Engine oil viscosity - noise, ticking, ADB, life, precision...
So my Jeep has finally reached 3k miles and is bugging me to change its oil. Owner's manual and fill cap says 5w-20 for all conditions. Which got me to thinking about a few things, and a few things my Jeep's engine has been doing.
First the recommended viscosity. That's thin for a pushrod engine. I know a lot of newer vehicles are moving to 5w-20. But in most of those, with super-tight tolerances and higher-revving OHCs, that grade makes more sense. But in a low-revving pushrod V-6? We all know Chrysler isn't exactly creating engines with Honda build tolerances. So why so thin? Seems you would want higher shear numbers and film strength in an engine like ours. You'd like to think that the engineers would know best, but could it be that Chrysler was gunning for improved fuel economy numbers and decided 5w-20 was good enough, even if not the best choice? I can't explain why I'm suspicious, but I am.
Which brings me to my own engine. At 3k miles, the valvetrain is noisier than it was when new at cruise and when accelerating. It also has a start-up knock. But here's the weird part - not a cold start knock, a hot start knock. Especially when wheeling. Wheel, shut if off for just a minute or two, and I get a knock for a second that sounds suspiciously like a dry lifter. It's almost like the oil, which has a super-thin viscosity at that point, drains into the pan super-fast and leaves nothing in the parts that should be quenched.
Could be an ADB valve problem with the Mopar filter (which is a Wix, a great filter), and I can see why we have ADB problems with such a thin oil. Could be something else. Could just be that the oil is just plain too thin for our application, draining too quickly and getting past both the ADB valve and out of the parts where it needs to be.
Took it to the dealer for the hot start-up knock, they say unable to reproduce. Now I'm sitting on 6 quarts of 5w-20 for my first oil change, and I'm half tempted to say screw the manual and use 5w-30, it just makes more sense to me for our engines and application.
What do you guys think of all this?