The main benefit of using synthetic oil is that it prolongs the length of time before an oil change becomes necessary. With conventional oil, a drain is recommended every 3000 miles, whereas when synthetic oil is used a change is not likely to be necessary for 5000 – 7500+ miles. This makes using synthetic oil vastly more cost-effective for the average driver, despite the fact that the initial outlay for the product itself is higher.

The primary function of oil is to provide lubrication between moving metal parts reducing friction, wear and heat and thereby ensuring a long lifespan for an engine. All of the high quality oils claim to be superior at performing this function, but there are differences between the top brands in terms of what they deliver. Tests on viscosity, wear and horsepower combined with more long-term consumer testing have shown some variations in overall performance.

Pennzoil Platinum Full Synthetic Motor Oil

With high performance, and used oil analysis showing consistently good results even with long oil change intervals, this very reasonably priced option is hard to beat. It costs significantly less than many competitors and is available in a wide range of retail outlets. It has low engine deposits and
increases horsepower and torque by reducing friction.

Amsoil 100% Synthetic Motor Oil

This performs incredibly well even over long periods between changes, in particular the Signature Series available in 0W30 which is known for its longevity.
It is much more of an investment that Pennzoil (usually around double the price) but if the money is available, it is worth it.

Castrol Edge with Syntec Technology Full Synthetic Motor Oil

This is generally the most often recommended by manufacturers and mechanics. It is a good choice for high-mileage drivers as it has long drain intervals and superior protection against wear. This is a selective blend of low friction base oils and proprietary additives aimed at power, fuel efficiency, and engine

Mobil 1 Synthetic Oil

This is probably the most well-known synthetic oil, as it is the choice of many top car manufacturers, such as Porsche and Mercedes-Benz AMG, as the factory fill. This is because of its superior performance and its ability to extend the life of an engine, all of which is reflected in its relatively high price.

BP Visco 5000

This is suitable for a wide variety of engine types and makes of car, gives excellent engine cleanliness, high performance and long drain intervals. It has reduced production of sludge and wear when compared to the industry standard.

Other synthetic oils which have tested well and been reviewed favourably include:
Shell Helix Ultra
Royal Purple
Valvoline Synpower
Quaker State Peak Performance
Torco MPZ SR-1