Some of the data is current, and I am working on collecting the most recent data. It is still valid as a place to start in your own search. The formulation of oils is constantly being updated and subject to change by the manufacturer at any time. Pennzoil GT Perf. The synthetics offer the only truly significant differences, due to their superior high temperature oxidation resistance, high film strength, very low tendancy to form deposits, stable viscosity base, and low temperature flow characteristics.
Synthetics are superior lubricants compared to traditional petroleum oils.
You will have to decide if their high cost is justifed in your application. Normal service is defined as the engine at normal operating temperature, at highway speeds, and in a dust free environment. Stop and go, city driving, trips of less than 10 miles, or exterme heat or cold puts the oil change interval into the severe service category, which is 3000 miles for most vehicles. Synthetics can be run two to three times the mileage of petroleum oils with no problems. They do not react to combustion and combustion by-products to the extent that the dead dinosaur juice does.