Dr.T, you are totally wrong. With synthetic you will have lower consumption- of fuel(1-5% depending on how crappy dino you choose). One of my cars have some 210000 miles on, and it uses maybe 10 oz of oil between oil-changes(13-14000miles). It have seen only synthetic oil since new(Except two Auto-Rx cleanings). With a good synthetic, you will have less build-up of contamination in your engine, as well, compaired to a mineral oil. My other car gets OCI of 18-19000 miles, and it is a turbo-diesel!! This is because my OLM says so. However, there are bigg differences between synthetics. I used castrol syntec on the engine and the OLM said 12-13000 miles. Switched over to RP and the OLM say 18-19000 miles. I asked the Mercedes-workshop where I bought the car, how long this car goes between services, based on the OLM. They told me that it is common to do 10-12000 miles. This OLM also meassures particles and contaminants in the oil. The driving we do is 50/50 city and highway, with a lot of stop and go.