Oil type for a stock 41
 

I need to do an oil change on my wife's 41 gmc before I take it to a show on may 8th and was wondering what would be best for the stock I6. Any help is greatly appreciated.

Re: Oil type for a stock 41
 

I'm no expert on the old engines but if it were mine I'd use a straight 30 wt. Like Castrol Heavy Duty.

Re: Oil type for a stock 41
 

That was my thought, but I'm not sure if I should use detergent or non-detergent. Any thoughts?

Re: Oil type for a stock 41
 

If it does not have a oil filter I whould use non-detergent.

Re: Oil type for a stock 41
 

thanks for the heads up. I don't even know if this thing has a filter or not, I guess that's on the list for the to do list before the show.

Re: Oil type for a stock 41
 

The oil filter will be pretty obvious. If it's a Chevy it's bracketed onto to the intake manifold. If it's a GMC, it will be on the pass. side mid-block at the front. I would DEFINITELY NOT use detergent motor oil on an un-rebuilt vintage engine. Detergent oil will start to clean up the sludge and then clog your internal oil passages with that same sludge. Main bearings will be the first target. 30 or 40 weight is correct depending upon your location. Have fun at the show.

Re: Oil type for a stock 41
 

I agree on the straight weight.I`m thinking 40w for warm weather especially if the motor has miles on it.

Re: Oil type for a stock 41
 

Thanks for all the replies. The motor was rebuilt about 10-15 years ago, and has prolly only 500-600 miles on it. It was restored by my wife's grandpa and he passed away 8 years ago, since then I've only driven it twice. I started working on it today to get it in shape for the show. I charged the battery and fired it up, I must have junk in the needle valve because it is blowing black smoke and the carb is overflowing. I pulled a wheel cyl and took it to the local napa and they said that it is from a 53 chevy, so I ordered 2 complete cyl and 2 rebuild kits. So now I gotta get the brakes back together and move it from the small garage to the big garage then pull the carb, change the oil, and start cleaning.

Re: Oil type for a stock 41
 

Then in that case use the latest and greatest multiweight detergent oil you can buy. Even synthetic oil might keep new sludge to a minimum.
And you should probably do all 4 brakes completely over, not just 2.

Re: Oil type for a stock 41
 

Personally, I'd still use a straight 30 wt. in a 60+ year old engine. But I agree with K-Ten that you MUST do all four brakes.

Grandpa went to more modern Bendix brakes instead of searching for the original Huck brake parts/kits. These days you can buy parts for those from Chev's of the 40's and others but 10-15 years ago (or more) I doubt it was as easy...and I doubt if Grandpa was as internet saavy as a Grandpa (like me!) is today.