I have not owned a car in almost a decade, I have owned nothing but Chevy trucks. And in that I have found and as well as thousands of others that the Vortec motors run the best by using the actual spark plugs as recommended by the factory. So my question is, is this the same with the 3.8 NA motor in my 99 GP. I am looking for fuel mileage, the only reason I bought it was for the MPG and that its big enough to get my family of in it just in case I am without our suburban for some reason. So what spark plug will get me the best MPG (real world, not what an add says), thanks!!