Mobil 1 75w90 in Subaru Forester

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usually anything with a LS modifier is bad, you want a specific gear oil that's GL-5 and made for use in MT's so that the synchros work properly. Redline 75w90NS or motul gear 300 are examples of good fluids surprisingly supertech 75w90 blend is "ok" as well.
 

buster

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Originally Posted By: Rand
usually anything with a LS modifier is bad, you want a specific gear oil that's GL-5 and made for use in MT's so that the synchros work properly. Redline 75w90NS or motul gear 300 are examples of good fluids surprisingly supertech 75w90 blend is "ok" as well.
cheers
 
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Subaru's own 75w-90 is now available in quarts from the dealer. It's made by Isemitsu. I've tried three different options and found that to be the best by a wide margin. I got mine from Fred Beans.
 
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Originally Posted By: Rand
usually anything with a LS modifier is bad, you want a specific gear oil that's GL-5 and made for use in MT's so that the synchros work properly. Redline 75w90NS or motul gear 300 are examples of good fluids surprisingly supertech 75w90 blend is "ok" as well.
Does it call for GL-5 in the trans? Pretty much every manual I've seen wants a GL-3 or GL-5 if it's not some sort of proprietary fluid or an ATF fluid. That being said, doesn't basically all GL-5 oils have friction modifier? I always recall reading that GL-5 fluids are not ideal for manual transmissions. Unless it actually calls for a 75w90 GL-5 oil, I wouldn't feel comfortable running the M1 in my trans if it was something that I planned on owning for awhile. Just my thoughts. On a side note, I've used a bunch of different manual trans oils over the years and had the best results in with the BG Synchro Shift II fluid. Smoother results in the different vehciles I've owned than the Redline MTL. These are 75w80 applications though. I did have one car than worked very well with the MT90, and one that the Amsoil manual trans 75w90 was better in.
 
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Yes it requires gl-5, No they don't all have a friction modifier.. at least they don't all have FM's that are bad for MT. Some are designed for good synchro operation. However the EP additives can cause shift quality to be worse than gl-4. That's why its not recommended to use gl-5 if the application doesnt call for it. I had bad luck with subaru extra S in my 2011 forester worst shift quality out of 5 or so options I tried. The 2015 spec's subaru extra MT which is a 75w80 gl-5 gear oil. Subaru does state you can use a 75w-90 gl-5, but it may have worse shifting and fuel economy. link to subaru "extra mt" gear oil spec'ed for 2014+ forester mt http://parts.subaru.com/p/Gear-Oil-Extra-MT-75W80/49506107/SOA748V0100.html
Quote:
Genuine Subaru Gear Oil Extra MT 75W-80 is uniquely formulated for Subaru manual transmissions. This low viscosity fluid reduces mixing resistance, enables efficient power transfer from engine to tires and provides improved fuel economy. It has greater oxidation stability, extended anti-wear performance and is original equipment filled at the factory. • Maximizes the performance of the Subaru manual transmission • Low viscosity for improved fuel efficiency
Something is working 600miles on the 2015 and its already at 29.5mpg average 32+ on highway.. and that's not really driving for economy.. 75 on highway etc. the 2011 forester topped out at about 31 max with the factory tires more like 28.5 with the kumho 4x.
Originally Posted By: Johnny248
Does it call for GL-5 in the trans? Pretty much every manual I've seen wants a GL-3 or GL-5 if it's not some sort of proprietary fluid or an ATF fluid. That being said, doesn't basically all GL-5 oils have friction modifier? I always recall reading that GL-5 fluids are not ideal for manual transmissions. Unless it actually calls for a 75w90 GL-5 oil, I wouldn't feel comfortable running the M1 in my trans if it was something that I planned on owning for awhile. Just my thoughts. On a side note, I've used a bunch of different manual trans oils over the years and had the best results in with the BG Synchro Shift II fluid. Smoother results in the different vehciles I've owned than the Redline MTL. These are 75w80 applications though. I did have one car than worked very well with the MT90, and one that the Amsoil manual trans 75w90 was better in.
 
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buster

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What do you mean by ...and it seems the LS oil is not recommended in ...? What is recommended, by the manufacturer, for your car? Is LS oil prohibited? Are there explicit warnings from the manufacturer of your vehicle or the oil that prohibit the use of M1 75W09LS in your car? While I haven't read all Subaru manual transmission and differential gear oil specs, from what I have seen so far, they usually simply spec GL-5 and 75W90. (Although starting in '14, there is a new Subaru gear oil, Extra-MT that is 75W-80.) NO WARNINGS OR ADVISORIES REGARDING LS. The cars that have the plate-clutch differentials might have specific requirements regarding LS oil, I haven't seen an actual spec for this application. I used M1 75W90LS in my '08 Subaru 5MT and rear diff, and it was fantastic. That car shifted beautifully from the time I added the oil to when I sold it, some 66,000 miles on the same oil. I recently changed to Mobil DELVAC gear oil in my '12 5MT and '14 6MT because the DELVAC is supposed to be the heavy-duty version of M1, and I have plenty of experience with the DELVAC product line from running my diesels. The '12 5MT and '14 6MT are loving the DELVAC.
 

buster

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The M1 is not ideal as there are better fluids but it does work. I haven't noticed any problems yet. I'll report back after a few hundred miles.
 
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UOA it. Besides the Motul and RedLine, other nonLSD gear fluids are Eneos, Oreillyauto Masterpro, Wynns, BG, Amsoil FGR longlife, Neo, Torco, Ford QGT,... Delvac already mentioned but many overtheroad trucker GL5 gear lubes are nonLSD. Toyota/Honda have nonLSD GL5 75w85 if you want to try thinner for better shift quality. You should research the lsd additive's effects on viscosity, oxidation, corrosion, moisture...
 
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