I've been using 20w50 for ever and was just convinced that it may be a bad idea and I should switch to 5w30 as suggested by the manufacturer. Well, I did. Immediately, my engine began to lope when it idles. Still ok when driving but it lopes at idle. This happened with the very 1st start after changing my oil. Could this be a coinsidence or should I switch back to 20w50? Does anyone know of 20w50 being a problem or of 5w30 somehow causing this idle problem?

 

Not sure if its the problem, but 5w30 is kind of light for Reno. What is the coldest temperature you've seen there recently (past couple years)?

10w30 is what I run year round now up here, and we are by no means the coldest in the nation, but we regularly see -10 or -20 or so during the winter. A block heater helps.

If it gets hot enough there, I don't know of any reason why you couldn't run that heavy of oil (20w50) and not get away with it.

 

I know up here in Michigan I always run 5W30 in my vehicles. Every one i've had and haven't seen any problems.

 

That's a pretty severe change in oils, perhaps the engine just sounds different and you aren't used to it.

I'd go 10W40 or that 15W40 Rotella T in Reno. I've never tried it, but I've heard really good things about that Rotella T, especially on a higher mileage engine.

 

not sure ?