Engine Oils
There are majorly 4 types of oils: Conventional, Semi-synthetic, Fully synthetic and high mileage engine oils

Conventional Engine Oils
Conventional oil is your standard motor oil. It’s manufactured from crude oil that’s pulled from the ground and then refined in a factory. Different additives and processes are done to improve its viscosity (thickness) and engine protective properties, and it’s then bottled and sold for use in your engine. Simple as that.

There are up and downsides to this. The biggest upside: cost. Conventional oil is an extremely budget-friendly option for keeping your engine protected and your car running smoothly. It’s also fairly effective—there aren’t really any bad motor oils on the market these days; as long as you get the right weight and quantity, you can expect reasonable performance. However, their downsides are greater than other types. Because of the naturally-occurring materials, they tend to be less refined. They also offer a lower degree of protection than other types as well.

Full-Synthetic Engine Oils
Synthetic motor oil is manufactured entirely in a factory, or lab. Because of this, they tend to be far more consistent; it’s easier to control manufacturing processes when all of your materials are held to much more stringent standards. Thus, these oils are more refined, and are overall better for your engine

But this comes at a cost—literally. Full-synthetic motor oil is more expensive than conventional oil. Not by a lot, mind you, but generally you can expect to pay anywhere from an extra $20 to $40 for your oil change if you use a full-synthetic oil, depending on how much your car takes. Synthetic oils also tend to last longer, going for longer periods of time and distance than conventional oils do before needing to be changed.

Semi-synthetic engine oils
Synthetic blend oils are a kind of hybrid oil manufactured from both synthetic and natural materials. In other words, it’s a blend of both conventional and synthetic oils to try to capture some of the benefits of both while reducing their drawbacks.

The results are pretty much exactly what you’d expect: they provide better protection and performance than a conventional oil, but not quite as good as a full-synthetic oil. They last a little bit longer than conventional oils, but not as long as full-synthetic. When it comes to cost, they’re a little bit more expensive than a conventional oil, but not as much as a full-synthetic. Overall, they’re an okay middle ground for those looking to keep costs down, but want to give their car a little more help.

High-Mileage Oil
High-mileage oil is a somewhat unique branch of oil that’s entirely on its own. These products have a blend of unique additives included which are designed to help protect engine seals, which in turn helps prevent oil evaporation and improves overall performance. For cars that are getting a little long on the odometer, this extra protection is key as oil burn-off becomes a little bit more common of a problem, contributing to more engine wear and a decreased lifespan.