Ok, I know this subject has been hashed over many times over the years but something new just came to light and I need some input. While watching the Velocity Channel the other night the owner of FantomWorks had just restored a 1939 GM and recommended to the customer that he use 15-40 diesel motor oil. Interesting--I have a stock 1937 216 that needs an oil change--any thoughts.

Thanks

From what I recall a few years ago, they were taking additives that used I believe zinc out of most motor oils. I understand it was harmful to catalytic converters. So at the time it was believed that the 15W40 oil for diesel motors still had the additives. Well I think that all has changed. Some folks like to have a heavier oil in the old motors hence the 40 rating.

Put 10/30 in it. thats what I put in my 37 and 52.

I have been using Shell Rotella 15/40 in everything from my old cars to the lawn mowers with excellent success. It is in my 28, 31, 36, 36, all stock engines, as well as in my 29 4 letter brand name car. Just my take on it. By the way, Shell Rotella is a Diesel Engine Oil.

There is still zinc in modern oils; The amount has beeen r4educed. At one time, like 10 to 15 years ago, oils contained 1200 to 1400 parts of zinc per million. It has been reduced to 800 PPM. This is more than sufficent for pre 1962 4 and 6 Cyl. engines......that had no zinc at all when new and never had cam problems.
What needs extra zinc is engines with new camshafts and high performance V-8 engines.
If you find an oil, like most 10W-40 grades rated for service LM it has the extra zink. Until a year ago Quaker State Defy had extra zinc but it no longer has.
15W-40 oils are a little "thick" for the splash lubricated engines. Also diesel oils are designed for diesel service.
In the case of the 1939 GMC engine it has full pressure oiling and could handle 15W-40....but....15W-14 n is too heavy for a fresh engine. There I would use 5W20 or 30 with a zinc break-in additive.

My thanks to all for the advice/thoughts. I remember back in the 60's taking the pushrod panel off and the non-detergent oil that was used up to that point left gunk that you could scoop-up with your hands like mud. Today's quality oils are probably a leading factor in our cars and trucks still running so well.

Gene,

I only pretend to know everything. I have always noted that diesel oil (read Rotella, et al) are not good for non-diesel engines. I know that it must be owing to the additives but beyond that I am as lost as my wife with a new road map and GPS.

So please educate me. I may be the only one out here in radio land that does't know but I doubt it.

Just the short answer will suffice. Chipper may have some input, as well, but you know how long winded he can be.

Thanks,
Charlie

I think 15W40 is too heavy but I know people who get by with using it without problems. I use 10W30.

The additive package for a diesel oil is more aimed at the soot a diesle produces. At 2000 miles a diesel engine will make the enngine oil black.
The "worse" of the special oils is most racing oils. They are designed to be run only a few hundred mis so lack any thing in the detergent field.
Yoe just can't beat a good 10W-30 oil for an all around additive package. Also being the best viscosity for all operating conditions of a Chevrolet engine with semi-splash oiling.

gene,

Thanks for the reply. I'm not sure I understand why one couldn't run it in a regular non-diesel engine but so be it.

Two things in your reply give me pause:

a. After 2000 miles all oils look black.
b. You specified a "good" 10w-30. All 10w-30 are good and as long as the letters in the circle are the same they are equal.

I still say that to use any amount of aynthetic is a waste of money. Our old engines don't need it and can't justify the extra cost (of it).

There is an ad on the radio now that says that JD oil will last 10K miles without a change and that they will give a gaaurntee of $6k if you have engine failure owing to the oil. While oil merely gets dirty and doesn't wear out (the additives may), I think the JD ad is pushing it as far as old car engines go.

Thanks,
Charlie

I also use Rotella 15w/40 in all my cars etc . I have driven over 80K miles in my '40 over the last 20yrs .

I don't use this because I think it is ok , I use it because it is ok.

Regards,

According to the 37 Chevy Users Manual it should be non detergent oil because the engine has no oil filter and any wear metal should sink to the bottom of the crankcase. I just bought 6 quarts of ND 30 for the 37 216 engine I am working on at the Museum of Transportation in St Louis.

If detergent oil had been in production in 1937 then that would have been the recommendation. Oil has been improved a lot since 1937. Seeing that it will be in a museum vehicle and probably not driven or run much then the ND 30 will be fine.

They didn't know what detergent oil was in 1937. Also it was not mentioned to use non-detergent as it wasn't discovered at that time. After WWII detergents were added to the oil and that oil was called heavy duty oil. The 1948 owners manual and Service News recommends 'HEAVY DUTY" OIL TO BE NSED IN CHEVROLET ENGINES.....AND THE OIL FILTER HAS NOTHING TO DO WITH IT.
Modern high detergent oils also contains other additives to prevent many engine problems.

Do you know what oil is in it now ? The best thing is to run the same oil all of the time not just weight but brand. I was told many years ago they all have different additives in them they tend to cling together and cause slug. Once the cam and lifters are broke in you really don't need a high level of zinc you would be lucky to have 50 lbs. spring pressure closed.

The Honer

I wouldn't even consider using non detergent oil in any engine, old or new!

I also totally agree!