Consider all the possibilities

Question:

This is in regard to an article in your November 2007 issue on the use of non-detergent oil. I have a 1941 Chevy half-ton pickup truck. I ran the original engine using modern 10W40 oil only to find it smoked.

After two years I replaced the original engine with another 216 cid six-cylinder. I ran this replacement engine for six months and found it also smoked.

I then had the original engine rebuilt and was told by the mechanic to try 15W40 diesel engine oil. I found this to work very well, with no smoke coming from the engine, and I plan to use it in my 1955 Ford tractor.

Answer:

It sounds as though you attribute the engine smoke to the type of oil you were using and I don’t think the connection is necessarily valid. Isn’t it possible that the two engines that smoked did so because they had internal problems and would have continued to do so regardless of what kind of oil you used? In a similar vein, isn’t it possible that the newly rebuilt engine didn’t smoke precisely because it was newly rebuilt and would not smoke even if you used the same modern 10W40 oil that you used previously?

My point here is that it is very important to consider all possibilities when diagnosing any problem in your car, and reaching a conclusion that’s not supported by the facts and circumstances can sometimes prevent you from actually solving the underlying problem.