Synthetic Oil

If everyone used full synthetic, Toyota would have left the interval at 7500 miles, which is the official interval specified for my Toyota vehicle. I would not recommend going beyond that. If the car is still under warranty, I always recommend following the manufacturer change intervals. If using a conventional oil, I would recommend changing it every 3000 miles.

Would I pay more for a used car if the owner had used a good full synthetic oil from the first or second oil change and changed the oil at least every

7500 miles? Yes I would, and I think a lot of people would also.

The engine on my 98 V6 Camry runs as good as new. I was just as skeptical as everyone else at first, but after 9 1/2 years I am convinced. I can afford to buy a new car, but I don't have much of a justification considering the condition of my 98 Camry. I have driven hundreds of new rental cars over the years, and none of them have engines that run better than my 98 Camry.

Notice that they don't compare synthetic against conventional oil when determining whether a energy conserving formula is granted. The compare the synthetic against the reference synthetic.

The additives in conventional break down very quickly. Synthetic oil uses much fewer additives because of the nature of its far superior base stock. I will bet that any tests between synthetic and conventional oil conducted at

2500 miles with the same oil would yield even bigger differences.

Notice that when comparing two conventional oils (5W-30 and 5W-20) Ford found .6% difference in fuel economy. So you say there cannot be a 1.0 % difference between synthetic and conventional oil?

The Southwest Research Institute you provided a link for used a 1993

4.6-liter Ford modular V-8 engine. I am sorry but I would not accept any results from an engine design that old, and further I personally would not accept any results from a US manufacturer's engine, whose build tolerances are not the same as Toyotas and Hondas. If you have a Ford engine, go ahead and use recycled conventional oil, because it will not make any difference.

Let me ask you a question. Have you ever changed to synthetic oil in a relatively new car (after about 5K - 10K miles) and observed the difference? I have, and it is instantly noticeable.