[buckeye23us]

I have a 1964 GTO. I change the oil at the beginning of every driving season. I always used Castrol GTX 5W- 30 oil. At a car show I recently won a case of Castrol GTX Magnatec 5W- 20 oil (semi-synthetic oil) Can I use this or should I stick with what I have used in the past. Your input will be greatly appreciated.

Frank

[ponchjoe]

I'm not an engine builder but if you are running a real Pontiac motor and not a newer LS model NO. 5/30 5/20 are made for the newer cars where the clearances are much more controlled or even tighter. 10w30 is the lightest I would run but I use 15/w40. Everyone has an opinion but here is a good read.

https://www.google.com/amp/www.hotro...ngine-oil/amp/

[Hillard]

I personally have seen nothing but sludge from Castrol. I will not use Castrol. And I agree with ponchjoe. Do not use 5w-30 or lighter. Use 10w-40 or 15w-40.

[79Bird99]

Rotella 15-40 here, sometimes substitute Delo 400. The diesel oils still have some zinc left in them if you are still running a hydraulic flat tappet.

NO to the free oil...use it in the daily.

[Lemans64]

agree with above post, 5/20 is for newer cars. I run a 15/40 conventional in mine.

[dataway]

I voted yes when I meant to vote NO. Would never run oil that thin in an older engine.

[72LuxuryLeMansLa.]

My philosophy on oil weight is to use the lightest oil that will give you sufficient pressure at hot idle. If you use 5w-30 and have 15-20psi at hot idle you are good to go. If you go lighter and maintain pressure you are good to go.

[PunchT37]

Iv`e been running Castrol for 30yrs plus. No sludge problems.

That being said, I wouldn`t run a multi weight 20 in my `64 engine, of any make.

[Simple Man]

Pennzoil SAE30 is what I use in the 68. Straight weight is getting harder to find, though.

[64speed]

I would run a 10/30 or 10/40 from a good brand. I have never tried the amsoil products but that seems to be the latest and greatest. Royal purple is available at advance auto now and I hear it's wonderful oil. So far I've been running regular Mobil in my Yukon and Mobil 1 synthetic in my wife's 2013 charger.

[hal101]

Originally Posted by 72LuxuryLeMansLa.

My philosophy on oil weight is to use the lightest oil that will give you sufficient pressure at hot idle. If you use 5w-30 and have 15-20psi at hot idle you are good to go. If you go lighter and maintain pressure you are good to go.

i agree with this completely

[hal101]

i ran amsoil 5w-30 in my 400 firebird all the time from daily driving to 11.95@113 at the track