How to understand this oil chart?

[ToothPick]

I am going to do a front differential fluid change on my base 2011 Subaru Impreza AT. My automatic model has separate compartments for the front diff and the auto transmission.

I need help reading this chart that says which viscosity oil to put in the front differential for the auto model. I looked at it, but have no idea what type of oil to get.

Does it say that I need "90" gear oil? It seems like there are some other letters that I should put in there to find this oil in a Google search.

Help me figure out what gear oil I need please.

 

[fdcg27]

It looks like Subaru thinks an 85W would be suitable for your climate range, while a 75W-90 would be ideal for all climates.
Just buy a couple of quarts of M1 75W-90 and you'll be set.

 

[ToothPick]

So basically any type of oil that the chart lists will do, but each oil type has its operating temperature range?

Therefore for the oil to work good at all times, both hot or cold, I should go with the 75W-90, which can work in all temperatures?

But any of the other types listed will also work in this car, as long as I use them within the given temperature range?

 

[Rand]

you need aprox 2.1qt but 2 will probably work.

1.3 for the front and .8 for the rear.

75w90 GL-5 gear oil is what you need
and since the transmission doesnt share it ..

you can be much less picky about which you use vs

a MT equipped with a shared front sump.

 

[Hollow]

For your AT Subaru you'll want a GL-5 rated 75w90 or 80w90.


I've had Valvoline Durablend semi-syn 80w90 in my Outback for about 30k miles, no issues. Getting ready to put in Mobil 1 75w90, as I found it at a good price.

 

[Tegger]

Originally Posted By: ToothPick
but each oil type has its operating temperature range?

I'm not sure what you're meaning by "operating temperature range", but that chart's thermometer indicates ambient temperature. Ambient temperature is the number you see on the thermometer that's just outside your kitchen window.

In a nutshell, here's what that chart says:
-- Does it get below freezing where you live? If YES, then you cannot use 90W.
-- Does it get above 85 where you live? If YES, then you cannot use 80W.
-- If it never gets down to -20F where you live, then you can use 85W.
-- You can use 75W-90 no matter where you live.

I'd recommend 75W-90 for reasons of simplicity. It will feel and pour pretty much exactly like motor oil, but it's not the same as motor oil.

 

[y_p_w]

Originally Posted By: Tegger
I'd recommend 75W-90 for reasons of simplicity. It will feel and pour pretty much exactly like motor oil, but it's not the same as motor oil.

It's approximately equivalent to 10W-40 viscosity, although there's a lot of allowable variation. I specifically remember motor oil being used for Honda manual transmissions before they shifted to their proprietary manual transmission fluid. Red Line says their MT-90 is a 75W-90 gear oil that's close to a 5W-40 or 10W-40 motor oil in viscosity. This is the viscosity range chart:

Now I'd recommend 75W-90 simply on the basis that you'll find it at every single auto supply store or Wal-Mart. That, and maybe 85W-140.

 

[Tegger]

Originally Posted By: y_p_w
I specifically remember motor oil being used for Honda manual transmissions before they shifted to their proprietary manual transmission fluid.

Your memory is correct.

Honda stopped specifying 10W-30 motor oil for their manual transmissions about 1994/1995, when ZDDP levels were reduced in anticipation of OBD-II.

(Speaking of memory, are you the same y_p_w who used to post to Usenet back when he was in university?)

 

[y_p_w]

Originally Posted By: Tegger
Originally Posted By: y_p_w
I specifically remember motor oil being used for Honda manual transmissions before they shifted to their proprietary manual transmission fluid.

Your memory is correct.

Honda stopped specifying 10W-30 motor oil for their manual transmissions about 1994/1995, when ZDDP levels were reduced in anticipation of OBD-II.

(Speaking of memory, are you the same y_p_w who used to post to Usenet back when he was in university?)


I had a '95 Integra GS-R and it definitely spec'ed 10W-30 motor oil for the transmission.

And yeah - that's me. However, I didn't discover Usenet until after I was out of college. Most Usenet groups are way dead even if they're not buried.

 

[mark pruett]

Originally Posted By: ToothPick
So basically any type of oil that the chart lists will do, but each oil type has its operating temperature range?


What you do is find your expected high and low temps on that chart and look down vertically and see which viscosities intersect both lines.

In my case (Dallas, TX) the lowest temp I've seen in the past 14 years is about 9F, and the highest is 112F, so I can rule out 80W because it doesn't intersect the 112 line.

You can't go wrong in this case with a 75W-90 gear oil- it's good for the entire range of temps you're likely to see anywhere in the world.

 

[Ken2]

In addition, the 75W-90 will have slightly less drag when cold for very slightly better fuel consumption.

 

[artificialist]

SAE90 is difficult to find and isn't needed. Numerous Japanese cars and trucks call for SAE90 gear oil, and I use 80w90 conventional or 75w90 synthetic, whichever is in the shop supply room. It never was a problem.

I would recommend 75w90 synthetic in your case because according to your manual, it is good at all temperatures on that chart.