[2013GV]

Better technology, oils have improved, especially the multi grades.

The biggest thing is the ambient temperature in your area.

select your oil based on the temperature range you experience, here i experience-10C to 30C and I use a 75W90 in the gearbox and an 80W90 in the transfer and differentials. I find the 80W90 just a little thick in winter while the gearbox is cold. Personal preference and probably no lubrication issues just a nicer felling when shifting is the only reason I don't use a heavier oil

 

[016]

Then I make sure to change according to the latest recommendations.
Since I live in Sweden, there is great variation in the temperature. (-25 to +30)

 

[2013GV]

75w90 GL4 gearbox, 80W90 GL5 for diffs should cover that temperature range

 

[016]

Although the viscosity is subjective, keep in mind there are YELLOW metals in the transmission so make sure you use compatible fluids..

What about the transfer case? Does it need to be an oil that does not damage yellow metals?

 

[2013GV]

GL4 in transfer, same as gearbox

 

[016]

🤔 This makes me confused ... again :

 

[Max]

Me too!

 

[2013GV]

I run gl4 in my transfer, but looking at the fsm, theres only 2 bushes in there as sliding bearing surfaces, not under pressure like a syncro cone would be in a manual box which is where the issues arrive using a gl5 .

Based on that, there should be no reason you can't use a gl5 in the transfer case.
If your gl5 oil is listed as yellow metal safe, id use it.

 

[fordem]

Thank you for the answers.

I feel a little confused ...
Does anyone know why different oils are recommended depending on which year the car was manufactured?

Did they make such big improvements or have they just discovered that other oils work better?

In recent years more governments have mandated "better" fuel economy numbers, lighter (lower viscosity) oils is one of the ways manufacturers are meeting these mandates, lighter oils reduce drag, as well as protection, but, as long as it gets you through the warranty period ...

 

[aquanaut20]

Different viscosity oil may be chosen to affect the EPA fuel usage, there for changing the economy of driving..

 

[*Kiwi]

What about the transfer case? Does it need to be an oil that does not damage yellow metals?

No yellow metals present in transfer case. My guess, as already mentioned, is that it's only the tiny centre diff gears that would benefit from GL5 because they had to fit it into the same space as the earlier LSD.

🤔 This makes me confused ... again :

It shouldn't; the only discrepancy between my 2016 model year manual and your reference is the 75W-90 gearbox oil. Certainly If I was towing a substantial load I'd consider a 75W-90 GL4 for the gearbox and accept the poorer shift quality.