Engineers Journal / Mechanical

Electric vs internal combustion engine: Top 10 reasons why the former crosses the finish line first

Monday 13 March 2023

To an engineer, it is fairly obvious that an electric motor is a far superior machine to power a car than an internal combustion engine (ICE) – petrol or diesel – write Eamon Stack and Matthew Sealy. However, many assume the opposite after more than 100 years of petrol and diesel cars.

And, other people with a substantial financial vested interest in the motor industry cannot see this reality, or they simply don’t want the status quo to change.

Those who manufacture ICE cars, gearboxes and the suite of ancillary components needed to maintain one, often communicate as if electric cars might be somewhat a compromise, 'a sap to the greens'. This could not be further from the truth. Here are our 10 main reasons why the electric motor does the transport job so much better than the internal combustion engine.

1) Much greater efficiency

How much fuel energy goes into driving the car forward? ICE efficiency varies from 20% to 45%, depending on engine types, to the fuel used and age. An EV is typically 85% efficient. Most new ICE cars have a maximum efficiency of 35% in petrol and 45%(1) in diesel.

This means that most of the energy in the fuel is lost as heat. ICE efficiency deteriorates down to 20% over time. The typical electric motor efficiency, with few moving parts, does not deteriorate significantly over time.

2) Much smaller size

The ICE is a big device and the equivalent electric motor (with the same power output) is at least half the size and weight. You have to place an ICE engine in a special compartment in the car (engine bay) as most if not all of the engine ancillaries need to be close by or attached to the engine block, while an electric motor will fit in line with the front or back wheels.

The new electric Ford F150 uses the engine bay as a massive storage space due to the fact that the ancillaries you normally see on an EV motor are relocated elsewhere to keep the form factor small.

3) No oil – no oil change

The main inefficiency of the ICE results in the generation of heat. To compensate, the ICE needs a substantial cooling system (motor oil), in part to maintain an optimal operating condition to stop the engine overheating and seizing, but also to allow the design to operate in a narrow temperature range to optimise the chemical properties of the engine components.

Heat really plays a big part in how powerful or efficient a combustion engine can operate. The low level of heat from an electric motor requires only a small cooling loop and in modern BEVs with cooling systems, you will find that these are more for the battery pack and not the motor itself.

4) Little noise and vibration

The inefficiency of the ICE also results in secondary effects of vibration and noise, titled NVH (noise, vibration and harshness). NVH consumes lots of time and effort from an OEM perspective to deliver a vehicle that consumers will buy.

To compensate for these secondary effects, the ICE needs sound suppression and shock absorbers to deal with the vibration, which add cost, weight and consumable parts. The noise and vibration of an electric motor is negligible, and as such saves on these initial and ongoing costs of the vehicle.

5) No CO2 or pollution

ICE emits CO2 and other pollutants as it combusts fossil fuel, directly contributing to global warming. The electric motor does not do this directly, but does have some CO2 footprint due to its manufacture and fuel sources. BEVs are not free from producing CO2, but they contribute less in Ireland per km driven with the current fuel mix on the Irish grid and as more renewables come online (to the tune of 80% by 2030) they will only contribute less and less.

With 100% renewables on our grid, then you can say it's CO2 free, or if you have solar and wind at your home, you could already be there now. Most ICE engines also emit toxic chemicals and particulate matter that the HSE say result in 1,000 premature deaths in Ireland each year.

6) No gears

Because an ICE can only generate useful and efficient power at a limited range of revolutions, an ICE needs gears to compensate for its limitation. And to reverse, ICE needs another gear. However, an electric motor can handle the full range of speeds needed without gears in a much more efficient manner and to reverse an electric motor you just reverse the polarity of the electric source.

7) Uniform Power Curve

A Tesla for €100,000 is faster than a Ferarri for €1m. The power curve of an ICE can vary considerably based on its design. There is almost always a trade-off for cost, efficiency, power and torque.

For normal driving day to day, the bit that people notice and like the most is low-down torque, the shove in the back to get you moving forward as you want. The electric motor generates a constant torque from zero RPM, giving the most desired trait of a big ICE, grunt and a pleasant shove forwards, leading to a smooth driving experience.

8) Little maintenance

The ICE needs much more maintenance due to lots of moving parts. Oil filter, oil change, timing belt and other serviceable items like clutches and in some cases engine mounts from all of the engine movement over time. An electric motor requires no such maintenance, and its servicing consists of all the other common parts to all vehicles, tyres, suspension, cabin filters, coolant systems.

9) Long life span

Many years ago the expected life span of an ICE was 160,000km, but with modern advances this is now between 250,000km and 300,000km without major incidence and some basic scheduled servicing.

An equivalent electric motor could last 1,000,000km or more as seen in some high mileage Teslas, mainly due to the simplicity of the motor and lack of ongoing maintenance required to make sure they last this long.

10) Local fuel

The fuel to run an ICE is all imported into Ireland. The fuel for our electric motor is more than 40% homemade (and increasing to our 80% target by 2030) – and you can make your own electricity at home if you have solar PV installed. Ireland is in a great position to be able to hit our goals with wind and solar PV, helping reduce our dependence on foreign fuel sources.

Yes, there is the issue of storage of fuel in a car for both engine types. There is nothing to compare to the energy density of fossil fuels, so the storage tank is relatively small. Battery storage has a much lower energy density and requires a large heavy pack to hold its electric fuel.

Range is an issue as we now have a GOM (Guess-o-metre for range) in our BEVs and some modern ICE vehicles. For many years we didn’t need this range estimate, we used the needle to know how much we had and pulled in to fill up when we needed to. Range is a focus only due to our charging infrastructure and not due to the limitations of an electric motor.

The 10 reasons the electric motor is better than its equivalent ICE engine are exactly the step in the right direction that is needed now. It is about efficiency and the ability to do the same, but to use less.

Electric fuel costs can still be on average, with home charging available, three times cheaper than fuel for an ICE. As sustainable electric generation increases this gap will only get bigger as renewable energy will reduce the cost of electricity across the board, due to cheaper installation and running costs, as well as being less susceptible to external forces causing price fluctuations.

The only real reason the automotive industry is still aggressively promoting ICE cars is profit. And the oil industry is tightly aligned with the automotive industry.

Car makers, for the most part, have not adapted their businesses, so they might serve society with a clearly better car transportation system as the costs to change are substantial. That will be a monumental failure without clear guidance through legislation and by smart consumer choice, to give us what we deserve – a better, cleaner, more cost-effective and sustainable transportation system.

Points of information

As ICE age, their efficiency deteriorates significantly as parts of the overall system degrade and fall outside of specs;
Further from this, ICE is only 25% efficient when you include transmission losses, which are a little higher in ICE versus EV systems due to the larger gearboxes in use for these engines and this efficiency deteriorates slightly with age as wear and tear causes the engine tolerances to loosen;
An ICE needs ancillary components like cooling to operate;
Typically when you look into a BEV’s engine bay, they look comparable in size as the motor normally has the charger and inverter stacked on top of it, but it doesn’t have to be.
Alternative fuels like efuels or H2 used in combustion can be made CO2 neutral, but when burnt they still produce toxic chemicals and particulate matter, so from a health perspective these do not help us as individuals. We no longer need to ignore this awful reality.
Due to the limitations of ICE, you don’t always get this as you want, and sometimes there is a disconnect between what you want the car to do and what it actually does;
When you consider the end-to-end production of petrol with the end-to-end generation of electricity, the ICCT calculates the ICE is 400% more polluting than a BEV.

Authors: Eamon Stack, BAI, M Phil MIEI, is policy officer with the IEVOA. He is executive director of Range Therapy, a non-profit focused on supporting our transition to smart and sustainable energy systems for transport and home energy. Matthew Sealy, B Eng, B Sc (Hons), is the membership officer with IEVOA, and works for Analogue Devices.