Common Mistakes When Analyzing Your Car's Motor Oil

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Confused about what motor oil to put in your car? Here’s the most important step to take first as well as two common mistakes car owners make with their motor oil analysis.

Choosing your car’s motor oil is not always a simple decision. When choosing motor oil, it's essential to consider the manufacturer’s recommendations, how your vehicle is driven, and your vehicle’s specific needs.

Arguably, the most important reason for choosing your motor oil is the fact that you know that choosing the right motor oil is crucial for ensuring engine performance and longevity.

With that in mind, some car enthusiasts take their car's motor oil a step further by staying abreast of the latest motor oil formulations due to what you used last year may have changed this year.

BASIC CONSIDERATIONS ABOUT YOUR MOTOR OIL

To ensure that your car’s engine lasts as long as possible, some of the most basic considerations to keep in mind about the motor oil you use in your car include:

Motor Oil Viscosity: The importance of your motor oil’s viscosity is that it is the foundation of several factors when it comes to your car’s engine such as lubrication, cooling, fuel efficiency, and protection from unwanted sludge development. Motor oils come with viscosity ratings like 5W-30 or 10W-40. The first number (e.g., 5W) represents the oil’s viscosity at cold temperatures, while the second number (e.g., 30) indicates its viscosity at normal operating temperatures. Refer to your vehicle's owner's manual for the recommended viscosity range.

Motor Oil Type: Motor oil types very considerably in both their formulation and their price. Types of automotive oils to consider range from

  • Conventional Oil: Suitable for older, less demanding engines. It is generally less expensive but requires more frequent changes.
  • Synthetic Oil: Provides better performance and protection, especially in extreme temperatures. It is more expensive but lasts longer and can improve fuel efficiency.
  • Synthetic Blend Oil: A mixture of conventional and synthetic oils, offering a balance between cost and performance.
  • High-Mileage Oil: Formulated for vehicles with over 75,000 miles, containing additives to help reduce oil consumption, leaks, and smoke.

Motor Oil Additives: Additives play an especial role in your car’s engine. Most motor oil types contain the three following additives, albeit at differing concentrations depending on their function for a particular motor oil formulation and intended use:

  • Detergents and Dispersants: Help keep the engine clean by preventing sludge buildup.
  • Anti-Wear Agents: Protect engine parts from wear and tear, particularly in high-stress conditions.
  • Corrosion Inhibitors: Prevent rust and corrosion within the engine.

Engine Age and Mileage: A vehicle’s age and its condition are factors to consider. A general rule of thumb is that newer engines may benefit from synthetic oils that provide superior protection and performance; whereas older engines may benefit from high-mileage oils that can help address issues like oil leaks and reduced compression.

Oil Change Intervals: In general, oil change intervals when using conventional motor oils typically require more frequent changes than your car’s manufacturer may recommend. The current consensus outside of manufacturer recommendations of every 10,000 miles is notably more often at every 3,000 to 5,000 miles.

If you use synthetic motor oils, the oil change intervals in some cases recommended by an auto manufacturer may be as high as every 20,000 miles. The consensus online by automotive experts who work on cars for a living is that 7,500 to 10,000 miles is a better mileage limit. However, others state that it really depends on how a vehicle is driven. For example, driving off-road in dusty conditions or desert environments or when frequently towing a trailer or RV.

3 IMPORTANT CONSIDERATIONS WHEN CHOOSING A MOTOR OIL

According to a recent The Oil Geek YouTube channel episode where the host reveals why he prefers Pennzoil to Mobil1, he pointed out the most crucial step to take first when choosing a motor oil as well as two common mistakes car owners make with their motor oil analysis.

Here’s the video posted below where the host makes note of formulation changes in two popular motor oil brands and what oil analysis of each reveals. However, the meat of this article’s focus is derived from some of the comments and recommendations he makes during his discussion of what he found comparing Pennzoil to Mobil1.

For your convenience, a summary of useful information from the video relevant to this article’s focus is provided below the video.

 

Summary of Take-Away Message Focus of Video

The Most Important First Step: Always begin with your vehicle’s manufacturer specifications for the motor oil to use in your vehicle.

Consulting your vehicle’s owner's manual and possibly speaking with a trusted mechanic can provide guidance tailored to your situation.

If you are considering taking your car's motor oil decisions to the next level, the host recommends first starting with the two following basic points as a foundation to build from:

  • OEM Recommendations: Always follow the oil type and viscosity specified by the vehicle manufacturer. These recommendations are based on the engine design and performance requirements.
  • Certification Standards: Look for oils that meet industry standards such as API (American Petroleum Institute), ILSAC (International Lubricant Standardization and Approval Committee), or ACEA.

Two Common Mistakes Car Owners Make with Their Motor Oil Analysis: Once you've addressed the above recommendations and want to begin trying out other motor oils, there are two common mistakes beginning oil experimenters make: (1) Not realizing the limitations of commercial motor oil analysis; and (2), not flushing the oil correctly when switching from one oil type to another.

  • Invest in a Magnetic Oil Pan Drainplug: As it turns out, relying solely on the occasional motor oil analysis of a sample of your drained oil has its limitations. Namely, it only detects wear and tear indicators at the micron level and not when metal particles are larger sized. In other words, oil analysis reveals that which you cannot physically see, is only part of the picture that does not include what you can see in the motor oil that is could be indicative of a problem that is developing in your engine. To get a bigger picture of your engine’s health and assist you when comparing motor oil brands of the same recommended viscosity, the host recommends investing in a magnetic oil pan drain plug to help catch some of those metal wear and tear particles the typical oil analysis might miss or underreport.
  • Under-flushing Your Engine Between Oil Type Changes: If you decide to experiment between different motor oil brands (within the manufacturer recommended viscosity) and send samples out for analysis during oil changes, you must go through at least two oil changes first to ensure you are not carrying over contamination from the previous motor oil used. This makes sense in that when you drain your motor oil you will not get the entire amount of motor oil added originally, It will take at least two flushes (changes) of motor oil to ensure that the next analysis will be that of primarily the new motor oil used and tested.

For additional motor oil related articles, here are three useful ones for your consideration:

Timothy Boyer is an automotive reporter based in Cincinnati. Experienced with early car restorations, he regularly restores older vehicles with engine modifications for improved performance. Follow Tim on Twitter at @TimBoyerWrites  and Facebook for daily news and topics related to new and used cars and trucks.

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