75W-90 vs 80W-90 in a 2012 R1200 GS

[2manybikes]

I started a few years ago trying to reduce the number of different oils and fluids for my cars and bikes. So far, I can use 80W-90 in all of my bikes with a final and or middle drive. The GS calls for 75W-90. Since Im not a mechanic, I am going to ask if the 80W-90 is OK to use.  Thanks in advance for any assistance. 

[dirtrider]

10 hours ago, 2manybikes said:

I started a few years ago trying to reduce the number of different oils and fluids for my cars and bikes. So far, I can use 80W-90 in all of my bikes with a final and or middle drive. The GS calls for 75W-90. Since Im not a mechanic, I am going to ask if the 80W-90 is OK to use.  Thanks in advance for any assistance. 

Morning  2manybikes

 

It would probably work but not worth the risk. If BMW thought that 80W-90 was OK then that would be in the specifications.

 

As a rule  most 80W-90 is conventional gear oil (not synthetic) 

 

As a rule  most 75W-90 is synthetic gear oil (not conventional) 

 

[Camhead64]

The "W" is the "Winter" equivalent weight when the oil is cold, in the case of gear oil this is measured at 0 degrees F, both your oils are 90 weight at operating temperature. Question is what range do you ride and is the lower temperature protection necessary?

[dirtrider]

2 hours ago, NewportCycle said:

The "W" is the "Winter" equivalent weight when the oil is cold, in the case of gear oil this is measured at 0 degrees F, both your oils are 90 weight at operating temperature. Question is what range do you ride and is the lower temperature protection necessary?

Afternoon  NewportCycle

 

I do believe the most single weight vehicle gear lubes are tested at 100°c (212°f).

 

And most multi-weight gear lubes are tested at both  40C (104°f)  & 100°c (212°f).

[Alan in BC]

Another possible consideration - I would avoid any gear oils which state that they can be used in "limited slip" applications, since they contain friction modifiers.

[Dave_in_TX]

On 6/23/2022 at 4:46 PM, dirtrider said:

Afternoon  NewportCycle

 

I do believe the most single weight vehicle gear lubes are tested at 100°c (212°f).

 

And most multi-weight gear lubes are tested at both  40C (104°f)  & 100°c (212°f).

Gear oil viscosity grades are measured st a lower temperature than motor oi. Motor oil is measured at 212 F.

[dirtrider]

7 minutes ago, Dave_in_TX said:

Gear oil viscosity grades are measured st a lower temperature than motor oi. Motor oil is measured at 212 F.

Afternoon Dave_in_TX

 

So what is that lower temperature used for gear oil measurement?  

 

 

[Dave_in_TX]

6 hours ago, dirtrider said:

Afternoon Dave_in_TX

 

So what is that lower temperature used for gear oil measurement?  

 

 

Look at the relative viscosity chart at https://www.google.com/search?as_q=Oil+viscosity+chart&as_epq=&as_oq=&as_eq=&as_nlo=&as_nhi=&lr=&cr=&as_qdr=all&as_sitesearch=&as_occt=any&safe=images&as_filetype=&tbs=#imgrc=u6ESC2dm4R4u0M

 

I have been unable to find that temperature so maybe I phrased it wrong but I have seen it explained that way elsewhere.

 

My main point was that a gear oil of grade X is not the same viscosity as 

a motor oil of grade X.

 

For example, 90 weight gear oil is actually about the same viscosity 50 weight motor oil.

[dirtrider]

27 minutes ago, Dave_in_TX said:

Look at the relative viscosity chart at https://www.google.com/search?as_q=Oil+viscosity+chart&as_epq=&as_oq=&as_eq=&as_nlo=&as_nhi=&lr=&cr=&as_qdr=all&as_sitesearch=&as_occt=any&safe=images&as_filetype=&tbs=#imgrc=u6ESC2dm4R4u0M

 

I have been unable to find that temperature so maybe I phrased it wrong but I have seen it explained that way elsewhere.

 

My .ain point was that a gear oil of grade X is not the same viscosity as 

a motor oil of grade X.

 

For example, 90 weight gear oil is actually about the same viscosity 50 weight motor oil.

Afternoon  Dave_in_TX

 

OK, that makes more sense as motor oil vs gear oil do use a different SAE test as well as different viscosity ranges per cSt  (not directly comparable)

 

____SAE Engine Oil vs  SAE Gear Oil_____

 

10w thru mid range of 20w  =  75w

 

Mid 20w thru mid 30w  =  80w

 

Mid 30w thru low 40w  =  85w

 

Low 40w thru 50w  =  90w

 

60w up  =  140w

 

The above is just a rough comparison as there is no direct comparison that I know of. 

 

[Dave_in_TX]

10 hours ago, Alan in BC said:

Another possible consideration - I would avoid any gear oils which state that they can be used in "limited slip" applications, since they contain friction modifiers.

Yes, they contain unneeded additives, but are the LS  additives harmful in non LS applicstions?

 

Mobil claims their 75w90 LS can be used for both applications.

[Camhead64]

On 6/23/2022 at 5:46 PM, dirtrider said:

Afternoon  NewportCycle

 

I do believe the most single weight vehicle gear lubes are tested at 100°c (212°f).

 

And most multi-weight gear lubes are tested at both  40C (104°f)  & 100°c (212°f).

Quite correct, my bad.

[dirtrider]

13 hours ago, Dave_in_TX said:

Yes, they contain unneeded additives, but are the LS  additives harmful in non LS applicstions?

 

Mobil claims their 75w90 LS can be used for both applications.

Morning  Dave_in_TX

 

"Mobil claims their 75w90 LS can be used for both applications"--- And BMW claims that they have no final drive failures. 

 

If BMW wanted either LS or non-LS gear oils used then their gear oil specification in the manual would include that information.

 

Can an LS gear oil be used  (you will probably have to ask BMW on this). 

 

An LS (limited slip)  gear oil could be used as it won't eat a hole in the alloy housing, or cause excess wear on the ring & pinion, or harm the bearings. 

 

LS gear oil's claim to fame is it's friction modifiers (to prevent clutch chatter when going around corners or tight turns), this by itself isn't a problem as the BMW motorcycle has no differential therefore it can't have limited slip clutches. The slight problem is in the second part of LS gear oil, that is it's ability to wick in between tightly spring loaded limited slip clutch plates. One of the reasons that limited slip clutches chatter is that normal (non LS) gear oil just can't get in between the clutch plates to lubricate them enough. 

 

In the old days (before specific LS gear oil) we would add a special limited slip additive to limited slip vehicle differentials to prevent clutch chatter when cornering, in most cases that was derived from Sperm Whale oil. To this day that is probably the best penetrating oil I have ever used. Due the protection of  Sperm Whales it hasn't been available for many years now.

 

If you are old enough to go back as far as the old GM in-line 6 cylinder engines, those had a habit of the  rocker arms wearing (polishing) the rocker arm balls so smooth that lubricating engine oil could not get into the pivot area so they would start squeaking.  No oil (not even uplevel high additive engine oil) could get in that tight rocker arm to ball joint & stop the squeaking. 

 

But with the engine running, if 1/2 of a very small bottle of  limited slip Sperm Whale oil additive was added to the engine oil through the oil filler that squeaking would stop within a very short time (darn near magic).

 

The above is kind of a long winded way of saying that LS gear oil is more apt to cause final drive seal seepage. Not that it WILL but that it could.