the drag associated with the shearing of the oil when it's trapped between moving parts - the thinner the oil, the less shear drag there is. That's why all the new vehicles are using xW-20 and now xW-16 and even xW-8 to squeeze out another 0.01 MPG.

Thinner oil (or hotter oil) means less viscosity and less oil film thickness. The thinner oils rely more heavily on anti-wear additives to mitigate wear because the potential metal-to-metal contact is increased as the MOFT decreases from viscosity decrease.

The only good thing a motorcycle has going for it in terms of maintaining a better MOFT at least in the journal bearings is higher revs. The journals try to center themselves more as the engine revs increase, which increases the MOFT. Running a xW-30 in a low revving high torque output Harley wouldn't be a good idea for instance.

 

[Bonz]

The opening part of the quote simply was to put the question out there to consider that thinner oils work in most normal engine operating situations, but there are situations where thinner oils under stress may not provide the protection and that could lead to MOFT issues at higher temperatures under load, pulling a trailer etc.

The two main points in what I quoted was a heavier oil maintains a thicker film which makes sense that it would contain contaminants "within" the oil film instead of the contaminants potentially being larger than the thickness of the film. The other point is oils thin down at much higher temperatures and if the engine is at much higher temperature it thins down below what could provide the best MOFT for protection.

That all came from Amsoil oil as a relates to promoting their 0w30.

Definitely not saying Amsoil s the end-all and be-all oil-related information, but I do believe 20w is a CAFE induced outcome and no matter how an engine is engineered we can't take the heat out of the equation pulling a trailer or under heavy loads.

When I look at oil recommendations in other parts of the world for the exact same engines, they show all different weights as acceptable including 0w40, 5w40 in the case of my Acura TL SH-AWD but doesn't show up on the radar here in the states.

This is a motorcycle section of the forum but I think the information can be applied here as well.

IMO, we don't need to drink the Kool-Aid of lighter weight oils because they absolutely have drawbacks in some situations that would decrease engine longevity albeit well after the warranty has expired... And what manufacturer doesn't want to sell more vehicles because the engine starts to wear out sooner after warranty than it may have if it was using a different weight oil? Just a thought.

 

[ZeeOSix]

^^^ Bonz - I'm pretty much in agreement. Using xW-20 in a passenger car is somewhat equal to using xW-30 in a motorcycle IMO. Both "get the job done" in their respective use, but in both cases there will be potential for a little less protection (less MOFT) and a therefore a little more wear.

I think Honda is basically the only motorcycle manufacturer that I've heard of that recommends xW-30 in some applications. Has anyone heard of other motorcycle manufactures doing the same? I've never seen if from Suzuki, Kawasaki or Yamaha myself.

 

[Bonz]

Zee, great analogy of Xw30 in motorcycles is similar to xw20 in cars. And 7500 mile oil change intervals and longer are the norm with many new motorcycles these days. Transmissions haven't changed, they still shear oil. I can only imagine how chunky the gearbox feels approaching that mileage when you start with a 10w30.

Believe it or not my 1980 Yamaha XS1100 recommended 10w30 for sustained temperatures below 59° degrees Fahrenheit, and 20w40 for anything above 41° Fahrenheit.

But it was very clear with the delineation at 59° Fahrenheit you would not run that oil in the hot summer months.