Should I switch to detergent oil?

Question:

What is the advisability of converting from non-detergent to detergent motor oil? My old car is an 8-cylinder 1948 Chrysler with 67,000 miles on an untouched motor. I bought this car from the original owner 27 years ago.

I cleaned out the oil pan about 15 years ago and found some soft sludge. Only non-detergent oil has been used in the engine since 1948. The engine runs so well and smooth that rebuilding it just to use modern oil would be something out of the question for me.

I’d like your opinion on converting from non-detergent to detergent oil, given the above information. Am I opening up “Pandora’s Box” on an old engine if I convert?

Answer:

This is a question that has come up repeatedly over the years. My understanding is that detergent oils generally keep very tiny bits of contamination in suspension while the oil circulates so that nearly all of the debris can be caught by the oil filter. Non-detergent oil, by contrast, does not keep the foreign matter in suspension so it tends to sink to the bottom of the pan and other low-lying areas, causing greater accumulation of sludge. My opinion is that you will be OK whether you continue to use non-detergent or switch to detergent oil. Depending on how many miles the car

has travelled since you cleaned the sludge out of the oil pan 15 years ago, it’s probably a good idea to clean the pan again if you are going to switch to detergent oil. If you’ve driven the car a lot over the past 15 years it’s obviously not a bad idea to clean the pan again even if you’re not going to change over to a detergent oil.