Not always. Running synthetics in places like WI are going to benefit you in gas savings alone. This time of year especially. I start the truck, wait until the coolant comes up to 120 and take off, the oil would still be quite cold even at that coolant temperature and yet my mileage is still pretty good.

It's all in how you look at it I guess. I feel a little more secure knowing that synthetics perform their best at the temperature extremes.

 

I believe the real reason behind it was because the plenum gaskets kept blowing out, which resulted in the death flash.