Synthetic: Use the LOWEST 1st number available ?

[lomez]

I'm only making in more complex because in addition to the HTHS #s, I'm concerned about flow...thus coverage. As we know, all the shear numbers in the world don't matter, if there's no coverage, because there's no flow, and oil is bypassing the pump. That was sort of the point I was going at, in the beginning.

So, it turns out that the HTHS for the Motul 15W50 (I'm currently running) is 5.33 That's great, but the kinematic viscosity at 100 C. is claimed 18, while viscosity at 40 C. is claimed 128. The manual calls for 10W40, and that 15W40, 20W40 and 20W50 are acceptable in summer. I wonder how a 100 C. viscosity of 14 (typical 10W40) compares, in terms of protection/coverage, to a 100 C viscosity of 18? Probably no measurable difference, except in fuel economy?

For comparison:

Mobil 1 5W40
HTHS- 3.8
100 C- 13.4
40 C- 81

Mobil 1 10W40
HTHS- 4.0
100 C Visc.- 14
40 C visc.- 82

Mobil 1 20W50
HTHS- 4.5
100 C Visc 18
40 C Visc- 125

Motul 5W40
HTHS- 4.51
100 C visc- 14
40 C Visc- 81

Mobil 1 0W50
HTHS- 4.1
Vis@100- 17
Visc@40- 100

 

[lomez]

Originally Posted By: Gokhan
Originally Posted By: lomez
The manual calls for 10W40.

I thought you said 20W-50 in your original post. If it says 10W-40, why don't you use 10W-40? There is no reason to go to higher viscosities, which will put more stress on your engine and reduce your fuel economy, unless your engine isn't working well with the recommended viscosity (oil consumption, wear problems, etc.).

A conventional 10W-40 would be just fine in your case. In Southern California you would really never need a 5W-40 or 0W-40 oil for cold starts.

You can use Rotella T6 5W-40, Delo LE 5W-40, or similar synthetics but there is really no need, unless you're trying to achieve longer oil-change intervals.

You can also experiment with fancy synthetic 0W-40/5W-40/10W-40 oils such as Amsoil, Redline, Royal Purple, etc. at your $$ expense if you like experimenting.

If you want to pick up an xW-40 out of a bunch, choose it based on HTHS. It's always a difficult compromise: larger the HTHS less the fuel economy, more stress on the engine, less protection on the piston rings, but more protection on the bearings; smaller the HTHS more the fuel economy, less stress on the engine, more protection on the piston rings, but less protection on the bearings.


Thanks. So, after this whole exercise, I think you're right, and that a good synthetic 10W40 is the way to go. It's a water cooled engine after all. Nothing more magical than that.

 

[Gokhan]

Originally Posted By: lomez
Thanks. So, after this whole exercise, I think you're right, and that a good synthetic 10W40 is the way to go. It's a water cooled engine after all. Nothing more magical than that.

Apparently with motorcycle oils, friction modifiers (too much can cause slippage) and oil shear (shears more easily than in car engines) are the only two differences from car-engine oils. 10W-40 would be an excellent viscosity choice -- with decent flow, thick enough viscosity, and little viscosity-index improvers (VIIs) that could cause problems.

You could also use a conventional 15W-40 such as Rotella T Triple protection, which has very little friction modifiers. Another popular choice among motorcyclists is the fully synthetic Rotella T6 5W-40. These heavy-duty engine oils (HDEOs) might work equally or better as motorcycle-engine oils and save you a lot of money as well. Both the Rotella T Triple Protection 15W-40 and T6 5W-40 are JASO DH-2 and MA certified for motorcycle engines. See the product data sheets: PDSs for Rotella T and T6.

You might want to check motorcycle forums on Rotella to see how the motorcycle-certified HDEOs Rotella T Triple Protection conventional 15W-40 and Rotella T6 synthetic 5W-40 do in motorcycle engines. Otherwise, try some conventional or synthetic 10W-40 motorcycle oil.

 

[CATERHAM]

Yes this post really should have been in the motorcycle forum from the get go.

 

[lomez]

Originally Posted By: CATERHAM
Yes this post really should have been in the motorcycle forum from the get go.


Why? It was an exploration of IF it is a good idea to use the lowest possible "W" for synthetic oil, assuming the recommended grade for an application.....for internal combustion, 4-stroke engines. The motorcycle just came up as an example of something I'm doing today. I could have just as easily used any of my cages too.

The bottom line, that I took away anyway, is that like always, there's more to the story than just one variable (such as spread, stability, HTHS, etc.) And like always, there are tradeoffs. I appreciate the knowledge that's been imparted, and feel like I've got a much better system for determining appropriate engine oils.

 

[Gokhan]

If I were in your situation, I would try the JASO-certified Rotella T6 5W-40. It has the recommended (xW-40) viscosity for your application, is well-respected in the motorcycle community, has the advantage of being fully synthetic, has low cold viscosity, and is the cheapest fully synthetic oil you can get for your application, also widely available.

 

[OnTheFence]

The info regarding the "real" weight of a multigrade is confusing. I took from this that:

The base weight of the oil is 5 in a 5w-30, and that there are Viscosity improvers that will (Thicken?) the oil to a 30 weight when at operating temp.

That is 180 out of phase with a lot of other info I have found. I thought the 5w-30 was a 30 weight that had additives that would allow the oil to flow like a 5 weight oil in cold temperatures.

Seems to me if #1 were the answer a multigrade in the summer would be a waste.

 

[hal2626]

Triumph recommends 15w50