In the past I've owned rear wheel drive cars and this is my first Subaru. I'm going to change the front and rear differential oil on my '98 Forester. In some of my rear wheel drive cars, the manufacturer recommended adding a friction modifier for the limited slip mechanism. Is anything like that necessary with my Subaru?
Not on any forester. Most foresters don't have a LSD (some had it as an option, XS models got it, and the XT got it), however the LSD is a sealed viscous unit so no friction modifier is required. Just use a good fluid (I like mobil1, stands up pretty well and feels very smooth)
Wonderful, everyone on this board is so helpful. Every time I have a question, I always get good advice. Thanks! There is a a full synthetic oil I have been using in my vehicles for several years and will be switching the Forester over to it. I don't want to derail this thread into a brand war, so to anyone out there who might be tempted, please don't hijack this thread with links and text about this brand oil or that brand oil or anything.
Just make sure it's a 75W-90 with a GL5 rating. Since it's the diff only, any good quality synthetic will work fine. Most I've seen have prices ranging between $8 and $12 a quart. Some booteek oils cost more. Your front diffy on the auto cars will take a bit more than a full quart.