Motor oil for a 1955 automobile



I have a beautiful '55 Studebaker coupe with a solid lifter V-8 engine. The motor has 66,000 original miles and runs beautifully. I have read that the new oils meeting the GF standards have had the zinc removed which is ok for a roller lifter motor but is death on the camshaft of a solid lifter motor. Will use of synthetic oil avoid this problem? I ask because NASCAR runs synthetic oil and their motors run flat tappet cams.


Don’t worry. Now that engine if original was designed for leaded gas. If the valves and seats have not been upgraded, modern gas without a lead substitute added can cause valve problems.


The zinc metallic compounds are greatly reduced in modern oils and especially so with SM oils and can be that way as you said, because new engines have roller lifters. Race car drivers are not especially concerned with longevity but I suppose that is not a factor for your car either as it may not be driven many miles. I’d go with a quart or two of diesel engine oil with each change. Diesel oil has plenty of ZDDP, needed for flat bottom lifters. Yes, it’s OK to mix engine oil; I’ve been doing it for years; sometimes have three different brands in my engine. I don’t believe that synthetic offers what you need, you need ZDDP. ZDDP poisons cat converters so it’s use is being limited and, of course, your car has no cat converter as standard.


Just use the 15w-40 “fleet oil” like Delo which are rated for both gas and diesel engines. These oils are today, and always have been, the best oils on the market.


That’s not much of a concern in a Studebaker because of the extreemly high nickle content of the castings. Cameshaft wear, however, is a concern


Try the newsgroup, these guys have a world of knowledge about restoring/repairing/driving Studes.


I remember the owner’s manual in my dad’s 1963 Studebaker Lark with the 259 cubic inch V-8 engine specifying that non-detergent oils were to be used. However, it also recommended that a can of STP be added at each oil change. I think this engine was the same Studebaker V-8 that is in your 1955 Studebaker.

Now it may be that since Studebaker owned the STP company, this was the reason for that recommendation.

Oils have improved over the past 50 years, and I can’t think of any reason why the non-detergent oil was specified, unless the solid lifter engines didn’t need the cleansing action that hydraulic lifters needed. Perhaps somebody else out there knows why Studebaker made this recommendation.