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When you’re shopping for a new car, there are various aspects & factors to consider. You will start by deciding on the vehicle type; a sedan, a truck, or an SUV. You’ll then move on to picking and choosing the desired features. And let’s not forget, you will also need to consider whether a gas engine car will better suit your needs or a diesel engine would be a better fit. 

You might take a second and wonder, would selecting an engine type make a big difference in selecting your next vehicle? Well as a starter, each engine has its own specifications and mainly each has its own lubricating oil that keeps the vehicle’s parts running smoothly.

In this article, we’ll show you the difference between gas and diesel engine oils.

Gas Engine vs. Diesel Engines:

a closer look at the internal combustion car engine

Before diving into the engine oil differences, let us briefly understand the gasoline engine and diesel engine operations.

In a basic sense, gas and diesel engines have similar operations. Both engines use internal combustion and a series of rapid explosions within the engine to turn fuel into mechanical energy and help the vehicle move forward. 

The difference is how these explosions occur. Let’s take a quick look at the explosion process for each.

In the gasoline engine, the explosion process is:

  1. Intake Stroke – fuel is mixed with air pressing the piston down
  2. Compression Stroke – piston goes up compressing the fuel and air mixture
  3. Power/Combustion Stroke – using the spark plug, the fuel and air mixture get ignited pressing down the piston
  4. Exhaust Stroke – piston goes up pushing the exhaust through the exhaust valve

In a diesel engine, the explosion process is:

  1. Intake Stroke – the intake valve opens, the air gets in pressing the piston down
  2. Compression Stroke – piston goes up compressing the air (heated in excess of 540°C)
  3. Power/Combustion Stroke – at the right time, the fuel is injected & ignited pressing the piston down
  4. Exhaust Stroke – piston goes up pushing the exhaust through the exhaust valve

So the Question Is, Is There a Difference between Gas Engine Oil and Diesel Engine Oil?

Gasoline engine & diesel engine oils are made by combining base oils and additives to achieve the desired performance. 

However, when examining the lubricant’s needed performance for each engine type, we begin to diverge.

1. The Viscosity

When thinking about engine oil, viscosity directly comes to mind, as it is one of the most important lubricant elements. Therefore, getting the right viscosity is of an ultimate importance.

Generally, diesel engine oil has a higher viscosity and lower-temperature pumpability when compared to gas engine oil. If it was used in gas engines, several issues might develop, such as heat generation, premature wear & tear, and more.

2. The Additive Levels

As mentioned earlier, additives are one of the essential elements of the engine oils. However, each engine oil has a different level per volume and different components.  

Diesel engine oil has more additives which makes the oil endure the great pressure of the engine, while if such additives are added to gasoline oil they can affect the car's performance and result in lost compression and efficiency.

3. The Replacement Intervals

With different types of engine oils available in the market, each has a different recommended lifespan, and with the high level of additives in diesel oil, it lasts longer and requires less frequent oil changes.

4. The Catalytic Converter & Emissions

A catalytic converter is a component in the exhaust system that includes porous metal filler and is positioned between the engine and the muffler. Its job is to transform the engine's harmful emissions into stable byproducts before they enter the atmosphere. 

Herein one the major difference between the engine oils.  

Diesel engine oils have a higher anti-wear level, where the catalytic converters in diesel systems are designed to cope with it, while the gasoline systems are not. And therefore, it is not recommended to use the diesel engine oil in your gas engine.

But Why Do Some Motorists Favor Diesel Oil over Gasoline Engine Oils?

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There are many reasons why many car owners might favor one over the other. As engine oil might not be on top of mind with many drivers, it is common for them to select the lubricant solely based on its viscosity. 

Not only that, but some motorists might fall under the assumption that diesel engine oils are more of a “heavy-duty” lubricant, which means it must be better for their gas engines. 

Can I Use Diesel Oil Safely in My Gasoline Engine?

Recently, The American Petroleum Institute (API) released a new category specifications: “C” for diesel oil & “S” for gas engines. 

Finding a diesel engine oil that carries both categories became common. Although they are designed mainly for diesel engine use, those who desire to use one oil in all applications can use it on gasoline engines. 

If the diesel oil carries both categories, we can simply and safely say YES to that question. But remember, if the diesel oil is missing the “S” category specification, it is recommended not to be applied on gas engines.

Ok, So When Should I Use Diesel Oil in My Gasoline Engine?

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If you have a heavily modified with more horsepower gas engine, then swapping to a diesel engine oil will be beneficial. With these modifications, the engine will benefit from a viscosity that will withstand the increased stress.  

Remember before swapping and using a diesel engine oil, check on what successes were found by the engine builders, as they always share insights of what new findings they made.