What’s the Best Motor Oil for Hot Weather?

Oil is the blood of your vehicle’s engine. Without it, friction and heat would lead to catastrophic failure. Modern motor oils are engineered to handle a range of temperatures, ensuring proper lubrication regardless of how hot or cold your engine is. But did you know that different types of oil are better suited to different climates?    

The extreme summer temperatures here in Arizona put a lot of stress on your vehicle and its components. Last month we talked about the impacts of heat on your car battery, and this month we are going to go over the type of oil that provides the best lubrication for your engine even when the thermometer is reading triple digits. But first, a bit of a science lesson. 

What Is Oil Viscosity?   

“What is viscosity?” is the real question because viscosity applies to many liquids. The scientific definition of viscosity is a measurement of how resistant a liquid is to flow at a specific rate. In lay terms, viscosity is a measurement of thickness. For instance, honey is a much more viscous liquid than water.    

How Does Temperature Impact Viscosity?   

Most liquids, including motor oils, see a drop in viscosity with an increase in temperature. Think back to the example from above. If you apply heat to honey, it becomes runnier. This is the same process that happens with the oil in your engine.    

What is Oil Weight?   

If you have ever looked closely at a jug of motor oil, you will have seen a set of numbers and letters, like 5W-30 or 0W-40. This number is known as weight and represents the viscosity of the oil at a given temperature range. 

The first number and the letter W represent the oil viscosity in cold temperatures, while the second number stands for the viscosity at warm (operating) temperatures. The lower the numbers, the more viscous the oil is at lower temperatures.    

Almost all motor oils used in cars and trucks are multi-grade motor oils, which are meant to work in a range of temperatures.    

The winter rating is important for people living in areas with cold weather. Cold oil is much more viscous, and if it’s too thick on startup it can cause premature wear and tear on engine components due to lack of lubrication.  

However, in Arizona, this is rarely, if ever, a problem. Issues can, however, occur on the other side of the temperature range. Oils with very low viscosity at high temperatures may not supply enough lubrication to internal engine components.   

What Oil Should I Use in Hot Temperatures?   

Due to the year-round warm temperatures in Arizona, less emphasis needs to be placed on cold start lubrication. An oil with a winter weight rating of 10-15 would be more than sufficient.    

Oil viscosity at operating temperature is more important in hot weather. 40 or 50-weight oils are more durable and provide better lubrication in hot conditions.   

Generally, it’s best to go with what your manufacturer recommends. However, it’s worth understanding which oil weights offer the best lubrication in hot weather.  

The best way to know what oil will best suit your vehicle is to talk to your service advisor or consult your owner’s manual.   

Oil Changes at Borst Automotive  

Borst Automotive is a proud independent auto repair shop with locations in Tucson, Phoenix, and Mesa Arizona. Our expert technicians have the skills to service any vehicle you bring to us. Regardless of the type of oil your car requires, we’ve got you covered. Give us a call or schedule an appointment online today!  


Borst Automotive is here to help when you need it. Give us a call, schedule an appointment, or stop in today!