A little fuel dilution, soot, blow-by is OK

Updated Feb 10, 2021

piston ringI’d like to take some time to discuss a few issues that really aren’t as big a deal as some people might think.

*So many times we get phone calls pertaining to fuel dilution. But if you idle the engine all night and pull the sample the next day, you can bet the dilution will be slightly higher. According to Caterpillar, 3 percent fuel dilution is no problem. 

*Another common concern is high soot levels. However, most engines today are exhaust gas recirculation engines, so soot levels naturally will be higher; the engine is eating its own soot, and some of it has to get past the piston rings along with the blow-by.

*That brings me to another point: Don’t worry about a little blow-by, either. An engine has to have some blow-by, which is what keeps the second ring on the piston seated against the ring gland. If no blow-by gets past the top ring, the second ring will float up and down against the ring gland and wear it out. So don’t be too concerned about some blow-by; just install an oil trap on the end of the blow-by tube to catch the oil as it comes out. Usually it will be about ½ cup per every 10,000 miles driven.

–Bruce Mallinson is the owner of Pittsburgh Power, an engine performance shop in Saxonburg, Pa.