Changing the oil in your car is like brushing your teeth. It’s important, and you are reminded to do it a lot. An improperly oiled engine is much more prone to serious mechanical injury, so there’s no excuse to not keep fresh oil in your engine. If you are already on CJs, then it’s not necessary to belabor this point. Most Mustang owners will fret over a scratch, so they’d certainly keep their engines running as smoothly as possible. That being said, there are different types of oil you can use in your car. If you go to a shop to have your oil changed, then you surely have heard a spiel or two about synthetic oil. Though this can feel like a typical upsell attempt, it’s not an entirely disingenuous effort. While synthetic oil is not always necessary for your Mustang, it is a justifiable added expense.
Common Myths About Oil
First off, there are some myths and confusions around the different types of motor oils that do affect consumers. There isn't too big of a difference between the base materials used in synthetic and regular motor oil. Both are made of refined petroleum, meaning that synthetic isn’t "synthetic" in the traditional sense of the word. The main reason that it's called synthetic is that it is further chemically refined beyond what conventional motor oil is. This is important to point out since there is a belief that synthetic oil is a greener alternative to conventional motor oil because it isn’t made out of oil at all. It is made out of oil, but that doesn't mean that it isn’t a greener option necessarily.
The cheaper option is conventional motor oil. It lasts around 3,000 miles before it should be changed. The 3,000-mile replacement range is a bit dated, however, and conventional oil can last longer in modern engines.
Like synthetic oil, traditional motor oil is full of various additives in order to help it perform better. Among those additives are ingredients that are intended to protect the engine, collect engine residue, and maintain the proper viscosity, or thickness, at the correct temperatures. Two numbers are listed on the bottles of conventional motor oil, with one followed by the letter “w” for winter. Basically, the first number represents the viscosity of the oil when it is cold, and the second is the viscosity for when it is at the standard operating temperature of an engine. For an example, let’s look at the recommended oil viscosity for a recent Mustang. For standard driving conditions, 5w-20 is the recommended grade of motor oil to be used in a current 2018 Mustang. That means that when the oil is cold, it doesn’t get too thick (5), and when it’s hot, it doesn’t run too thin (20). Either of these conditions could be potentially dangerous to your Mustang’s engine. The way in which conventional oil is able to have this dynamic viscosity is through certain additives that make the oil more viscous when it is warm and less when hot, keeping it more effective all throughout the temperature band.
The reason conventional oil needs to be replaced depends on its additives, however. As the engine is used, some of these chemicals heat up and evaporate, eventually leaving the oil inoperable.
Synthetic oil lasts much longer than conventional oil, usually needing to be replaced around 10,000 to 15,000 miles of use. Part of what makes the oil synthetic is its complicated refinement procedure. Unlike conventional oil, synthetic oil is engineered to have all of its molecules be as uniform as possible. This aspect of synthetic oil composition means that it can better resist friction, reduce sludge buildup, and ultimately increase performance. The chemical properties of synthetic oil essentially mean that it is less reliant on the additives to function. Even when the additional chemicals are burned out of the mixture, the oil can continue to function fine. Although synthetic oil isn’t “green” in the way that many people think that it is, it does last longer, which does mean that less oil is required.
Synthetic oil was initially made for high-performance engines, specifically for aviation, so it is an all-around heartier oil option. That’s also part of the reason that synthetic oil can cost up to twice the price of conventional motor oil. However, its longevity can mitigate the higher upfront cost. By being so sturdy an oil, it doesn't need to be replaced nearly as often.
Is Synthetic Oil Worth It?
Synthetic oil isn’t always the optimal choice, even though it is a good one. Say you only take your Mustang out on short trips every now and then. If you don’t really rev your Mustang all that much, then the oil won’t heat up enough to burn up too many of the helpful additives. In that case, opting for synthetic oil might be an unnecessary expenditure. That being said, there aren’t any engines that absolutely need regular motor oil. If you use your Mustang frequently, opting for synthetic oil over regular can, at the worst, cost you a few extra bucks, but at the best, ensure a longer-living healthy engine.