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Old 01-05-2022, 10:30 AM   #15
MikeB
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Join Date: Jul 2000
Location: North Texas
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Re: What oil are you using in an older flat tappet motor?

Quote:
Originally Posted by Sabaka454 View Post
Just buy a case of this and drop one in at each oil change.

https://www.stp.com/products/oil-add.../oil-treatment
It's better to buy oil with adequate levels of ZDDP so you don't overdo it with an additive, which can create other problems.

From Driven Oil: If you have too much ZDDP, you start to see corrosive wear and cause another problem. Adding an excess causes the oil to become acidic, and before you know, you’re wearing cams, bearings and bushings because of too much ZDDP.

The problem is you're flying blind if you don't know how much ZDDP is in the oil's additive package. I even recall an article by the makers of a ZDDP additive that describes how to calculate the proper amount of their product to add to a motor oil. That amount depends on how much ZDDP the oil already has.

By the way, STP is a "viscosity index modifier", in other words it thickens oil, which your engine may not need or even like. However, if you have an old engine with blow-by, low oil pressure, etc., then go for it! But I'd probably just start using 20W50 oil instead.
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Mike
1969 C10 LWB -- owned for 36 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, recent AAW wiring harness, 5-lug conversion, 1985 spindles and brakes.
1982 C10 SWB -- converted from 250-six to roller cam 350, Vortec heads -- sold
1981 C10 Silverado LWB, 305, TH350C -- sold, but wish I still had it!
1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming.
Retired as a factory automation products salesman.
Worked part-time over the years for an engine builder and a classic car repair shop.
Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then!
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