I switched to M1 5/40 after running 15/40 Rotella for the past 10 years. I wanted to see if it would quiet the lifter noises. At first, the lifter noise seemed to increase. Not the loud clacking, but you could hear them all ticking at idle. However this cleared up after a good hard run. Now when I start it cold, there is just a little noise, not nearly so loud as before, and just for a few seconds. Then it quiets up to a nice Mercedes diesel purr. I am very pleased with this oil and it has only been less than 100 miles. I hear some people report more improvement after many miles.

My only question is, when summer hits here with 100 plus daily temps and non stop A-C use, will the 5/40 be too thin?

It seems to me that it must flow like 5W to get to the lifters so quick.

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Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
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08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
10 Sprinter 3500 chassis with a Class A Winnebago on it. 56K