5w-20 oil and engine lugging

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Apr 11, 2003
Spring HIll
Recently, there was a post (UOA?) of 5w-20 oils and increased wear when the engine was lugged around at low RPM's. IIRC, this was peformed on a Ford truck... Anyone find this thread? Honda calls for 5w-20 in the latest 3.5L V6 models, I have an '04 with 2500 miles on it. I noticed how low the RPMS are when going through some of the hills around here...1000-1100RPM. It produces a decent amount of torque that low, but it strains the engine until it downshifts. The trans will downshift as expected, but I just don't like the fact that 5w-20 oil is in this thing when it's being revved so low. 5w-30 it is!
It makes sense. Lugging is a low rpm condition. Low rpms develop less hydrodynamic wedge lubrication (or whatever the technical term is) which is more difficult for a thin oil to develop. Lugging is also hard on the crankshaft itself. The crank can develop cracks at the journal fillets, eventually splitting in two or three pieces.
There is only one 5w-20 report that shows increased lead wear and that was in TooSlick's 2.4L Toyota Tacoma where 20-weight wasn't the recommended viscosity. He tried two 20-weight oils and found increased lead with both. The automatic in my Acura RSX "lugs" the engine to get good gas mileage and my lead was 0ppm in a 7,000 mi interval with M1 0w-20. All other wear metals were below 1ppm/1000mi. There are many other examples of low rpm engines doing extremely well on 5w-20 (like mscales V-10 truck). Do a search and read the reports.
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