Modern cars require a lot of different fluids. Most people know about engine oil. However, many people may not realize that engine oil comes in various types, classifications, and consistencies. In addition to coming in various thicknesses and weights — which are designed for numerous uses and applications, from engines to complex gear sets — engine oil also comes in conventional and synthetic varieties. Both types of oils are derived from petroleum and crude oil. However, synthetic oil contains artificial compounds and undergoes various chemical processes to refine it to a greater degree. Synthetic oils have few impurities and usually provide superior lubrication and heat dissipation than conventional oils.

These days, many automakers recommend that owners fill their cars’ engines with synthetic oil instead of conventional oil. Using synthetic motor oil may allow you to go longer in between oil changes, and it can provide better protection for your engine’s internal components over time. However, if your car’s manufacturer recommends using synthetic oil, and you only have access to a conventional version, you may be wondering if it’s safe to switch between the two. As a former professional mechanic and lifelong car nerd, I’ve got you covered.

Yes, you can mix conventional and synthetic oil — doing so will not harm your engine, but it may remove or diminish some of the benefits that come with using purely synthetic oil. The really important thing is that you use an oil with the proper viscosity or thickness as recommended by your automaker. If you don’t know what the correct type of oil for your car is, don’t worry — I’ll cover that, too.

As mentioned, there are various types of motor oil and motor oil brands. If you’re planning to change your oil at home or bring your own oil with you for a professional oil change service, you might feel overwhelmed by the variety of options. Don’t worry — figuring out the type of oil your car needs is pretty simple. The best way to do it is to check your owner’s manual. Depending on your car, you can usually find your owner’s manual in the passenger glove compartment. It will contain a list of maintenance tasks that you need to perform regularly to keep your car healthy. In the section about oil, the manual will provide you with a couple of recommended options.

However, if you don’t have your owner’s manual, you can always pop the hood and check the oil fill cap. An oil type, like 5W-30, should be embossed on the cap’s surface. If none of those options work for you, don’t despair — you can still learn your engine oil type relatively easily. One option is to call your local dealership and ask. Another simple and convenient method is to visit an auto parts store. There, you can ask an employee to look your vehicle up in their computer system. The database will provide you with the type of oil and filter you need to complete your own oil change, and the shop will most likely offer you a few appropriate options at different price levels. If none of those methods work, you’re probably better off visiting a professional shop for your oil change service. The trained technicians will know what oil to use when refilling your engine, and the garage may even provide a guarantee on their work.