Featured image for "Best Motor Oil for Hot Weather" blog post. Truck on beach.

Best Motor Oil for Hot Weather

Today’s passenger car or light truck engine has a typical operating temperature of 235 degrees Fahrenheit and can also climb higher when exposed to extreme operating conditions. With turbochargers and direct fuel injection becoming more commonplace, these types of technologies have contributed to increased operating temperatures within engines. Car manufacturers are being forced to make engines with performance improving technologies to meet the tough emission and fuel mileage standards enforced by the US government. In this blog post, we’ll offer some insight on what would be the best motor oil for hot weather.

How Extreme Heat Affects Lubricants

When driving during hot summer months, independent testing has shown that oil sump temperatures can increase substantially throughout the day as the sun beats down on the asphalt. Heat can cause a lubricant to chemically break down much faster, which can lead to deposits and sludge forming inside the engine. The basic rule states that chemical reaction rates double with every 10-degree rise in temperature. With this rise in temperature, deposits can start to form throughout the engine, causing issues. It is for this reason that it is important to be using the best oil for summer conditions in your vehicle.

If deposits within the combustion chamber, this can lead to pre-ignition, thus reducing engine efficiency and worse-case-scenario, damage the engine. Unwanted deposits around piston rings can cause them to stick, thereby reducing compression and power. To combat high temperatures in an engine, we need to take a close look at the two main types of lubricants available to the vehicle owner.

There are synthetic engine oils and conventional engine oils. Let’s see which of the two offers the best motor oil for hot weather.

Conventional lubricants are derived from crude oil. Contaminating elements such as nitrogen, oxygen, sulfur, nickel, and vanadium are typically found in crude oil, and unfortunately cannot be completely refined out of the base oils. During the refining process, the various molecules found in the base oils are separated by their weight. Once the oil refining process is done, molecules of similar weight are left over but are dissimilar in structure. In other words, the molecules are of differing sizes, which reduces their performance capabilities.

Jeep in sand.
There are two types of oil you can use in your vehicle to protect it in hot weather: conventional and synthetic. Synthetics offer superior protection when the temperatures rise in your engine and outside.

The Importance of Viscosity Index

Conventional lubricants have only an average or mediocre level of thermal stability. Conventional base oils have a property called viscosity index (VI.) This viscosity index will indicate the change in oil viscosity in relation to the temperature it is exposed to. The higher the viscosity index, the better the oil is at maintaining its viscosity when exposed to extreme temperatures. This is a key feature to look out for when searching for the best engine oil for high temperatures.

The typical viscosity index of a mineral/petroleum-based conventional oil is around 95. Synthetic oil is chemically engineered inside a laboratory and designed with very specific attributes. These synthetic base oils are considered pure, meaning they contain no contaminants such as those found in conventional oils. Also, the molecular structure is uniform. Every aspect of a synthetic base oil is designed with real purpose and nothing useless is added when it is chemically engineered.

Due to its uniform molecular structure, synthetic base oils offer properties such as superior friction reduction, stronger film strength, enhanced fuel efficiency, and an ability to operate through a vast temperature range. Synthetic base oils far outperform conventional lubricants in all these aspects. In terms of viscosity index, the average VI is greater than 120 and in many instances can go beyond 170. Synthetic oils are extremely thermally stable and hold its viscosity even when exposed to extremely high temperatures. A thermally stable synthetic base oil will not thin out when exposed to high temperatures like a conventional oil will.

White Jeep.
Hot weather and rough terrain put stress on your vehicle. Protect your investment by using the best full synthetic oil available.

How Deposits and Sludge Can Harm Your Engine

A conventional engine oil can break down quickly when exposed to extreme heat. When an oil starts to break down, deposits tend to form on intake valves, which hinders air flow into the motor. Also, as deposits form, it can result in poor sealing of the combustion chamber. If this happens, the engine can start to idle roughly and misfire. Additionally, this can hurt the engine’s efficiency by reducing available power and can also result in more fuel consumption.

This same high temperature that exists during engine operation can start to burn away and deplete the conventional oil’s additive package, thus changing the oil’s original chemistry. As this occurs, the conventional oil starts to lose its ability to lubricate, cool, and protect the engine as it was designed to do. Beyond deposits forming, sludge can start to appear. If this happens, the small oil passages can start to clog up, thus preventing the engine oil from easily flowing to critical engine components, thus leading to undue wear. If an engine uses a variable valve timing (VVT,) then it is imperative that sludge is prevented from forming inside such an engine.

The intricate parts found in this type of system are quite susceptible or sensitive to sludge and can cause them to operate improperly, resulting in a reduction in engine performance and efficiency. During independent testing of a 5W30 pure synthetic motor oil that was manufactured by one of the premier synthetic engine oil manufacturers, it was found that the oil delivered better than 80% fewer deposits than a conventional engine oil. This means that such a synthetic oil offers the ability to withstand extreme heat and is resistant to deposit formation.

This independent test is a perfect illustration of how a 100% pure synthetic-based lubricant would be the best motor oil for hot weather.

Blue Chevy.
When pushing your prized muscle car in hot weather, make sure your vehicle is protected with an oil that can take the heat. Synthetics are up to the task.

Reducing Oil Consumption

When an oil is exposed to high temperature, it can volitalize, meaning that the lighter molecules tend to evaporate, leaving behind heavier components. This is quite common in conventional oils. When this happens, the viscosity can increase, thus making the oil flow much slower and with more resistance, making it more difficult for it to circulate and protect critical engine parts. Also, this can hinder fuel efficiency.


Most likely you’ve experienced oil consumption when you periodically check your oil levels and have found that your engine is using oil, thus requiring you to frequently add oil to make up the loss. When oil volitalizes, it also negatively creates unwanted emissions that are emitted through the exhaust pipe, thus contributing to air pollution. If too much engine oil is consumed and is left unchecked, there may be not enough volume of oil to reach critical engine parts, which can unfourtunately cause motor damage.

Again, during independent tests, a high-performance full synthetic motor oil was tested against a conventional oil and it was found that the synthetic oil consumed better than 35% less oil than the conventional oil. Additionally, since very high quality base oils were used in the formulation of such a high-performance premium product, the additive chemistry also contained much higher quality additives that offered superior resistance to heat, thus offering the potential of enhanced engine performance, longer engine life, and a cleaner engine.

It should be noted that there is a philosophical difference in how a custom high-performance synthetic oil is designed and engineered versus a conventional oil. Conventional oils are typically price-sensitive, meaning they’re designed only to meet minimum standards and to meet a low price in the marketplace. On the flip-side, synthetic lubricant manufacturers take a different view when designing synthetic lubricants.

Their attitude is to make a product that vastly outperforms conventional oils. They are less concerned about price and more concerned about performance and delivering real benefits to the end user. Their thinking is it’s much cheaper to invest more in a high quality lubricant than it is to replace engine parts and components in a vehicle. In terms of protecting your engine during hot summer days, understanding the differences between a conventional oil and a synthetic oil can have a huge impact on how your engine is protected when the temperatures are very hot.

Hands-down, synthetic engine oils without a doubt thrive and earn their keep when the temperature is extremely hot. The best full synthetic oil for hot weather conditions was designed and created for such conditions.

Ford truck.
Off-roading in the hot desert is a fun time. The last thing you need is a failure due to extreme heat. Protect your vehicle with synthetic oils.

Keeping an Engine Clean

Another area to consider when deciding what is the best motor oil for hot weather is to take a look at what type of detergent/dispersant additive package the oil contains.  One of the most common tests used to check an oil’s ability to keep an engine clean is the Sequence IIIH Test. The oil is exposed to 304 degree Fahrenheit heat for 90 minutes, which is a much hotter temperature than your engine will ever experience.

To illustrate how effective a high-performance synthetic oil is versus a conventional oil, a top tier synthetic oil manufacturer put their oil through this test, and at the conclusion, it was found that its viscosity was like that of a brand new oil. When the engine was torn apart, the pistons were nearly spotlessly clean. It was then decided by this synthetic oil manufacturer to run the same oil again in the same engine to see how it would hold up.

SUV camper.
Avoid breakdowns when towing your camper across the hot desert. Synthetic oils were specifically designed to withstand extremely hot temperatures.









The results were impressive. Even though it was run twice as long as the standard test, the synthetic oil still beat the conventional oil test standard by delivering 40% cleaner pistons.

One of the reasons this type of synthetic oil was able to perform way beyond the industry standard was due to the high quality heavy-duty detergent/dispersant additive package. This high-performance detergent/dispersant additive package works at keeping contaminants in suspension and also stops them from settling inside the engine. This allows the contaminants to be filtered out.

Keeping your engine clean during hot summer months is absolutely critical if you’re looking to give your engine maximum protection. Only a heavy-duty high-performance synthetic oil can handle such hot extreme temperatures.

Tacoma truck with bike.
Your pickup truck and motorcycle will love the protection they will get with synthetic oils, especially when the temperatures are hot.








To keep your engine protected during hot weather, then there aren’t many choices available. In fact, in our humble opinion, the best motor oil for hot weather is a high-performance 100% synthetic motor oil. Such an oil will not thin out when exposed to heat, it will not form deposits or sludge, it will keep your engine clean, it will reduce wear, your engine will perform more efficiently, and your engine will deliver greater fuel economy.

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