who knows, im not an engineer. i imagine running it for 3000 miles for a couple months then getting the right stuff is not going to significantly do anything, but thats just my opinion.

I'm with Justin, it is just a bit thicker, so at most there may be a tad less lubricating going on at first when you start the car, in the Winter it may be a little less lubricating also, by the time winter hits I would consider going back to 10W30, then again you do live in Miami, and it does not get that cold there ever, well not what I consider cold anyway.

I am sure somebody that knows more about oil/oil viscosity will post something in regards to using other than factory specified oil.

What I would do is compare readings from a mechanical gage to the vehicles gage at idle and 2000 rpms. It may just be a sensor issue as stated earlier. You will know if the engine is starving for oil, the lifters will start tapping and missfires will come and go. I run Castrol High mileage part synthetic in both my *-10 and blazer. *-10 close to 300K miles and the blazer at 250K miles, both holding great pressure.