Types of Motor Oil: How to Pick the Correct One

Motor oil is used for lubricating internal combustion engines. Engines have a lot of moving parts and with that comes heat from friction. The main function of motor oil is to reduce friction and lubricate the individual engine components.

Motor oils are designed for specific use cases. In fact motor oil is more than just motor oil. It is a blend of several different substances and additives that work together to protect the engine. These include base oils, detergents, dispersants, friction modifiers, foam inhibitors, corrosion inhibitors, and more. Motor oil is typically made of primarily base oil and 5-30% additives.

Your owner's manual is a good starting point when it comes to picking a motor oil suitable for your vehicle. The manual will offer specific information about the weight and viscosity requirements based on your engine.

Types of Motor Oil

Most drivers will opt for the recommended oil and filter every 3,000 miles or 3 months. Frequent oil changes means you likely won't need other types than conventional. With that said, brands like BMW only recommend using synthetic oil with their engines.

Motor oil is segmented into four main categories:

  • Conventional
  • High-mileage
  • Synthetic blend
  • Full synthetic

Conventional Motor Oil

A majority of engines use conventional motor oil. They are formulated in a range of viscosity grades and are ideal for basic/light-duty engine designs. Most car engines don't require special performance-enhancing features (additives), and conventional motor oils are best suited for these cases.

Full Synthetic Motor Oil

Synthetic motor oil is an engineered product, with enhanced additives and almost no impurities. These types of oil go through a chemical production process where the oil molecules become more uniform than conventional oil molecules. This process results in several added benefits.

The benefits of synthetic oils as compared to conventional are:

  • They perform well under extreme temperature conditions (highs and lows). They have a high viscosity index that ensures their oil molecules don't clump together at extreme temperatures.
  • They offer better protection against engine deposits that lead to the formation of oil sludge.
  • They can reduce friction between the engine components. This results in improved fuel efficiency and improved horsepower through engine drag reduction.

With all these benefits, why shouldn't everyone use them? These oils are expensive and should only be used when required.

Still, if you subject your vehicle to very hot summers and very cold winters, not to mention use it for towing and hauling, then synthetic might be the right option for you.

Synthetic Blend Motor Oil

Synthetic blend motor oils are a mix of conventional and synthetic as well as some additives.

Here are some of their important features:

  • They function well under particularly low temperatures.
  • They provide increased resistance to oxidation in the engine.
  • Their volatility is quite low, which means they don’t evaporate very fast, leading to less oil loss and improved fuel economy.
  • They are popular among pickup and SUV owners for their high load protection.

Their main advantage is that they are cheaper than synthetic oils. Despite this, their features are quite similar.

High-Mileage Motor Oil

This particular category is for very high mileage (75,000 miles and above). These days vehicles last a lot longer than they used to. Refiners saw this problem and created a solution.

They offer quite a few benefits for older vehicles:

  • They prevent oil leakages and reduce burn-off of oils when traveling long distances.
  • Their viscosity is generally higher due to viscosity index additives. This means they can seal cracks in the engine.
  • They have anti-wear additives that help in slowing down the wear-and-tear process.
  • They can also help reduce emissions and smoke in older engines.

A very important substance in these oils is the seal conditioner, which improves the flexibility of internal engine seals. As a vehicle gets older, crankshaft seals harden and lose their flexibility. So, when temperatures are low, these seals may start to leak.

Seal conditioners in high-mileage motor oils increase the flexibility of these seals. They flow into their pores and fill in the cracks.

Once your vehicle goes over a certain mileage, you might want to switch over to high-mileage motor oil.

Final Thoughts

There are four main types of motor oil available. Given that most people aren't experts, choosing one might prove to be quite tricky.

To sum up:

  • Conventional oils are a good choice for most engines.
  • Synthetic oils protect specialized engines.
  • Synthetic blend oils offer the best features of synthetic and conventional oils at a lower price than full synthetic
  • High-mileage oils are the best choice for engines that exceed 75,000 miles.

It's best to make an informed decision based on your engine specifications and vehicle usage parameters. To reiterate, check your owner's manual, and you can't go wrong.

Richard Reed
I've been a General Manager of a moving company and I've also been a Professional Mover for over 30 years. I've driven flat beds, reefers, dropdecks, moving vans, heavy machinery, etc. In my time as a Mover I've driven over 1,000,000 safe miles. My days of moving and driving truck are past me but The Vehicle Lab allows me to share the knowledge I've gained over the past 40 years.
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