96 3.5L oil question

I noted while re-reading the Concorde's manual that 5w30 engine oil was
recommended only for easier cold weather starting and that 10w30 was
recommended for average temps above 32F. Given that these
recommendations are 10 years old now and that motor oil has advanced in
quality...would it be safe to say a 5w30 SM/GF-4 would be acceptable
for all-weather use in this engine? Or should I stay with a 10w30 and
if yes, for what reasons?

GrtArtiste

 

I follow the manufacturer's instructions on this engine and use 10W30 most
of the year and 5W30 in winter months. It gets very cold (well below 0 F)
here so the 5W30 is a good thing to do. I do not use 5W30 in the summer in
any of my vehicles since it also gets very hot (above 00 F) in the summer as
well. This may cost me a mile per gallon and require I keep two grades of
oil in the garage, but the engine will last longer as a result.

Bob

 

No, it's not. The viscosity of oil and its "quality" are too different
things. These numbers have to do with viscosity only (how gooey it is).
Stick with the 10W30. The reason is that the 10W viscosity was originally
recommended to suit the clearances in the bearings. These clearances are
bigger now than they were 10 years ago.