Subaru Maintenance
- Thread starter Charmet37
- Start date
Subaru diffs are pretty much foolproof; any 75w90 gear oil from Mobil, Valvoline, Castrol, Pennzoil, etc will be fine (stick to only big-name companies not off brands), and if you want to get fancy, you’ve got gear oils like Amsoil SVG (@Pablo!), Redline, Motul Gear 300, or HPL.
They’re not picky; I personally change the 6 Subarus I service at 50k drain & fills, but if they’ve got HPL or Amsoil in them I’m perfectly fine with 75-100k. The NA Subaru drivetrains are overbuilt IMO, and fresh fluids are just as important as the quality brand of fluid.
I’m not super familiar with the 98 OB Sport (edit this part out, I missed the manual transmission comment lol), but do yourself a favor and crawl under the car @ the transmissionmission, look up and see if it’s got the external filter on the driver side of the case. If it does, change it… you can do it without draining much fluid since it’s well above the liquid level. That one is a rock catcher but I’d still change them maybe every 3rd-4th transmission fluid drain & fill… so between 90-120k for transmission filter.
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What does the manual say?
There should only be 2?
FRONT DIFF+MT and REAR DIFF.
For the rear any 75w90 gl-5 gear oil.
For the shared sump with MT you need a gl-5 gear oil that works well with the synchros in the transmission.
Redline 75w90NS, Motul gear 300 etc.. avoid anything that says it has limited slip additive.
FRONT DIFF+MT and REAR DIFF.
For the rear any 75w90 gl-5 gear oil.
For the shared sump with MT you need a gl-5 gear oil that works well with the synchros in the transmission.
Redline 75w90NS, Motul gear 300 etc.. avoid anything that says it has limited slip additive.
Uhhh, Rand? In the MT transaxles I’m pretty sure it’s GL-4, not GL-5, isn’t it?
Motul Gear 300 and HPL for sure are compatible with both standards (very low levels of sulfur to protect bronze parts), I’m not sure about SVG.
I’ve used the Gear 300 and HPL for so long I forgot which fluid spec is which
GL5 all around.Uhhh, Rand? In the MT transaxles I’m pretty sure it’s GL-4, not GL-5, isn’t it?
Motul Gear 300 and HPL for sure are compatible with both standards (very low levels of sulfur to protect bronze parts), I’m not sure about SVG.
I’ve used the Gear 300 and HPL for so long I forgot which fluid spec is which
Let me check for a 98 but I thought they were combined sump. so gl-5 is required.
(at least on my 2011,2015, 2013 it was so)
edit:
Checked gear oil and MT is one unit.. so it needs GL-5
like I said, it’s been awhile. I originally (circa 2005) found the Gear 300 and used that since it satisfies GL-4 and 5. I don’t like needing several different fluids for several vehicles.One engine oil to keep it running, one transmission fluid to spin the driveshat(s), and one for the diffs to keep it moving.
its GL-5. My bad.
That isn't a subaru that shares the front gear oil with the transmission however
The rear can use anything.
The Transmission/front diff needs abit more special sauce or the shifting will be terrible.
GL-5 to protect the hypoid gears in the diff, yet something compatible with MT use.
Easiest to find and use is redline 75w90NS
https://www.amazon.com/Red-Line-58304-Limited-Synthetic/dp/B000CPI5Y6?th=1
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If you mean the 17, it does share. Much harder in the front diff than the rear over the 207k on the car so far. I believe the 19 2.5 is the same arrangement but a lower torque CVT. If you meant the 98 I am not up on that one!
Motul Gear 300 for a 5 pack is $80 on Amazon quite frequently. It's what I used in my WRX.
https://www.amazon.com/Motul-105777...&sprefix=motul+gear+300,automotive,114&sr=1-4
https://www.amazon.com/Motul-105777...&sprefix=motul+gear+300,automotive,114&sr=1-4
FCP stocks Gear 300: https://www.fcpeuro.com/products/75w90-synthetic-gear-oil-1-liter-100118
Free replacement and covers all my diffs that require GL-5 and/or no slip additive. Plus it's the only fluid Wavetrac warranties. Really hard to beat from a wear/cost/coverage perspective.
Free replacement and covers all my diffs that require GL-5 and/or no slip additive. Plus it's the only fluid Wavetrac warranties. Really hard to beat from a wear/cost/coverage perspective.
A late 90's Subaru with intact rear wheelwells? I don't think I've seen that since those came out new around here!
I'm confused now is your 17 a Stick shift? if not it uses CVT fluid and is separate from the front diff.
So I think you are talking about something diff-erent
than I was.the 98 the OP has ... has a combined front diff/MT that shares gear oil.
Sorry if Im a slow one here.... How can you have free replacement on Gear oil?
Their lifetime replacement guarantee includes oil. You buy it again, submit a replacement, send back the old oil containers full of oil, they give you a credit for the cost of the oil. It's intended for european cars but no one's stopping you from ordering fluids for a Subaru.
