Front and Rear Differential Fluid – 2007 Forester

[Stephen]

Hello all! New guy here…

I recently purchased a used 07 Forester with a 5spd Manual non-turbo, 107k miles, unknown time of last front differential oil change. Checked the fluids, noticed the front diff was a little low, so I topped it off (top line). That got me thinking about the shape of the oil front and rear. So after watching the video on changing the rear diff oil from ETCG, i gave it a shot and it was super easy. The oil that came out was dirty-ish but didn’t look terrible. The magnetic nut had a healthy amount of silverish goo/sediment on it. I used Coastal Brand 75w-90. Since I did that, about 100 miles ago, I was reading about different Diff oils specifically (http://www.lastgreatroadtrip.com/wp-content/uploads/2010/11/gear-oil-comparison.pdf) which peaked my curiosity about trying out Amsoil Severe Gear oil. I was thinking about purchasing some and replacing the front diff oil with it.

So here’s the question, finally: Running a different oil in the front diff compared to the rear… bad idea, not a great idea, or you’ll likely be fine?

My gut tells me I should just suck it up and change em both at the same time (again for the rear at least).

Is the Amsoil Severe Gear REALLY that great? I’ve read that some people can really tell the difference with stock or generic gear oil vs Amsoil although I personally think that has got to be nothing but psychosomatic .

Thoughts?

Topic

[Nick Heywood]

hmm i can’t see any reason why you would have trouble just changing the front for now, and doing both next time they need doing, after all, the oil will have to be the recommended viscosity, and both diffs have different input speeds and power anyway thanks to the centre differential, I’m not an expert but i don’t believe it would do any damage, all i would do is change them both together next time when the back needs changing in other words change the front early, if this was in my Land Rover i would just do it and not worry, but as i said I’m not an expert! 🙂

[Brandon Driskill]

I agree with rocknrollnick, you have already done well by changing the gear oil in the rear diff. Change the front with the recommended spec (Amsoil if you wish). The diffs don’t connect, so it will not be an issue. When it’s time for another change, then you can put the same oil in both.

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