Pablo that is because after 23 years of working repairing trucks, cars,tractors ,forklifts, all sorts of gas and diesel engines , for a living I can ask why?what is the advantage as I do not sell syn. oil so I can be objective. There are some advantages of syn oil Extreme cold starting and high mile oil drains which most syn users do not take advantage of. I had a 92 v6 cyl. Toyota run on yearly oil changes using Amsoil A friend was a dealer, Redline oil and M1 .At 85,000 miles I did an A/RX cleaning "with the valve covers removes the engine looked brand new" the filter had a black powder coating and my gas mileage returned to almost 21 mpg like when it was new. So much for clean piston rings. I am not an internet expert .I made a living repairing vehicles I know how an engine is lubed.