How far are you driving on these trips? Unless you get the engine fully warmed up and spend some time at cruise speed, you're not doing much to deal with the problem. I'd suggest spending at least 2-3 hours on a road trip that lets the engine get fully warmed up and enough load put on the piston rings to make sure they're still seated properly. 40K miles on an engine that doesn't get run up to normal operating temp on a routine basis might have worn out the piston rings. Do a cylinder leakdown check to see how well the rings are sealing.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
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