Oil viscosity.

[audiomick]

Sorry about starting another oil thread, but I have tried several times to get a definite answer to this question, and no-one ever seems willing to confirm or refute it. So I'll try it here too...

The background is, more or less, that I would like to be able to use the same grade of oil for all of my bikes. Specifically, a 10W-60.

The question is:

Is it true that one can extend the viscosity range below and above that which is recommended with impunity?

That is to say, if a 20W-50 were stipulated, a 10W-50 or a 20W-60 or a 10W-60 would all be ok, but a 20W-40 or a 30W-50 (if it existed...) wouldn't.

 

As I said, I have posed the question several times on various German forums. I got answers like "use this oil", or "using a too thin oil will destroy the motor", but never a straight up yes or no answer to the question. Is anyone game to make a statement?

[GuzziMoto]

In my opinion, which is worth what you paid for it, there is some wiggle room on oil viscosity but only within reason. And that wiggle room is affected by the environment the motor is running in (warmer climate vs colder climate) That is why on many oil recommendation sheets they list more then 1 oil viscosity, depending on temperature it is being operated in. I am not sure I would run a 10w-60 in our V11. But I doubt it would be a problem, especially once it has a fair amount of miles on it. I would not use it because I am not a fan of 10w-60 oils, they are in essence a 10 weight oil with a lot of viscosity modifiers added, and those tend to break down faster. I would rather use an oil that doesn't rely as much on viscosity modifiers. But that is really just my personal preference. If you are already running 10w-60 oils you are probably fine with it.

Also, for the Griso 1100 it started with calling for 5w-40 and at some point later they changed the oil spec to 10w-60 as I recall. I really don't think anything changed. 

[p6x]

As GuzziMoto stated, the larger the range covered, the more additives are required.

The viscosity is tested according to ASTM D445 at two different temperatures. 40 degC and 100 degC. There is a third measure at 150 degC, High Temperature High Shear.

Compare your 10W60 performance with less spread viscosities to find out how large the difference is, if any....

I am old enough to have used different oils between winter and summer. Before oils became multigrade.

As long as your oil is JASO MA2 (2023), API SP certified, you are in the clear.

I had a heart-to-heart discussion with the US Motul representative last year, when we had temperatures above 115 degF / 46 degC.

I learned that any oil brand gets their oil base from the same 5 major oil companies, and their additives from the same 5 companies worldwide.

The main difference resides in the recipe used.

His new recommendation for my V11 is this: https://www.motul.com/en-US/lubricants/recommendations/49352

But I am a long time Motul user, starting from the 70's with Motul Century 2 strokes.

Out of curiosity, why do you need 60?

[audiomick]

12 minutes ago, p6x said:

Out of curiosity, why do you need 60?

One of the bikes is a Breva 750 ie. The specifactions that I have found for it are also contradictory, same as what I have been able to find for the V11 and the V35 Imola, but one of them is 10W-60.

The valve-train on the small-blocks has a fairly hard time of it, and needs a heavy oil. At the other end, I ride in winter, sometimes at temperatures below zero. For that, I'm interested in oil that does it's job with a minimum of warming up.

10W-60 should cover everthing I have, as far as I understand it.

[Lucky Phil]

You can largely disregard the lower number in so far as you should aim for the lowest possible for a Full Synthetic group 4 oil. The "it's too thin" thing is the opinion of people with no idea about oil. To get this point straight in you head and a perspective on it think of it this way. A 0W-40 oil is still a LOT more viscous at room temperature (so the 0 end of the scale) than it is at 100deg C ( the 40 end of the scale) or engine operating temp where the engine is designed to produce maximum rated load and power and the oil is designed to provide lubrication and cooling so how can a 0W oil be "too thin"? Answer, it isn't. It's true that the wider the spread of viscosity even in a Fully synthetic group 4 oil the greater the additives with regards to maintaining the VI but it's nothing compared to older mineral based oils which always started with a higher viscosity base oil to provide a safety floor viscosity wise for those that don't change their oil. I run my Daytona engine on 10W-60 for two reqasons, one because "some" of these engines have oil pressure issues at idle in traffic at high ambient temps. It's just a little headroom for these conditions here. The second is because it has higher zink levels for the flat tappet lifters. Should it be changed more regularly than a 10W-40 oil, probably. Like you I wanted to use a single oil in all my vehicles and I chose Mobil1 0W-40 and used it for years in everything including in my V11 Sport with the original 2 valve engine. Worked perfectly and didn't have any issues with oil in the airbox etc or OP light at idle. The SP rating is the latest spec but not relevant to our bikes because like the interim SN+ which was a fill in spec until the SP grading was released these latest 2 specs are primarily about protecting direct injection engines from LSPI nothing more. Grisos went to a 10W-60 oil ostensibly to help out with oil temp issues in the oil cooling galleries around the exhaust ports these engines use but I never saw the sense in this. I've never been able to find any data on the difference between a 60 weight oils ability to absorb and carry away heat over the capacity in the same circumstances as 40 weight but I can say for sure that a 60 weight would not flow as well as a 40 weight oil in those conditions and when you are trying to carry away heat from a hot source what you want is more flow not less from a heavier weight oil. I've spoken to powerplant engineers in aviation and at GM personally that had almost no detailed knowledge about engine oils believe it or not. I wouldn't be surprised if Guzzi wasn't pretty much the same. 

BTW I've never considered using Motul oils because they don't release a detailed enough TDS listing zink levels and anti wear, anti oxidation and detergent information. 

Phil

[audiomick]

11 minutes ago, Lucky Phil said:

 I chose Mobil1

nothing to do with this, of course...

No, only taking the piss. Thanks for the explanation.

[docc]

Yak fat proponents, step ye forth!

[docc]

54 minutes ago, docc said:

Yak fat proponents, step ye forth!

Alright, sorry about the stab at humor.  

Richard Widman's air-cooled engine (Corvair) discussion is still, IMCO, worth sharing. Sure, this input still requires some "extrapolation" to apply to our V11, but ever relevant for air cooled motors. I remain a devotée to Group 5 base oil in the 20W-50 range in my original Moto Guzzi specifications.

https://www.widman.biz/uploads/Corvair_oil.pdf

[Weegie]

Having conducted various science experiments with my HiCam engine, I was going to post but been beaten to it by some great info from previous posters, @Lucky Phil has already said more than I could add (and like him I run a 10/60 in my HiCam)

Anectodally, I run 15/50s in my Sporti and I've never had any issues with the 2v/v engines.

Now I always check the spec sheets, I was surprised by the viscosity differences from supppliers selling, what appears to be a similar product. All full synth group 4s at a given grades can vary quite a lot in their viscosities and viscosity index.

That's all I have to add

[activpop]

In my older bevel drive Ducatis and Beemer, I always ran 10/40 winter and 20/50 summer. Now I do the same on the Guzzis. I'll look into this 60 weight stuff more, but I have time. Warm weather isn't here yet.