Whenever you visit your auto repair or oil change shop for an oil change, you’ll face a choice: regular oil, or synthetic?

Both can be good decisions, based on your vehicle, the type of driving you do, and how often you want to change your oil. But what is the difference between the two?

The answer is the composition, with a little bit or marketing thrown in. Synthetic oil and regular oil both come from the same base of highly refined crude oil. The differences emerge with the additives and through an additional refining process. Synthetic oil also includes some artificially-manufactured compounds as well as a ‘carrier oil’ that controls the size of the molecules and the equal distribution of those compounds. It decreases friction between engine parts, reduces sludge build up, increases overall performance and it lasts longer.

The main disadvantage is that synthetic oil is more costly than conventional oil, so your maintenance visits will tend to cost more. This can be offset, however, by going longer between oil changes. 

Many oil change and auto repair service shops also offer different types of synthetic oils: full synthetic oil and synthetic blends. It’s difficult to quantify the difference between those two types, because there is no defined standard used to identify full synthetic oil. Both are better, for the reasons stated above, than conventional oil. Again, you’ll have to do your own cost-benefit analysis to determine if it’s worth the additional money to go full synthetic, or if a blend will work for you. 

You should change your oil and your oil filter regularly, but the frequency depends on many different factors, including the age of your vehicle, the type of driving you do, how often you drive your vehicle and, of course, the type of oil you use.

Conventional oil changes are suggested every 5,000 miles for more vehicles. If you do a lot of start/stop city driving, you may want to change your oil more frequently. Engines tend to run more efficiently at higher speeds—within reason, of course—and if you start and turn off your engine frequently, it’s possible that the oil will not get up to its ideal temperature and protect your engine as effectively. You’ll also need to change it more frequently if you have an older car, or a turbo-charged engine. 

With synthetic oil, oil changes are recommended every 10,000—or sometimes 15,000—miles. There are performance synthetics that can extend the intervals between required oil changes, too. The general rule, however, is that a synthetic blend will last twice as long as a conventional motor oil.

Deciding between conventional oil and a synthetic blend of fully synthetic oil is a personal choice. Only you know what you can afford, the type of driving you do and the type of vehicle you have. Using synthetic oil, because of its many advantages, is usually cheaper and more efficient in the long run. You’ll have to do the math on your own vehicle to verify that and determine if it’s the right choice for you.