My 2 cents. The company I work for manufactures off highway transmissions. Some of our transmissions are designed to use normal motor oil for lubrication. We test with synthetic and dino. We recommend synthetic in "high load" applications. Synthetic maintains viscocity at higher temps. In our testing, it will hold pressure 20~30 degrees F higer before breakdown.

In our test vehicles, the engines with dino oil were lasting one "life test" of the transmission. We changed the engine oil to synthetic and were able to get two and sometimes three "life test" from one engine! This helped our test budget.

If we run synthetic in our tranmission, it will increase the life over dino. We have not tested synthetic life vs dino life in light duty applications. So don't know how much it improves light duty like a car.

A mobile engineer gave me a description of synthetic vs dino and I will share it. He said synthetic molucules are all the same size and dino is not. Imagine a floor covered with marbles and all are the same size (synthetic) and a floor covered with marbles all different sizes (dino). Which would be harder to walk on? Or two metal surfaces seperated by marbles the same size and different size, which would move smother. That visualazation helped me understand the synthetic benefit.

My 96 850 wagon has over 300K now and has only had dino. The first owner changed at 3000 miles and I change a 5000 miles. At oil change, I am about a quart low. I do run synthetic in my air cooled engines and my boat. Even though my boat has a 350 GM V8, it has a much higher load than in a car so I run synthetic. My Ford truck has 216K and has dino. It uses no oil between changes and has no leaks.

If you use dino and keep it changed, it will do you good. Synthetic will increase the life, but I have not justified the cost vs benefit in light duty applications. Clear as mud?