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TR2/3/3A Adding STP to Castrol 20W50 oil?


Obi Wan
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I'm not a fan of any oil additives. Oil is formulated with great care, and anything it needs is already there. Get a good quality, name-brand oil and it will have everything you need.

There are loads of stories of oil additives damaging engines.


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The TR6 holds about 5 and 1/2 quarts...of that is 8 oz of STP...I just like the way it makes the Valvoline or Kendall 20w-50 feel a little more slippery.


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I used to use it in my old cars with tired engines to bring oil pressure up. It seems like it would add 5-10 pounds for a while then would break down or whatever and I would be back where I started.

I have decided if you need a rebuild you aren't going to find it in a can.

If your engine is in good shape it should be fine with regular 20w-50.

Either way don't see a good case for using it.

Years ago I used a mixture of STP and motor oil to "upgrade" my lever shocks, which were wearing out. That actually seemed to work pretty well.

Greg Lemon
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