Fellow mu-X owner here! If you're thinking about upgrading from the standard Isuzu Genuine Motor Oil 10W-30, check out the ZIC X7 Diesel 10W-30 Fully synthetic. I used Amsoil Turbo Truck 5w40 too (10k km interval) but it's expensive for my Garage queen mux haha. Mobil Delvac1 5W-40 is good as well.
SP certified oils have better LSPI protection than SN, and SP is what Subaru requires for this generation.
I use PUP 0w20 in mine. Lots of tests and UOA show that Pennzoil Ultra Platinum is the best non-boutique oil you can buy. But honestly any top shelf oil will work. 5k km intervals are more important than brand with a turbo engine.
I have Signature in my 25. Smoothed out the engine noises quite a bit.
Do her a favor a change the oil, with Valvoline Restore and Protect or Pennzoil Ultra platinum, it will quite down a little and it would be great for the car.
Engine noise is a little, well noisy, mine is less rumbly/vibrationy after I changed my oil and used Amsoil Hybrid oil. I can’t generally feel anything when the engine kicks on now, before I could definitely feel it every time it kicked on.
I switched oil to AMSOIL signature series synthetic, from everything I read, it out performs other oils, used to use Mobil 1
Pennzoil Platinum Synthetic. My 1988 740 has near excellent compression at 245k og miles.
My biggest regret, not swapping out the shitty 0w-20 factory filled oil for some 5w-30 Amsoil, Motul, or Pennzoil Ultra platinum the moment I took it home. Don\u2019t wait till 1k miles.
Get a catch can but that mobile 1 oil you are using is for shit . Amsoil is best for mustangs and the best for that matter period it\u2019s cost but you can run it 25k
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If choosing engine oil across many manufacturers, check the part ranking. If your choice is down to two brands, the PartReview part comparisons help.
We compare engine oil across these categories:
In March 2026 on PartReview, engine oil AMSOIL were overall better than PENNZOIL.
In March 2026 on PartReview, engine oil AMSOIL were overall more popular than PENNZOIL.
By vote balance, engine oil AMSOIL surpassed PENNZOIL:
By number of reviews, engine oil AMSOIL surpassed PENNZOIL:
In March 2026, according to PartReview, engine oil AMSOIL led more car-specific ratings than PENNZOIL:
AMSOIL are chosen by owners of cars such as: Honda S2000, Toyota 4runner, and others.
Engine oil PENNZOIL have not yet taken leading positions in car-specific ratings. You can help by adding a review and specifying your car.
If this comparison didn’t fully answer your question, there are many others on PartReview.
For example, comparisons of engine oil PENNZOIL with: Mobil, Castrol, LIQUI MOLY, MOTUL, Shell, VALVOLINE, RED LINE, OEM Toyota, Mannol, RAVENOL.
Also available: comparisons of engine oil AMSOIL with: Mobil, Castrol, LIQUI MOLY, MOTUL, Shell, VALVOLINE, RED LINE, OEM Toyota, Mannol, RAVENOL.
You can also see who is better among other engine oil manufacturers: Mobil or Castrol, Mobil or LIQUI MOLY, Mobil or MOTUL, Mobil or Shell, LIQUI MOLY or Castrol.
