If you’re the kind of driver who maintains your vehicle according to the manufacturer’s recommendations, using quality products, and there are no “symptoms” that would justify it, you probably don’t need to think about using additives—those “supplements” for your car’s motor oil or gasoline. There are cases, however, in which a dose of the right additive might be the only way to ensure your vehicle runs as smoothly as it possibly can—but you’ll also want to apply a dose of good judgment, i.e., use the correct amount of additive, at the right frequency.

Motor oil additives

Let’s get one thing straight right away: in our opinion, before you even think about using a motor oil additive, you must carefully consider how well you maintain your vehicle—specifically, how often you change the oil. If you’ve been doing oil changes every three months or 5,000 kilometres, or according to the manufacturer’s instructions, using quality motor oil, you’re already giving your engine all the care it needs to perform up to its full potential, and there is no need to use additives. Moreover, some additives may upset the delicate balance of your motor oil’s composition and adversely affect efficiency.

We should also note that, while we have received practically zero consumer complaints regarding these products, they would appear to be used only marginally.

We certainly recommend that owners ask their vehicle manufacturer whether using a specific additive is suitable—and, especially, what impact the use of an additive may have on the manufacturer’s warranty! Here again, we feel it is important to point out that as of yet we have not heard of any complaints involving warranties invalidated following use of such products—but we do feel that the adage “an ounce of prevention” is worth following, as some manufacturer literature does state that using additives can affect your warranty rights.

Lastly, some of these products aren’t cheap: prices can sometimes be in the $100 range. Before spending that kind of money, have a look at your vehicle owner’s manual—or better yet, ask your dealer, who may be able to recommend a suitable product.

Fuel additives

When it comes to fuel additives, the same advice holds: seek expert advice before pouring anything foreign into your gas tank. There are many different products, each designed for a particular purpose. If your vehicle has been driven properly and is running smoothly, there is no reason to consider using a gasoline additive. In fact, you should only do so if it is recommended by an expert. Here again, the best advice is “read your owner’s manual”—in this case the section on recommended fuel.

The best-known in this category of additive, of course, is good old gas line antifreeze. While this product can work wonders in extreme cold conditions, it is not meant to be abused.

Other popular additives in this category include products designed to clean out your car’s fuel injection system. Over time, deposits can form on valves and injectors and affect their performance (e.g., rough idle, loss of power under acceleration). The golden rule remains the same: consult an expert! There are myriad products out there, and some are much more concentrated than others—enough to damage your vehicle’s fuel system if you use them carelessly. Follow instructions to the letter. For example, an oil change is usually recommended soon after using one of these additives. Lastly, remember that some vehicle manufacturers recommend using a specific product. That’s another valuable piece of information you’ll find in your vehicle owner’s manual.