I agree if there's something causing your pressure to be below normal then get that fixed. And if there's nothing wrong to begin with, increasing oil pressure is not a good thing. All that means is the oil's thicker, as in, not flowing as it should. Additives are never a good idea. In fact, the owner's manual recommends against them and I wouldn't doubt that some of them will void your warranty. If you're concerned about engine wear and durability, consider using synthetics--the engine will outlast the rest of the car.

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Eric Konarske
'01 Solar Yellow XE 3 Pk. 4x4