dannyo66

I have a 1966 GMC C1000 with the 4.1L 250 CI inline 6. What level of Zinc in the oil should I look for? What can I safely add as an additive to bring it up to the correct level of zinc. Looking at using Mobil 1 HM 10W40 or 10W30 oil. Yea I know it's not a Vette. Still looking for my dream 66 Vette.

carbster09

don't put Mobil 1 in your old truck, unless its been recently rebuild w low miles. I did that with my vette and was left with a nice outline of the oil pan on my garage floor. I ended up replacing the oil pan gaskets as well as the vlv cover ones. It will find every possible leak point. Stick with dino oil, and if you need zinc, throw in a wee bottle of ZDDP. Job done.

3X2

Add a bottle of zddp plus to your oil. I use it in both my 69 Corvette and 87 GN along with Mobil 1 10w-30.

Here's their website:
https://zddplus.com/

HeadsU.P.

I am a little skeptical about using a little bottle of zinc additive after wiping four cam lobes / lifters. Now I purchase mineral oil w/zinc already mixed in. Mobile One is a wonderful product for vehicles with modern engines or older ones with newer gaskets. Mobile One is for longivity such as 7-15 thousand miles between changes. Ask yourself how long it would take to do that in a old classic car. It makes no sense to me, to run synthetic oil in a car that gets driven 1-2,000 miles annually.
Lucas, Edelbrock, Comp Cams, Brad Penn and others all make a mineral oil with zinc for about the same price as snythetics. Lucas has a 5Qt jug w/zinc called Classic Hot Rod oil for around $31. Stick to mineral oil like what was in your car back in '66.

CanadaGrant

I run Mobil1 European Formula 0w40 in my 69 427 with a bottle of zddp. It has a slightly higher zinc content than regular M1, is great for cold starts and hot running and have never had a problem with gaskets. My idea is that if your oil is too slick for your gaskets you have a gasket problem, not an oil problem.

sunflower 1972

Here's a full synthetic oil that is for flat tappet cammed engines,
Castrol EDGE 5w-50:https://msdspds.castrol.com/bpglis/F...PXE-AA5D5S.pdf


It's what I use. And no, I've no issues with engine oil leaks.

sunflower 1972

Bob K

What about Rotella T? I run it in my off road motorcycles. It's a desiel truck oil. I will run it in my '65 and '72 when the are finished.

Bob K.

cagotzmann

I used this. Nothing bad to say about this product. Engineered for what you are looking for.

Amsoil Z-rod 10w30

http://www.amsoil.com/shop/by-produc...tic-motor-oil/

leadfoot4

STP states that their oil additive has ZDDP as one of the ingredients....

keithl1967

I've used Valvoline VR1 (non-synthetic) for years in flat tappet motors...
It comes in 20-50 and 10-30 (although the latter is getting harder and harder top come by (it's what I put in my 77 vette)...

Big2Bird

Yup. Just 6200 miles on the car last few weeks
Ran very well. I have used Valvoline in all my cars for 40 years. No issues.

midigike

Mobil recommends that no additives be used as it can ruin the chemical composition of the oil FYI. I run the 15w50 racing oil and no issues with a bone stock 327-300.

Primoz

I use this in my 71:
https://products.liqui-moly.com/mos2...-10w-40-1.html

It came recommended from Liqui Moly as it has very high anti wear additives content that replace zinc.
I talked with their representative in Germany and they recommended this oil. So far I noticed lower oil pressure with this oil as before. Before I used Castrol 10w-40 with zddp additive and it ran with quite a high oil pressure.
Quite nicely written article with many links:
https://www.liqui-moly.com/en/press/...favorites.html

Faster Rat

I had to rebuild my engine in 2009 after using regular oil. I did not know the government reduced the zinc levels in 2005. Wiped cam, stuck lifters.

Flat tappet cams need high levels of zinc and phosphorus. Use ZDDP additive in your mineral oil if it is not specifically formulated for older engines.

F4Gary

This. I also use Valvoline VR1 10w-30 High Zinc. You can order it at Autozone/O'Reilly's.

Kelly.s

I use hd diesel truck oil in my 52 mg. It has enough zinc.

Kelly

63mako

63mako

There is NO REPLACEMENT for ZDDP. A mild flat tappet sees over 200,000 PSI at the lifter/lobe interface. A high lift, fast ramp flat tappet with heavy spring running higher RPM will see double or more. ZDDP shears and, when it does deposits a layer of phosphorous at the shear point. This is a sacrificial layer. as it wears friction increases and more is deposited, It depletes. Faster in high stress engines, slower in stock types. Roller cam engines use little so need less initially. Nothing else does this and nothing else will prevent metal to metal contact at that point under those types of pressures.

Faster Rat

I put in 20W-50 VR1 High Zinc earlier this year. Found it in stock at Advance.
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Gary...​​​​​F4s were awesome. Worked on their avionics on the transit line. I was a plane captain in a Navy A4 squadron.