Originally Posted by sgtskid
hmm, thats interesting. What weight oil did you have with it? I have always used a bottle of lucas every other oil change and mixed with havoline 10w30 and a K&N oil filter and I have never had a problem with thickness. It even got rid of my lifter tick that the 4.0 is notorious for (although I think that may be due more to the filter than additive).
Where I work, we have a lab that can do tribology and with 204k on the engine the oil came back great!
I was using 10w40 valvoline max life synthetic blend. I was shocked at how thick the oil was. Oil was jet black too. No real sludge issues, because when I changed the valve cover gasket everything was nice and clean. Is it possible that the thick oil would cause poor idle?