Motor Vs. Engine — What’s The Difference, And Why Does It Matter?

At the risk of starting an internet fight of epic proportions, we’re going to tackle one of the largest debates the automotive world has ever seen: motor vs. engine. While it might seem as easy as simply picking up a dictionary, the chances are, you couldn’t find a good, old-fashioned, 1,000-page brick within 30 seconds in this day and age. That issue has created some issues in and of itself in this debate.

In order to cite our sources, we’ll need to use the online version of the more commonly accepted dictionaries. The problem is, when those definitions don’t match someone’s argument online, the quickest answer is to dismiss their validity because they are online. Rather than face that someone’s preconceived notion might be incorrect, the more reasonable solution to some is that an established dictionary company has thrown its centuries of ethics and morals out the window simply because the medium of publishing has changed.

Motor vs. Engine... which is which?

The Real Definitions

Below, we’ll list the definitions of motor vs. engine from three of the most reputable dictionaries we can access for free. (Note: the formatting oddities are specific to each publication. We left them in the original formatting as published as much as possible, so we aren’t accused of skewing the information.)

Merriam-Webster Dictionary – First published 1828

1: a machine for converting any of various forms of energy into mechanical force and motion
also : a mechanism or object that serves as an energy source

1: one that imparts motion
specifically : PRIME MOVER
2: any of various power units that develop energy or impart motion: such as
a: a small compact engine
especially : a gasoline engine
c: a rotating machine that transforms electrical energy into mechanical energy
especially : AUTOMOBILE

American Heritage Dictionary – First Published 1969

1.a. A machine that converts energy into mechanical force or motion.
b. Such a machine distinguished from an electric, spring-driven, or hydraulic motor by its use of a fuel.

1. Something, such as a machine or an engine, that produces or imparts motion.
2. A device that converts any form of energy into mechanical energy, especially an internal-combustion engine or an arrangement of coils and magnets that converts electric current into mechanical power.
3. A motor vehicle, especially an automobile.

Collins English Dictionary – first published 1979

1. any machine that uses energy to develop mechanical power; esp., a machine for transmitting motion to some other machine

1. anything that produces or imparts motion
2. an engine; esp., an internal-combustion engine for propelling a vehicle
3. motor vehicle
4. Electricity
a machine for converting electric energy into mechanical energy

Motor vs. engine - Coyote

One thing that holds true whether you choose to call this a motor or an engine — it makes a ton of power.

Where’s The Confusion

Those definitions make it pretty clear, that in an automotive application, “motor” and “engine” are interchangeable. So why is there such a confusion? Well, that comes down to engineers (it’s always easiest to blame the engineers). Used as a colloquial way to easily differentiate between an internal combustion powerplant and one that uses electricity, somehow, it has been codified in some circles that an engine uses combustion and a motor uses electricity, and never the twain shall meet.

They will dig in their heels and no amount of evidence will change their minds. (See the debates had over on EngineLabs in regards to the terms “foot-pounds-force” and “pound-feet” of torque for similar examples.) However, we can’t blame all the engineers, as Sarah Jensen from MIT’s School of Engineering dove deep into the root history of the words in an excellent piece HERE. Another great deep-dive into the etymology of the words can be found HERE.

So, we can confidently say that it is completely acceptable to refer to an internal combustion engine as a motor. Using some additional colloquialisms to prove our point, we’ll go put some motor oil in our motorcycle before registering our car at the Department of Motor Vehicles and competing in motorsports. The motor vs. engine debate is settled.

Where does the motor oil go? Won’t it short out the windings?

But Wait…

What about the reverse? Can we call an electric motor an electric engine? That really sounds wrong, doesn’t it? According to the current definitions in the English language of “motor” and “engine, calling an electric propulsion device an engine is completely acceptable as well. You won’t find us doing that any time soon, however.

Is that a motor in an engine bay? Wait a second…

So, where does that leave us? Even though we’ve spent the entirety of this article so far explaining that the words are interchangeable, we will probably continue to refer to internal combustion powerplants as engines, and use the word “motor” when talking about electric powerplants. That colloquial separation of definitions isn’t incorrect either.

At the end of the day, rather than worrying about whether it’s motor vs. engine, calling out people for not using your preferred terminology, and trying to prove them wrong, why not just enjoy each other’s camaraderie? After all, we all have the same interests and should be focusing our disdain where it belongs… on the engineers. (Just kidding, engineers. We love you, too.)

Now here's a real question - would the Tesla be considered a "Rear-engine, rear-wheel drive" configuration?

Now here’s a real question – would the Tesla be considered a “Rear-engine, rear-wheel drive” configuration?

About the author

Greg Acosta

Greg has spent nineteen years and counting in automotive publishing, with most of his work having a very technical focus. Always interested in how things work, he enjoys sharing his passion for automotive technology with the reader.
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