More on which motor oils to use in old cars

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Over the last several issues we have had quite a dialog on lubricants and it has been enlightening— and at times confusing—to say the least. One thing that is not confusing though, is the shop manual for your year and model car. You knew enough about your truck’s transmission to make the change in fluids from one year to another pretty confidently, but most of us don’t. Just because the manual says one thing for one year, doesn’t mean it will work for the next or previous year.

The major complaint most old car owners had when they went away from sperm whale fluid was clunky shifting, and you said your truck’s Hydra-matic shifted a bit abruptly when cold. As for outright transmission failure that would depend on the type of transmission in the car, how it is driven and cared for, and what it was designed to use as fluid.

I have a 1966 Morris Minor convertible in my collection and it takes ordinary motor oil in its standard transmission, not the 90-weight bypoid stuff that most vintage American standard transmissions require. The engineers that designed our cars and the manufacturers who built them went to a lot of trouble to determine which lubricants were best for their products, and for those of us who have not done the research that the manufacturer did, our trying to second-guess and improve things is naive at best, and could be damaging at worst.

As for what to put in your engine, I think there is much ado and hype about motor oils that is just marketing propaganda to get you to buy an advertiser's product. Actually, motor oil is pretty much generic. If the product has the API (American Petroleum Institute) logo on the can along with the SAE symbol, it has met their standards, and it is pretty much the same product across the spectrum as regards anti-foaming, high-temperature service, scuff resistance and breakdown, etc.

There are, of course, oils made for different types of service such as for diesel trucks, heavy-duty applications and for racing purposes, and there are high- and low-viscosity ranges. But, in fact, there is no such thing as an overhaul in a can that will make an old worn engine new again. And there is nothing sold in a jug that will prolong the life of your engine appreciably longer than anything else. If you believe you have found such a magic elixir then keep on using it, but, in fact, which oil or additive you use is much less important than how often you change the oil. So how often should you change your oil? Consult your shop manual.

Vintage cars made 30, 40 or 50 or more years ago do have some special needs if you want to take the best care of them possible, and when it comes to motor oil, you will probably want products that contain 1200-1400 ppm of ZDDP in them to prevent scuffing wear on cams, lifters, etc., especially if you have a high-performance muscle car or have done some radical tuning. But off-the-shelf oil will work fine for a long time if your engine is not set up for high performance.

As for most early American standard transmissions; again use what the manual specifies as much as possible. In cars made 50 or more years ago, GL-1 is probably best because it is likely to be what the transmission was designed to have in it, and it will not damage yellow metal synchromesh rings. However, later standard transmissions will need GL-4 or GL-5 gear oil.

For automatics, there are all kinds of transmissions out there from different eras, so once again, consult your manual. For example, Chrysler products of the 40s and early ’50s that were equipped with Fluid Drive semi-automatic transmissions took 10W motor oil or TDH tractor fluid, ISO 22 grade. But you can use hydraulic jack fluid if you can’t find the right stuff. And as David Symcox points out, mid-’50s GMC trucks equipped with Hydra-matics required motor oil in them.

And as for breaking in engines, I slop the cam with Iskandarian cam lube, and make sure every component is coated with oil and that the oil pump is full, and then I spin the engine without the plugs in it to get some oil pressure before lighting it off. But I just use standard 10-30 wt. motor oil for break-in unless it is an old flat tappet engine, in which case I would use the same grade of oil with more ZDDP in it.