Discussion in 'Small Block Tech' started by Paul Stewart, Feb 17, 2018.
10W40 castrol GTX + zddp per oil change.
20W50 was used in the old jaguars.
Classic car club of Indiana has DA co. custom formulate oil for our cars. On the web.
The thing with just adding a bottle of zinc to newer API rated oils are you still have allot of calcium in the detergent packed within the oil.
Zddp and calcium try to do what the other doesn't want to do..
Calcium strips away thenprotection barrier while zddp puts a protection layer between metal
I think you meant to say the Calcium detergents look to clean, and the zinc (zddp) tries to cling to parts.
Yeah, ment to say calcium haha
I had this discussion on my other thread regarding the oil to use on a newly rebuilt engine.
everyone on here says to use 10/30.... but as you say, everyone over here (GB) runs the 20/50 on their classic cars... and that's what I use on all my old harleys.
I understand the 20/50 will make the oil pump work harder on start up....
tempted to go with 10/30 after I drain the break in oil...... but everytime I mention 10/30 to someone over here they say I'm crazy hahaha
Cars were built over here, we have the ultimate say.
In all honesty, its just not a good idea to run that super thick oil in ANY vehicle, unless you live in the heart of the Sahara, let alone a classic car, especially one with a oil pump like Buicks have. It is cooler over there in Europe, so you would be fine with 5w30/20 in all actuality. Just gotta have some kind of additive with zinc for long life of the cam.
Oh for crying out loud. Look at your oil pressure gauge! If after the engine is fully warm and the oil temperature is as hot as it will get (highway speeds for 20 minutes minimum), you have 10 psi/1000 RPM, then you are good. Do that with the thinnest oil that gives you those results. Let the engine tell you what it wants. I wouldn't use 20W/50 unless I had to.
I remember on the stock motor the oil pressure gauge would go to 5 lbs at idle after it was totally warm. Sometimes it looked like it was on "0" I ran it for a lot of years with it like that and I always used 10-30 oil. The 20-50 will be hard on the oil pump. If you are that concerned with it mix 3 qts of 10-30 and one 20-50 if this make you feel better.
If you want to run 20-50 oil you better let it be totally warm before you drive it and DON"T take it over 1500 rpm until it is warmed up
I'm going to follow you guys advice and go for something thinner and keep an eye on the oil pressure gauge.
i've taken some notes of what I should have on the gauges, so maybe after the 10/30 I'm using for the break in I'll go for the same grade 10/30 and try find something with zinc or just put an additive in..
Just putting a ZDDP additive in is no bueno too, as new oil has too Much calcium in the detergent package..
Here's a good short list of brands with correct ratio.
Joe Gibbs Driven HR2(coventenial) or HR4(synthetic)
Quaker State Defy(synthetic blend)
unfortunately all those brands we don't have in the UK... Life is hard on this side with the lack of parts and stuff for american cars.
I did find this one... says made in America!
it's a 10w30 with High Zinc....
oh wait!! I found that Ams oil!
is this the stuff? expensive blood for the engine! £70 for 5 quarts!
or I have this 10w40 at half the price!
penn grade 10w40 here.
That Lucas should work too