Originally Posted by mrjlube
Hi guys,im running Motorcraft 5w20 in my grand marquis at 5,000 intervals. I am using the car for my job as a Private driver and car sits idling for 2,3 hrs. at a time 3 or 4 times a week.
Translate that into miles. Both my newer Jeep and Toyota barely turn 1,200 to 1,400 RPM at a steady 40 MPH. So your engine is effectively turning at idle about half of that, (650-700 RPM). Yeah, it's not under a load, but there really isn't much load rolling down a flat, level road at 40 MPH either.
The hour meter is a very good suggestion. I would go with that due to the amount of idling your engine is experiencing. A lot of cop cars and taxi's use them, as do boats. Many cars already have them. My Jeep has a total hour meter associated with the trip odometer. It's amazing how slow your average speed is, when you incorporate the hours the engine runs into the equation.