[Dave at Pelican Parts]

The bottom of the tuna can has a nut that holds the whole thing onto the engine. It is super critical that this never be over-tightened, as it will break a boss inside of the case. New engine time. The torque spec is all of nine lb-ft. If you don't have a wrench capable of measuring that, get one. (Possibly an inch-pound one; 9X12 = 108 in-lb.)

You don't have to remove the tuna can for an oil change, but you will leave about a half-quart of oil in the can if you don't.

The oil capacity of the engine with the tuna can is pretty close to 4 quarts. The cooler will add to that, but I am not sure how much. Depends on the size and construction of the cooler, and the hoses that go to and from it.

The oil in the cooler will drain into the sump if the inlet and outlet and all of the hoses are below the level of oil in the engine. Hoses that go up above that level will keep oil trapped in the cooler. I would check the oil normally, with a warm engine not running.

--DD