Originally Posted by Twostick
When was the last time you adjusted the valves on it?

If they've never been done, that might be where at least some of it went.

Any 3406 CAT engines I had were real fussy with valve settings. They called for .015 and .030 and they didn't mean .014 and .029. Fuel mileage would suffer by a few tenths.

Kevin

134,000 and covers have never been off