Here's an explanation of the engine oil dilution issue potentially affecting as many as 1 million Honda CR-V and Civic models, transcribed from a video American Honda Motor Co. posted in October. That's when the automaker began notifying owners in cold-weather states about potential problems:
"Your engine uses direct injection to spray fuel into the cylinder. During engine operation, a bit of that sprayed fuel can stick to the cylinder wall, travel down into the crankcase, and mix with the engine oil in the oil pan. Later, that mixed fuel in the pan typically vaporizes, gets directed back to the cylinder and is burned off. But when there's more fuel mixing with the engine oil than vaporizing, the oil can be diluted by the fuel."
Driveability issues can include misfires and a "whirling noise" from the engine compartment, according to a Honda service bulletin. Honda says cold weather can make problems more likely.
Honda extended the powertrain warranty to apply "to any engine components, such as camshafts, rocker arm assemblies, and spark plugs" that are damaged by the oil dilution issue.