What would YOU put in it? 1955 GMC, original V8

Status
Not open for further replies.
Originally Posted By: Shark
I have a little project going on and I'm wondering what oil BITOG would suggest using. 1955 GMC with the original Pontiac 287. It has about 40,000 miles on it and runs surprisingly well, very quiet. Drives alright but needs brakes. The oil hasn't been changed in 10 years, but has hardly been run. No sludge. It does have a filter, I ordered the Wix replacements for the canister.

I thought perhaps Rotella T 15w40. I know zinc levels are important, though the stock cam is very tame.

meantruck2.jpg


Shark,

The Shell Rotella T5 Synthetic Blend 10W-30 and/or Rotella T Triple Protection 15W-40 Motor Oils would be good choices for your truck. They are formulated with higher zinc wear package that targets high temperature and high-wear surfaces where they are needed the most, while still being friendly to catalytic converters and others emission control equipment.

-The Shell Rotella Team
 
Last edited:
I restored old cars and motorcycles for a living for several decades. Now I'm. Retired and still,doing it just to keep,busy. The absolute best oil for your truck is Mobil 1 15w-50. It is specifically formulated by Mobil for older engines . I've used it in everything from million dollar original Shelby Cobra's to Jag XKE's, '66 sting ray's, to every car in the Ford lineup from 1960 to 1972. No leaks, and no oil issues of any kind. I even use it for break in after a complete engine restoration .just. Try it once , and you'll be hooked, but good.

Some people on this website have a problem putting fine synthetic oil in an old engine because it's not "worth it". They have it backwards. The old engines need the benefits of a fine synthetic oil even more than modern cars do, and they certinly worth the small added expense .

Z
 
I do have a couple very minor objections to your point. I don't like synthetic oil in a leaker or burner, due to cost. Some old vehicles leak and burn. Of course, ones that are restored are probably not in that position, so it's not a big deal. As to the viscosity of 15w-50, that's certainly not the be all and end all of viscosity choices for classic vehicles. Some of us drive substantially older vehicles in the winter, and there still are trucks of the 1955 GMC vintage running around on farm in this province. They are much better served with a 30 grade, and a 15w-XX isn't ideal in our winters.

That's one of the things I like about Defy, and, to a lesser extend, VR1. Just because a vehicle is old and one might want a little ZDDP, one shouldn't have to be relegated to a 50 grade or something in 15w-XX, especially in vehicles that never called for the grade in the first place.

A Shelby Cobra - probably a good choice. My old F-150, not so much.
wink.gif
 
I still run several engines of this vintage and all get 15w-40 Deere Plus 50 II, mainly because of simplicity as its whats used in all on my diesel applications so its always on hand.

My trucks/engines are not used during winter so cold weather operation isn't an issue. There are many good suggestions listed here, just select one within your price-point and enjoy.
 
I did fall off the 15w-50 wagon this winter. I moved back to my hometown where there actually is a winter. I tried Mobil1 0w-40 in my Mustang, I didn't notice any difference in oil pressure, hot or cold. That was a surprise. Was expecting some difference even if not significant. Back to 15w-50 for the next oil change.

No change in lap times or 1/4 mile either....

Z

PS. is there really enough pain in wallet to not put a good synthetic oil in a leaker or. Burner ? Not for me, and I'm a cheap SOB. It just pays in the long run to use the best oil and parts you can aford.
 
With the 0w-40, you obviously still had more than enough reserve pressure. For reference, my dad when he serviced a 1964 Galaxie, used only 30 grades. Granted the HTHS was probably closer to 3.5 than it is in modern PCMO 30 grades.

As for leakers/burners, it depends how much it leaks and/or burns, of course. The taxis went hundreds of thousands of miles on conventional at double the normal OCI. It would be hard to see what benefits I would have achieved from synthetic there. Longevity was obviously never a concern, and one can only extend OCIs so far, and I only wanted them to go so far. There's a value in getting under the vehicle for an oil change, since one is likely to check other things at the same time.

Under the worst conditions, my old LTD would be burning a quart per 500 miles. Back then, with synthetic still about $10 a quart, I wouldn't have been doing it.
 
Originally Posted By: addyguy
Took the time to look at the pics...awesome rig!

But I find it's set-up odd - this was in the days before GM 'shared' everything, so why does it have a Pontiac V-8 in it?

Shouldn't it have a GM industrial engine in it...like the 305 V-6??? I think someone swapped-in another V-8 after whatever was in their gave up...still a cool ride, tho!



The first GMC V6 was released with the 1960 models and continued through 1978. I know because I drove one for a month during the summer of 1989. Go here for a fascinating web site about the GMC V6 engines and especially the GMC 702 cubic inch V12!

http://www.6066gmcguy.com/EngineData.html
 
The Defy will keep for a bit. I found a jug of SM/GF-4 QSGB 5w-30 laying around, so I'll use it first, and then move onto the Defy. I still have some Comp Cams break in additive to get rid of, too.
 
Originally Posted By: dorcheat

The first GMC V6 was released with the 1960 models and continued through 1978. I know because I drove one for a month during the summer of 1989. Go here for a fascinating web site about the GMC V6 engines and especially the GMC 702 cubic inch V12!

http://www.6066gmcguy.com/EngineData.html



Man, thanks for that link, that was a great read! I learned a few things I never knew before about those engines.
 
Status
Not open for further replies.
Back
Top