"For engine oil where the operating conditions are quite normal, why would you choose a synthetic lubricant? Aren't synthetics more expensive?"
Several benefits can be achieved by using a synthetic motor oil, such as better temperature performance, extended drain intervals and improved fuel economy. Although a synthetic may cost more initially, the advantages can pay off in the end.
As mentioned, synthetic lubricants can provide enhanced low and high temperature performance. They feature colder pour points, which enable the oil to start lubricating quicker and the engine to start easier on those chilly mornings or in areas that see temperatures around zero.
On the upper end of the temperature scale, the viscosity of a synthetic will remain more consistent because of its high viscosity index. This means the lubricating film will offer improved protection at higher temperatures.
A synthetic oil also has better resistance to oxidation, thermal breakdown and sludge. While conventional motor oils are recommended to be changed anywhere from 3,000 to 10,000 miles, a synthetic can last much longer. With longer drain intervals, your initial investment in the synthetic lubricant can be recouped. This is where most car owners fall short. They purchase a synthetic oil and then change it at the manufacturer's recommended change interval. However, some synthetic lubricant manufacturers claim their oil can last 25,000 miles.
Synthetics incorporate only the purest oil molecules, which are similar in size and shape. This results in decreased fluid friction, reduced drag on internal engine parts, and an increase in horsepower and torque. With better lubricated internal parts and reduced friction and wear, an increase in engine life can be expected.
In addition, with decreased drag on the internal engine parts, the engine will run more efficiently, requiring less fuel to be consumed. A slight increase in fuel mileage is often seen when switching from a mineral oil to a synthetic oil.
If you plan to own your vehicle for several years or even a couple hundred-thousand miles, then an investment in a synthetic lubricant can pay off with fewer oil changes and engine problems. Keep in mind that synthetic oils work best if they are used early in the life of the engine. Waiting too long before switching to a synthetic can lead to seal leakage. Therefore, be sure to consider all the benefits of synthetic lubricants when choosing a motor oil for your engine.