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Discussion Starter · #1 ·
I just put in a zz4 350 GM crate and I've heard 10-40 is a great wt for summer and winter rather than 10/30. My buddy says he uses 20/50 for better summer thickness. Pennzoil who I called say 10/40 also is a good choice. I just broken the engine in at 500 mi and I am going to change it this weekend ...want to know other people's thoughts.
Johnny
 

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Ran 10/30 in this one, the families 64 chevelle, 69 Malibu, 78 nova...
 

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Discussion Starter · #9 ·
Well certaintly didnt make my choices any easier! some use 20/50 and some 10/30/40 and 5/30....I had been using Joe Gibbs 20/50 racing oil in my 350 engine. Guess I'll toss a coin :hmmmm2:
 

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Let me see if I can help you make the call.

Engines with tight clearances like thinner oil. 5W30, etc. Thinner oil also reduces friction. A good thing. 5W30 is a common recommendation for new cars and trucks today.

Engines with looser clearances like thicker oil. When you make a lot of power, thicker oil is also good. Thicker oil is also good to reduce oil consumption when clearances are looser or the engine is worn out.

Here's what I think:
1. A stock 50s/60s engine is going to like 10W30, straight 30, or if it's worn, 20W50.
2. An "old school" performance engine is going to like the same as 1. above.
3. A modern stock engine is going to like 5W30. Even a performance engine.
4. Your ZZ4 probably is going to like 5W30, but if it has any tendency to consume oil, a thicker oil will help.

I am guessing that GM recommends 5W30 in a ZZ4, but 10W30 won't hurt it.
 

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ZDDP

One should never rule out the possibility that the people who designed the engine knew what they were doing. :)
I agree, to a point. Those of us still running flat tappet camshafts may not be able to purchase the same recipe oil off-the-shelf that was available 30 to 58 years ago when these engines were designed. The oil companies took out the majority of the zinc a while back, due to roller lifters being pretty much standard. Bad juju for flat tappet cams.


In the old Chevy, I use Valvoline VR-1 10W-30 because Napa stocks it, it has extra zinc, and the price is reasonable.


More good oil info here. http://www.bobistheoilguy.com/motor-oil-101/ 10 chapters. After reading this article, I began using 5W-30 year round on the daily drivers. Cold starts are hard on engines, and 5W eases that to a degree.
 

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Use Valvoline VR-1 Racing for same reasons in 327/300 in my '57. I think 20-50 is the better viscosity to use here in SoCal since engines suffer more here from heat than from cold.
I too use VR-1 20-50 Racing Oil for the zddp content in my '55 Nomad that has a '68 327 bored 30 over ,268H Comp Cam, 1.52 Roller Rockers, Dbl springs.7178 large journal mains. Unfortunately with leaky valve stem seals. It puffs a small cloud of smoke at start up and at 80 mph you can sorta see a bit of smoke behind. I guess i'll have to keep her below that speed and keep adding that $6 a quart oil until winter comes to fix it.:sign0020:
 
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