Motor oil might seem straightforward, but it's more complicated than you may think. Understanding what your engine actually needs can save you money and prevent costly repairs down the road. This guide covers everything from basic oil types to viscosity ratings and brand differences. We'll help you understand those bottle labels and understand what matters most for your specific vehicle and driving habits.

I. Different Types of Motor Oil Explained

Let’s start with one of the most common questions drivers have: What are the different types of motor oil? In general, there are four types of motor oil to be aware of, they are:

• Conventional motor oil

• Synthetic motor oil

• Synthetic blend motor oil

• High-mileage motor oil

Engine Oil Types Comparison

1. Conventional Oil

Conventional oil, sometimes referred to as regular oil, is made from crude oil and utilizes a petroleum-based lubricant. The key function of conventional oil is to help lubricate the sensitive parts of the vehicle’s engine, effectively reducing wear and tear and offering a level of protection against extreme temperatures. Conventional oil is considered budget-friendly compared to synthetic and synthetic blends. However, it doesn’t deliver the same performance, and the service interval (the time between oil changes) is often significantly shorter. 

We recommend conventional oil for customers with newer vehicles still under warranty who maintain regular service intervals. For most daily drivers with newer engines, conventional oil does the job effectively and affordably.

Conventional Oil: Pros & Cons

Pros

• Less expensive than synthetic and synthetic blend oils

• Widely available

Cons

• Increased temperature sensitivity (Thickens in extreme cold and evaporates faster in high temperatures)

• Less durable (Not formulated for longer service intervals)

• Shorter oil change intervals (5,000 to 7,500 miles on average)

2. Synthetic Oil

Synthetic oil is a specially formulated engine lubricant that utilizes chemically modified compounds, working from a base of highly refined crude oil and similar synthetic ingredients. Whereas conventional oil is directly refined from crude oil, synthetic oils are designed at the molecular level to deliver better optimized performance and protection for vehicle engines, especially when it comes to operating under more demanding driving conditions like extreme temperatures. 

Synthetic Oil: Pros & Cons

Pros

• Best engine protection (synthetic vs conventional oil & synthetic blend oil)

• Best performance (Superior viscosity at extreme high and low temperatures)

• Longest oil change intervals (7,500 to 15,000 miles on average)

• Better preserves the life of the engine

Cons

• More expensive than other types of motor oil

• Compatibility issues (older engines can experience issues)

3. Synthetic Blend Oil

Can you mix synthetic and conventional oil? The short answer is yes, that’s what essentially provides you with synthetic blend oil. A synthetic blend is a combination of conventional oil and synthetic oil. As you might already suspect, synthetic blends offer a solid middle ground option between conventional oil and full synthetic. That essentially means you’re paying for some of the added benefits of synthetic (improved performance and engine protection versus conventional) without the associated premium cost of a full synthetic. 

Synthetic Blend Oil: Pros & Cons

Pros

• Better engine protection (synthetic blend vs conventional oil)

• Better performance (Improved viscosity at extreme high and low temperatures)

• Longer oil change intervals (5,000 to 7,500 miles on average)

• Less expensive than full synthetic oil

Cons

• More expensive than conventional oil

• Compatibility issues (older engines can experience issues)

4. High-Mileage Oil

High-mileage oil is typically recommended for engines with 75,000+ miles, though this varies by manufacturer and engine condition. It contains helpful additives to mitigate frequent offenders with older car engines such as leaks, sludge, and increased oil consumption. High-mileage oil can provide enhanced protection, assist in reconditioning seals, and deliver better overall performance from the engine. 

High-Mileage Oil: Pros & Cons

Pros

• Improves performance in older engines (over 75,000 miles)

• Helps prevent leaks from developing

• Dissolves engine sludge 

• Provides rust and corrosion protection

Cons

• More expensive than conventional oil

• Compatibility issues (some engine designs aren’t compatible)

*Related reading (link to): “Synthetic vs. Conventional Oil” and “High Mileage Oil Guide”

II. Oil Grades & Viscosity 

Another crucial attribute we’ll want to consider is the oil grade, which is essentially a measure of the oil’s viscosity. Let’s dig in a bit further.

Oil Viscosity Explained

When it comes to lubricating your vehicle’s engine, the term ‘viscosity’ refers to how easily oil flows at a range of different temperatures. Viscosity is also the difference between oil weights. To help explain it, here’s a simple breakdown:

Higher Viscosity = The oil is thicker and flows more slowly.

Lower Viscosity = The oil is thinner and flows faster. 

Thin oil flows easily but might not protect as well under pressure, while thick oil protects well but might not flow properly when cold. Your engine was designed for a specific viscosity range that balances both needs.

Something to keep in mind: Viscosity is about flow, not quality. As a general rule, thicker oil doesn’t always translate to better performance. When answering, “What’s the best oil for my car?”, factors including the OEM recommendations and driving conditions are key considerations. 

Oil Grades Chart

When looking at an oil classification chart, the higher numbers mean the oil is thicker; lower numbers mean the oil is thinner. This is a useful way to compare and contrast different oil types quickly.

Let’s try using a real-world example to explain oil grades in more detail. Let’s say you have an oil grade of 5W-30 …

• Here, the first number (5) indicates how the oil flows at cold temperatures. Note that the ‘W’ you see alongside the first digit stands for winter. The lower the number, the better the oil flows in extreme cold.

• The second number (30) is an indication of how it flows at normal operating temperatures. Whereas lower numbers highlight improved viscosity in cold conditions, higher numbers highlight greater performance during higher temperatures. So, for example, an oil grade of 5W-30 would be an improvement over an oil grade of 10W-30 at colder temperatures. Conversely, 5W-20 vs 5W-30 oil grade means the latter would be an improvement in hotter temperatures.  

Let’s try one more real-world example to drive things home. What does 10W-30 mean?

• Here, the first number (10) indicates how well the oil flows at cold temperatures. When directly compared to our first example of 5W-30, we can tell that it won’t perform quite as well in cold temperatures because the number is higher (i.e. thicker).

• The second number (30) is an indication of how the oil flows at normal operating temperatures. Because it shares the same number as our first example of 5W-30, we can tell it will perform similarly in normal operating temperatures.

Choosing the right oil grade as outlined by the original equipment manufacturer (OEM) is essential when it comes to getting the best possible performance from your vehicle. Additionally, maintaining any active warranties is dependent on how well you adhere to OEM-established protocols related to oil grades. 

Beyond performance and warranty protection, safety is another key consideration related to oil grades. For instance, using the wrong type of oil can directly contribute to engine failure and subsequent accidents on the road. To avoid a potentially dangerous situation, it’s important to stick to motor oil varieties compatible with your vehicle. 

III. API & ILSAC Classifications

Motor oil involves a lot more chemistry and math than some drivers would like. That’s why dedicated organizations like the API (American Petroleum Institute) and ILSAC (International Lubricant Standardization and Approval Committee) need to set the standards for what circulates through your engine. In short, the API and ILSAC bolster consumer confidence because they help regulate engine performance and protection measurements. 

You can most often find the SN code (used to measure the oil’s performance) posted on the back label of the motor oil bottle within the API Service Symbol “Donut”.

API SP vs SN Oil

API SP is one of the more advanced types of motor oil when compared to API SN. Considered a solid choice for most modern vehicles on the road, API SP is highly effective when it comes to preventing headaches caused by low-speed pre-ignition (LSPI) and timing chain wear. Although API SN still provides important engine protection and performance, modern engines can enhance those effects when outfitted with API SP.   

GF-6 vs GF-5

ILSAC GF-6 is a modern specification for motor oil and provides notable improvements compared to the prior GF-5 standard. The benefits of GF-6 largely amount to improved fuel economy, engine durability, and enhanced protection against low-speed pre-ignition (LSPI) and timing chain wear. GF-6 is broken into a couple of subcategories: GF-6A (provides backwards compatibility with GF-5), and GF-6B (engineered for lower viscosity types of motor oil such as 0W-16). 

IV. How to Choose the Right Oil for Your Car

How do I know which oil is right for my car?

This question comes up a lot due to the many considerations to account for with different oil types. For a closer look on the subject, let’s explore some of the key factors involved in making the best choice of motor oil for your vehicle.  

Key Factors

OEM Recommendations

Choosing the right oil for your vehicle is often as simple as consulting your owner’s manual. The manual is your primary source of information to find important recommendations regarding different oil types, viscosity grades (such as 5W-30), and any other relevant performance requirements worth fitting in. If you don’t have a physical copy of the owner’s manual, you can easily search online using your vehicle’s info (year, make, and model) to narrow down different oil types to your ideal fit. 

Driving Style

Your driving conditions can play a significant role in choosing the right oil for your engine. For example, if you live somewhere with plenty of stop-and-go traffic, you may have different needs than another driver who primarily spends their time commuting on high-speed freeways.  

Weather Conditions

A big reason different types of motor oil exist in the first place has everything to do with the climate. Where you live has a lot to say about the ideal oil viscosity for your engine. Colder climates call for thinner oils with lower viscosity, hotter climates often require thicker oils with higher viscosity to provide the best possible protection for your engine. 

Engine Type and Age

Newer vehicles are equipped with modern engines that can benefit from using specially formulated synthetic oils. On the other hand, older engines may require special types of motor oil that feature additives to help combat natural wear and tear that occurs as the engine ages. 

Driving an electric vehicle? Unlike traditional gasoline-powered engines, EVs don’t require motor oil to operate their electric motors. EVs ultimately have fewer moving parts within the engine and produce significantly less friction compared to the combustion engines that have historically dominated the roadways. Despite this key difference, it’s worth noting here that EVs still do require transmission and gear oils. 

Viscosity

In case you missed this above, viscosity is a term used to describe the motor oil’s resistance to flow. To identify the viscosity, look for the numbers on the bottle of motor oil, such as 5W-30. Here, the ‘W’ signifies the winter rating, and the numbers (5 and 30) refer to the flow attributes at a range of cold and hot temperatures. For clarity, the number next to the ‘W’ indicates the colder threshold, while the rightmost number signifies the heat threshold. 

Oil Additives

Some types of motor oil include special additives including detergents, anti-wear chemicals, and friction modifiers, all of which can offer greater performance from your vehicle’s engine and provide increased protection from the elements. 

Oil Standards

Always look for the API (American Petroleum Institute) or ILSAC (International Lubricant Standardization and Approval Committee) certifications to help ensure your choice of motor oil satisfies the industry standards in terms of both quality and performance. 

Oil Type

Finally, consider the different oil types: conventional, synthetic, synthetic blend, and high-mileage. When compared directly against each other, these types of motor oil offer different things in terms of performance and protection. 

The owner's manual specification should always be your starting point. When customers ask us what oil to use, that's the first place we look. Everything else, like brand preferences, synthetic vs conventional, etc., comes after meeting those baseline requirements.

V. Comparing Major Motor Oil Brands

Pinpointing the best oil brands can be very subjective based on many of the key factors we discussed in the previous section. Let’s take a high-level view of some reputable oil brands, highlighting some of their strengths and special features. 

Valvoline

Valvoline is one of the oldest motor brands in the country. They offer all different oil types, including conventional, synthetic, and synthetic blends. While they have a large presence in the DIY automotive space, Valvoline also has many OEM partnerships. We see consistent performance across their product line, and their MaxLife formula works well for higher-mileage vehicles approaching major service intervals.

Mobil 1

Some mechanics consider Mobil 1 the manufacturer responsible for producing the best synthetic oil for cars because they make it their primary focus. This brand of oil is commonplace among the high-performance, luxury, and turbocharged segments. Mobil 1 is also known for producing high-mileage oil formulas. Their Extended Performance line genuinely supports longer intervals when used in appropriate applications. Popular choice for German and luxury vehicle owners.

Castrol

Based out of the UK, Castrol maintains a global presence with all types of motor oil, spanning from conventional to full synthetic formulations. Castrol oils have a large presence in motorsports and, not surprisingly, are frequently recommended by European auto manufacturers. We see good results with their products, particularly in vehicles where the manufacturer specifically recommends their formulations.

Pennzoil

A Shell company, Pennzoil provides synthetic oils composed of natural gas, setting its manufacturing process apart from other top brands. They offer several options for motor oil, including conventional, high-mileage, and synthetic. 

Quaker State 

Another Shell company, Quaker State caters to the more budget-conscious crowd, producing all different oil types: conventional, synthetic blends, and full synthetic. 

VI. Debunking Common Myths

There can be a lot of interesting takes due to outdated information and anecdotal evidence based on misunderstandings about the properties of different oil types. In this section, we’ll discuss some of the myths below:

Myth #1: “Synthetic oil is always better.”

Synthetic oils provide some great benefits in terms of performance and protection, but exact specs for your engine will determine whether synthetic oils are worth it. A premium price tag doesn’t always mean “better”. Compatibility is key.

Myth #2: “You can’t switch back and forth between different types of motor oil.”

This idea can be easily debunked because many cars switch between conventional and synthetic varieties on a routine basis. For example, moving from a hot climate to a colder climate would necessitate a different viscosity for your engine. Provided you know what you’re doing, you can even mix types and brands. 

Myth #3: “You need to change your oil every 3,000 miles.”

Most modern vehicles (manufactured after 1990) can generally travel between 5,000 and 7,500 miles between service intervals. When using synthetic oil, some vehicles are capable of traveling as much as 15,000 miles between oil changes. 

It’s not hard to debunk many similar myths yourself: Just make sure to read motor oil labels and follow the posted OEM guidelines.

Need help figuring out which type of oil is right for your vehicle? Schedule an appointment for an oil change today at Mavis, and we'll get you back on the road quickly, with the right oil in your vehicle.