Since Amsoil has been mentioned, thought I would flap my gums on my perception of the product.
I have never used Amsoil and I personally know no one who has. It's probably a reputable company with a fine product. But to my mind it seems to be advertised and multi-level marketed in a "snake-oilish" manner. Correct me if I am wrong, but this is the perception I walk away with from viewing websites selling the product.
Joe
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'67 Chevy C20 fleetside, 250 inline, 3 on tree, heavy duty clutch and brakes, heater, steel bed floor
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"Tighten until the stud snaps, then back off half a turn."
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