Almost all new engines are designed to run on synthetic oil. To find out if your vehicle actually requires it, just check your owner's manual. If the manufacturer specifies a synthetic blend for your engine, you must use it, or upgrade to a full synthetic for even more benefits. Don't make the mistake of downgrading to a conventional oil to save money. You risk voiding your warranty and causing premature engine wear.

Conventional vs. synthetic oil
If your vehicle manufacturer specifies synthetic oil, never downgrade to conventional.

 

But what if you're driving an older vehicle that was designed for conventional oil? Will synthetic oil help your engine? And, is it worth the extra price? I'll walk you through the service benefits of synthetic oil to help you determine whether it's worth the extra cost.

 

There's simply no disagreement among professionals whether synthetic oil is a better lubricant than conventional motor oil. It is—period. It flows faster on cold engine start-up, getting lube to rotating parts and building oil pressure faster than conventional oil. But you don't have to live in the Arctic to enjoy the "cold flow" benefits of synthetic because an engine is considered "cold" when it's less than 195 degrees F. So it helps even if you live in Key West. On the flip side, synthetic oils are far more resistant to "thermal breakdown" than conventional oil. That means it performs better under high heat conditions and is less likely to produce engine-killing sludge.

 

But is it worth the extra cost for an older engine? If you're the type of driver who changes your oil according to the manufacturer's recommendations, it's hard to justify the added cost of synthetic oil. Conventional oil works just fine in those applications. However, if you often exceed the recommended oil change intervals, then synthetic oil is worth the price. It'll provide a "buffer zone of protection" until you can get around to changing it. And that can mean the difference between an engine that lasts 200,000 miles and one that dies at 120,000.

 

To summarize: If your vehicle manufacturer specifies synthetic oil, never downgrade to conventional. If you own an older vehicle that doesn't require synthetic and you religiously follow the manufacturer's recommended oil change intervals, you won't get enough benefit from synthetic oil to justify the added cost. Or, if you're nursing along an old car that burns (or leaks) lots of oil, don't bother. However, if you're lax about oil changes, or you want to squeeze all the life out of your engine and are willing to spend the extra money, fill it with synthetic.

 

— Rick Muscoplat, Automotive Editor