Q. I have a motorhome with a Chevrolet gas engine and go to the same place
every time for an oil change. They usually ask me if I want to flush my engine, and they
show me how dark and thick the oil is. I use synthetic oil and change my oil every 5,000
miles. Do I really need to flush my engine once a year as they told me?
No. With regular oil changes, the detergents that are in the oil will keep your engine
clean. The used oil is dark because it is suspending and carrying away dirt and carbon from
combustion. General Motors has issued service bulletins stating that engine flushing should
not be performed.