The Stovebolt Site Forums The Shop Area Engine Shop What oil to use in '50 GMC 100 pickup??

ve got myself an owners manual for my '50 g,c shortbed with its 228 motor and i'm hesitant to go changing the oil until i get a knowledgable recommendation from a few of you guys as to what would suit it best? I was looking into a straight 30 weight here in PA with temps now at 60 - 72 degrees. engine has 184,000 miles on it and after getting it to start up today i notived it sounded like it needed oil bad! no clunking just sounded like it was working a bit hard,..hard to explain really! if you're really interested in hearing it email me i'll get you my ph# and you can listen to the sucker,...lol!

Thanks in advance!!

If the oil has been in a long time drain and refill with 30W and 1 qt of auto trans fluid (has a high detergent). Run easy for 200-300 miles, drain and replace with 10W 40 for an engine that old in that climate. (I use Valvoline High Mileage) In the summer a quart of Lucas additive wouldn't hurt. Condensation and acids in old oil will eat bearings. The trans fluid will loosen deposits in an old dirty engine.

AWSOME!!!,..that was the kidn of good solid advice i was looking for. I'd be curious to hear other recommendations out there also. curious to hear what others do aso. Thanks a million,..my truck thanks you too!! lol

Coal Town -- Please go read all of this thread before you make any decisions.

http://www.inliners.org/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=3;t=000583

Boo

Thanks Boo! Took a look at it. Sure does seem that a lot of people are using the multi weight stuff huh?? Not sure though even after reading all that what I'd be best at using. Fact is this is an engine with 184,000 miles on it and it seems like many of those engines that people were talking about on that link you gave me had newer engines?? Of course mine is a straight 6 from 1950....

worth pointing out that all oils are detergent, unless you specifically get a straight mineral oil - I think it depends on wether the engine has been run w/ or w/o a filter since new and what oil has been used in the past - if the trucks new-to-you then most likely it has been using the standard 10-30 for decades, and no reason to not stick to that in your climate for normal use - doesn't hurt to add a filter if there isn't one, but for my money the best policy is simply 10-30 w/ frequent changes and watch the oil pressure!

multigrade oils are designed to work at all temps - they act thinner when it's cold, thicker when hot - straight weight oils get too thick in the cold, thin too much when hot - if you have really hot summers then maybe 10-40 in the summer, 10-30 winter

Bill

I agree with Bill on the previous use and whether or not you have filter. It's true, these trucks were designed to run on a single weight, non-detergent oil.

Without a filter, I would run SAE 20 in the winter, SAE 30 in the summer in a non-detergent oil. The theory is that the dirt settles in the pan, then is changed hot so the sludge flows out when the oil is changed.

With a filter, I would run a multi-viscosity detergent oil, preferably 10W-30. Dirt stays suspended in the oil and is trapped in the filter. I do not like the 10W-40 oil, it has a lot more polymer in it to spread out the viscosity range. For years GM would void your warranty if you used 10W-40. I know the oil has improved, but it still has some problems.

From an engineering standpoint, running a multi-viscosity oil in an engine designed for straight oil will not cause any problems, as long as it is an oil that doesn't suffer from premature breakdown, like the 10W-40. You still have the lube quality of the higher number, but when the oil is cold it flows like the lower number due to the polymers added.

Another issue is cleaning the inside of the engine. Years of sludge buildup can cause problems, but cleaning it out can bring another issue, leaks. The big item is to keep the oil changed and to run the engine at normal operating temperature on a regular basis to keep the water boiled out of the oil, which is what causes the milky residue in the engine.

The one thing I just noticed when I started the engine was the oil pressure guage wasn't registering anything?? Would I see anything right when it is started up or would I have to wait till it runs a bit?

Also as you had mentioned Fred, should I run the engine a bit to heat things up tonight and "THEN" change the oil,..or since the engine sounds rough, just go and change it cold??


Jason

when my grandpa bought a used car he put diesel in the motor (a gallon or so) after draining the old oil and ran it warm for 5-10 min shut down and drain,put some k-mart oil in and ran again for a couple minutes nice and warm then drain and put new good quaker state oil and filter, then continued usual maintenance. ive nevr done this yet ,,,anybody have a comment/?
he also put a cap ful of tranny fluid in the gas tank every other fill? come to think about it he rarely broke anything?

I run 10W-30 in everything I own, even the lawnmowers,
Scott

My mechanic advises me to add 4 oz/ 10 gallons gas of marvel mystery oil. If you don't want to use multigrade, go with a 40 or 50 (summer useage)with that high mileage engine and the marvel will give you the lube you need at start up.

First, how long does it take for the pressure build up? Others probably know better, but I would say it needs to be up within a minute.

If you run non-detergent oil, it must be changed hot. With detergent oil, it can help, but is not a requirement. Since you don't know what's in the engine, I would do the first change hot, if possible.

Coal Town Kid!

You're getting some good advice here about oil from the guys on here.

Fred T has given a good explanation and it sure fits in with the experience I have had over the years.

Oil pressure should rise within 30 seconds--don't run the engine more than a minute without it. That 30 second rule has always been what I've been taught over the years. That may seem like a short period but if you try an experiment you'll see what I mean. People are poor judges of the passing of time! Take a stop watch and time those 30 seconds! You'll be surprised at how you would have shutdown earlier without timing it.

In the very early 50's I worked at a service station and we offered 'engine flushes' when doing an oil change. The flush consisted of 3 quarts of Varsol and one quart of #10 oil. The engine was run for about 2 minutes then that was drained and refilled with fresh oil. I can't say that was a good procedure though. We always used #30 oil in the summer and #10 in the winter. The manual for my 1946 truck says that for really cold weather you can add 10% kerosene. But that was before any of the lesser weight or multiviscosity oils.

George

george-
sounds like you've been around for a while!!?/ wish you lived around me,..i'd be borrowing you all the time!..lol! where ya from?? i'm in PA myself.

Thanks for the oil pressure info,..i'll put it to use later tonight. I forgot about my uncle's 40th birthday so that's gonna screw my day up! no wrenchin today,...will try for a nightime hang in the garage though!!