original motor-best oil type
 

time to change the oil in my 50' gmc 228 its original with 63,ooo miles a valve job runs sweet with some blow by . if you you guys got some suggestions on wieght or synthetic or non that would be great. thanks in advance!:gmc2:

Re: original motor-best oil type
 

As far as I know, you cannot use synthetic oil for the '47 - '66 generation engines. Someone correct me if I am wrong on that.
Napa sells an oil specifically designed for these engines. Not sure about the weight but that can be found out easily enough.

Re: original motor-best oil type
 

I would use a diesel oil, something like Shell 15w-40 Rotella T or
Shell Rotella T6 Full Synthetic 5W-40

Re: original motor-best oil type
 

It doesn't matter if you run synthetic or not, but the oil has to have ZDDP in it which is a zinc additive. Zinc was eliminated recently in most oils because it shorten the life of catalytic converters.

Running without zinc will destroy the valve train in a flat tappet motor.

I run synthetic in everything I own, and pretty much wouldn't run anything else.

I know back in the late 60s, early 70s, I ran Valvoline 30wt non-detergent in my '47 216, and 49 Jimmy with a 270.

The topic of oil can get pretty controversial — just make sure you have zinc.

Re: original motor-best oil type
 

Valvoline VR1 Racing oil has zinc in it and usually comes in either 10-30 or 20-50 weights. Autozone usually carries it. Another option is to use you favorite oil and just put in an additive like STP, which has zinc.

Re: original motor-best oil type
 

Good to know, thanks guys!

Re: original motor-best oil type
 

Not to hijack, but is anything different on the 55-59 235's? I haven't driven it at all since I changed it so if I need to change it out again I can, but I just went with a 5W-30 Valvoline oil mix.

What about transmission/rear-end, anything special required to accommodate the old mechanicals?