All about motor oils

Learning about motor oil starts with a few basics: viscosity, grades, specifications and formulations to name a few. Start here and master the basics.

Engineering Explained:
Will Thinner Oils Damage Your Engine?

We provided Jason Fenske of Engineering Explained access to our Mobil 1 engineers to discuss how oil interacts with your car’s engine. What do oil weights (AKA viscosity grades) and the numbers on the oil bottle actually mean? Do thinner motor oils improve fuel efficiency? Can thinner oils effectively protect an engine? Watch and find out!

Types of motor oil

  • Engine shown in vehicle

    Synthetic or conventional?

    What's the difference between synthetic and conventional motor oils? Find out about synthetic vs. conventional oils.

  • Mobil 1™ oils help prevent engine wear and oil breakdown

    Types of synthetic oil

    Did you know that not all synthetic oils perform the same? Discover the differences and which is right for your car.

  • high mileage oils.

    High mileage motor oils

    High mileage engines – those with more than 75,000 miles – face a number of potential problems that high mileage oil is specifically formulated to address.


Engine oils are currently classified by a two-letter code. Gasoline engine oil categories start with the letter S (originally designated "Spark Ignition" engine oils, we now associate the S with "Service"). Diesel engine oil categories start with the letter C (originally designated "Compression Ignition" engine oils, we now associate the C with "Commercial").

The second letter is simply a sequential designation of improving quality levels over time. In other words, when a new industry quality level is established, the next letter of the alphabet is used (so SN replaced SM). The letters "I" and "K" were purposefully skipped to eliminate potential confusion with other commonly used designations.

Motor oil basics

  • Back of Mobil 1 motor oil bottle description and product comparison details

    Motor oil labels demystified

    Find out what the numbers, letters, seals and other information on motor oil bottle labels mean.

  • Engine power main

    Ask our experts

    Answers to questions we're asked.

  • How an Oil Filter Works

    How oil filters work

    What do oil filters do? How do you find the right filter? Learn all about oil filters.

  • A qt. of Mobil 1 engine oil sitting on a table in a garage.

    How to improve fuel economy

    Find out how motor oil affects fuel economy, how it works within your engine’s mechanisms and more.


Viscosity is a measure of a fluid's resistance to flow. A fluid with low viscosity flows easily and is often called "thin." Water is an example of a fluid with a relatively low viscosity. A fluid with high viscosity is often described as "thick." Maple syrup is an example of a fluid with a relatively high viscosity.

Your oil warning light can come on for a number of reasons, including low oil level, a failing oil pump, a faulty oil-pressure sensor, blockage in the oil system, excessive foaming of the oil and more. In all cases, you should shut down your engine as quickly as it is safe to do so. Continuing to operate your engine with low oil pressure can result in serious engine damage.

Oil change basics

  • Woman check oil level on her cars dipstick.

    How to change your car's motor oil and filter

    Changing your oil and filter is crucial for long engine life – and doing it yourself is relatively easy and inexpensive. Learn how.

    Learn more
  • 1 qt. of Mobil 1 and Mobil Super Synthetic motor oil with an oil filter.

    Where to get an oil change

    Going to a service center or car dealer is the choice for many vehicle owners. We'll help you find a location.

    Find a service center
  • Car driving on bridge scenic route.

    Used oil and bottle recycling

    Learn how to handle used motor oil and the bottles.

    Start recycling