Rexmobile

Hi guys/gals. I was speaking to someone who said driving only highway miles is a sure way to get a "D valve hit". I have no idea what that means - anyone??

Thanks

WHT

It means the person you were speaking with was thinking about steam engines :

The Steam Chest


"There were two basic types of valve gear on steam locos, inside and out. The original valve most commonly used was called a "D" valve, due to its shape.

When they went to superheating, the temperature of the steam was raised several hundred degrees than it had been. This was too much for the lubrication they had available under the conditions of the D valve. Instead they had to go to a piston valve, which didn't have the pressure of steam on the sliding surfaces. A piston is round, the D valve used a square steam chest, so that all engines built with superheating had this double round look. It was possible to add to retrofit a square steam chest with a piston valve, but often this required a new outside steam line."

Well, you did say anyone.

calemasters

Maybe he meant devalue?

Although, with mileage being the same, cars driven on the highway generally have less wear and tear than cars driven in the city.