CARS.COM — The variety of oils on the shelf at an auto parts store can bewilder those unprepared for a do-it-yourself fill-up, but if you're looking for the fastest answer to whether or not you should use synthetic oil with time as an imperative and money as no object, the answer is a lot clearer than the black stuff: If your car's owner's manual says it does, you do.
For many consumers, however, whether to spend extra money for synthetic oil for an oil change is a difficult question to answer. Manufacturers of synthetic oil promise more miles and better performance when compared with conventional motor oil, but that oil comes at a higher cost — sometimes twice as much per oil change as conventional lubricant. Is the fancier motor oil worth the extra money?
Typically, high-performance vehicles will be more likely to require synthetic oil, as will vehicles that have a turbocharged or supercharged engine. However, if the automaker for your vehicle does not require synthetic oil for your engine, the oil choice is trickier — and there is no clear answer.
Synthetic oil generally resists breaking down for longer than conventional motor oil (typically 7,500 miles to 10,000 miles, sometimes up to 15,000 miles, as opposed to 3,000 miles to 7,500 miles for conventional oil). Breakdown can cause increased viscosity that cuts efficiency to additives being depleted and to sludge building up in the engine. The extra cost of synthetic motor oil is a wash, even if it costs you twice as much, if you have half the number of oil changes. Other touted benefits of synthetic oil for your car include cleaner engines, better flow in cold temperatures, better protection when it's hot outside and better performance with turbocharged engines.
There are also synthetic blends. As the name implies, these are blends of synthetic and conventional oils. These semi-synthetic engine oils straddle a middle ground — they cost more than conventional oils but less than full synthetics, and are said to last longer between oil changes than conventional oils but not quite as long as synthetics. But again, that's a hard number to pin down since manufacturers are vague with their claims for intervals between oil changes. An independent testing lab we spoke with said that synthetics often didn't perform much better than conventional oils do.
Still, older engines may benefit from synthetics because that engine oil is less likely to form sludge.
If your car doesn't require synthetic oil you should perform a cost-benefit analysis, but that can be difficult to do due to vague engine protection and interval claims made by motor oil manufacturers. There may be no reason to spend more on synthetic oil except for peace of mind. Conventional won't be the wrong oil to use in your car.
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