#### SYNTHETIC OILS

There are excellent synthetics and fuel-efficient oils available that, under the right circumstances, can help provide better fuel mileage and better engine protection. However, these advantages come at a price, which can be significantly more expensive than the cost per quart of conventional motor oils.

Before pouring any synthetic oils into your vehicle's engine, you should consider the condition of the engine and the type of driving you do. Also, check the manufacturer's warranty conditions regarding the use of synthetics.

Generally, it is best to avoid the use of synthetic oil in both brand new and older, high mileage engines. New engines require a proper break-in, and the synthetics are so slippery that they can prevent this. Most manufacturers recommend that you wait at least 5000 miles (8000 km) before switching to a synthetic oil. Conversely, older engines are looser and tend to loose more oil. Synthetics will slip past worn parts more readily than regular oil. If your vehicle already leaks oil (due to bad seals or gaskets), it will probably leak more with a slippery synthetic inside.

Consider your type of driving. If most of your accumulated mileage is on the highway at higher, steadier speeds, a synthetic oil will reduce friction and probably help deliver fuel mileage. Under such ideal highway conditions, the oil change interval can be extended, as long as the oil filter will operate effectively for the extended life of the oil. If the filter can't do its job for this extended period, dirt and sludge will build up in your engine's crankcase, sump, oil pump and lines, no matter what type of oil is used. If using synthetic oil in this manner, you should continue to change the oil filter at the recommended intervals.

Vehicles used under harder, stop-and-go, short hop circumstances should always be serviced more frequently, and for these vehicles, synthetic oil may not be a wise investment. Because of the necessary shorter change interval needed for this type of driving, you cannot take advantage of the long recommended change interval of most synthetic oils.

Most synthetic oils have been tested under the types of extreme conditions that you hope you will never duplicate within your engine. Under conditions of extreme heat, these oils can offer an additional level of protection which you cannot find in most conventional oils. Because of this, synthetic oils are popular for applications such as towing, racing or desert operation. They are also popular with those who are looking for that extra level of protection against engine wear or damage. Consider all of these factors if you are thinking about using synthetic oils.

Fig. 1: The evolution of passenger car engine oil