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Discussion Starter #1
I have always used 10W-30 Mobil One synthetic on my 94' Deville Concours. I recently tried using 15W-50 Mobil One for the summer season. I did this on my 97' Seville with no problems. In fact it was noticably smoother at highway speeds during the summer months. On the Deville, I keep getting the "check oil level" message when it is not low. In the most recent situation it was only down half a quart. Am I hurting anything by running 15W-50? I assumed that the 97' and 94' Northstar engines would respond the same to the different oil weight. Has anyone else experimented with this?
 

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White Diamond '03 DHS (with DTS floor shift)
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The message is not from the oil. It is a dirty connection or a failing sensor. Personally I'd stick with what the factory recommends.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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:thepan: 15W-50 is good for commercial diesel or 454/455 c.i. boat engine service. (Is the jug labeled CC/CD?) It is not good for automotive engine service, especially in Michigan, and will probably cost you a mile or so per gallon as well as starve the engine for lubrication at cold startup. Trust Ranger: Go with the factory recommendation.
 

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Discussion Starter #4
Turned out to be a bad connection. Light corrosion on the female end of the oil sensor plug. It has been cleaned and everything seams to be fine.
As far as the oil, I liked the 15W-50 in the Seville in the summer, especailly on the highway. I do a lot of driving "up north" and to the west side of the state (2-3 hours one way) and lately the weather has been unusually warm. The oil I'm using is 15W-50 Mobil One "Performance Formula." The spec says API CF/ API CD. Maybe it's overkill, if I don't like it I'll change it back. Eitherway, I'll be changing it back in mid September anyways before it cools off.
 

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Sedan de Ville, CTS
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I would also worry about the 50 W going back down into the oil guides quickly enough. Engines 40 years ago had tons of room then and there. Today, engines are more highly refined.
 
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