Re: Synthetic Oil
Synthetic oil does not thicken when it gets cold as severely as conventional oil. Therefore, your engine bearings, lifters, timing chains, and cylinder walls get lubricated much quicker after cold startup with synthetic oil. This fact alone justifies the extra cost of synthetic oil--even if you choose to change it as often as conventional oil.
Because of the better viscosity index (does not thicken as much when cold), your chances of the engine starting in below zero weather are improved, also.
If you don't believe the above, take a small transparent container of conventional oil and a second small container of synthetic oil of the same rated viscosity and put it in your freezer overnight. Then, see for yourself how much better the synthetic oil flows when cold.
As someone said above, there are no cons with synthetic oil--unless you consider the extra cost to be a con. As many of you already know, jet airplane engines would not run with conventional oil.
2009 CXL FWD with Tow Pkg. Red Jewel Tintcoat '09 purchased 10/08. Traded '04 GTO and '07 Grand Prix GXP. Getting Old?