I need to find out what valve I have been getting from Napa. But I usually go through less than a quart of Royal Purple every 3K to 5K. I rarely check the oil nowadays actually - I should probably pay more attention though. I pour Sea Foam through the PCV port, the oil fill hole, and in the fuel tank a week before an oil change to loosen all the accumulated gunk before I change the oil to get things as clean as possible for the new stuff. I even jack up one side of the VX to get more old oil out. I use Royal Purple followed by a quart of Marvel Mystery Oil in the motor at every oil change. I also use Royal Purple in the trans, t-case, and diffs - and, no, I am not a salesman!
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