Evaluating the quality of a finished synthetic has sometimes been tied to the retail price of the oil. On some Amsoil dealer sites, you'll read about the cost to produce their oil and the expense of the ingredients used. The level of expensive esters in Red Line has been mentioned on this forum in relation to the retail price of that oil. And when it comes to Mobil 1, it has been hinted that perhaps Mobil's desire to compete in the OTC market and keep costs down determines the "quality" of the ingredients used to make Mobil 1. Are these valid ways of looking at the overall quality of what goes into making a company's synthetic oil? I don't think it is. The SIZE of ExxonMobil with its vast production capabilities for various PAOs and esters would tend to be a big plus in enabling them to use the very best ingredients while keeping the retail price at the lowest level possible. Therefore, I'd be willing to bet that ExxonMobil could produce a synthetic oil with a base oil comprised of 40% esters and 60% PAO much more cheaply than Red Line could produce the same oil. This would of course translate into a lower retail price than Red Line would have to charge. Of course, the best way to evaluate any oil is to use it and test it. But trying to evaluate the quality of a synthetic based on price is like comparing apples to oranges when it comes to saying that Brand X is better than Mobil 1 because it costs more. The economics of proudcing sythetics just don't work that way.