Muddled measures in car brochures

One of the last bastions of imperial units is our road network and hence car manufacturers’ marketing campaigns. Ronnie Cohen has been looking at some their promotional material.

The brochure of a particular make of a well-known major Korean car manufacturer, published in August 2016, provides a good example of the muddled measurements in car brochures. It contains information about their hybrid, plug-in hybrid and electric models.

This article starts with extensive use of imperial units followed by metric units and dual units. This combination of measurement units is uniquely British. Miles are used for distances for zero emission driving, maximum driving distance for warranty cover, acceleration from 0 to 60 mph, maximum potential electric vehicle (EV) driving range, top speed, fuel efficiency and maximum driven distance for scheduled servicing.

A glance at more recent brochures shows little change.

Why are miles used so extensively in motor industry marketing and advertising? The answer is obvious. Because that is what is used on UK roads for speed and distance. It shows that the assumption of the UK Department for Transport (DfT) that roads can remain isolated from the rest of the UK economy is nonsense and always has been. Mile-based road signs have a huge influence on the use of units for expressing speeds and long distances in the UK.

Inches are used for wheel sizes, screen sizes, instrument cluster sizes and front and rear brake discs. Another non-metric unit used in this brochure is the PS for engine power output. PS stands for Pferdestärke (horse-strength in German). I suspect many British car buyers would not be familiar with this unit but is still widely used by car makers. PS is also used for both dual speed and single speed clutch transmission.

Metric units are used exclusively for the following:

* g/km for CO2 emissions.
* kW for electric motor power and charge ports.
* kWh for battery capacity.
* litres for engine, fuel tank and luggage capacity.
* volts for power supply.
* cubic centimetres for engine displacement.
* millimetres for engine bore and stroke and car dimensions.
* metres for steering turning circle.
* kilograms for kerb mass/weight, gross vehicle weight, max tow weight and max weight the roof can carry.

Dual units are used for a number of features:

  • Various fuel efficiency measures are expressed in L/km and miles per gallon.
  • Max engine power, max electric motor power and max hybrid system power are expressed in kW and PS.
  • Engine torque and electric motor torque are expressed in newton-metres and pound (lbf)-feet.
  • Potential EV driving range is expressed in miles and kilometres.

The late Chris Howell, who wasted no opportunity to challenge those who supported the UK’s measurement muddle, famously said, “Every country needs one measurement system. No country needs two.” He wasn’t thinking specifically about the automotive industry, but he could have been. It appears that no one involved in the production of the 2016 car brochure, and others like it, asked why the same features need to be expressed in the two different units when one would have been enough.

The brochure shows us the extent of the muddle we are in. There seems to be no rational basis to determine what is expressed only in imperial, only in metric or in both measurement systems. Apparently the authors of the brochure for the new type of vehicle followed established conventions. Why?

Metric Views will be interested to hear from our readers.

5 thoughts on “Muddled measures in car brochures”

  1. Acceleration from 0 to 60 mph? Isn’t that actually based on the worldwide standard of acceleration time from 0 to 100 km/h? And shouldn’t that conversion actually be closer to 62 mph? Another example, perhaps, of ‘close enough will do’.


  2. This evening I saw an TV advertisement for a German car (probably a Volkswagen or an Audi). The pictures showed a left-hand drive car and although the dashboard was not visible, I am pretty sure that it was in km/h. This is not the first time that I have seen left-hand drive cars in British TV advertisements. If the British public are happy to see left-hand drive cars in such adverts (I assume that this is the case, otherwise the car manufacturers would not fund such adverts on Britihs TV), what is the resistance to having km/h on one’s speedo?


  3. @Martin it has been a common trick for many years now to use a left-hand drive car in TV ads… but it is also common for them to have a number plate on them which allows video to be flipped so that it can be shown to look like it’s RHD instead.

    Moving away from that though, what always got me is that owners manuals several of my recent cars (all Vauxhall) had vehicle dimentions exclusively in metric at a time when imperial-only width and height restriction signs were mandatory. I’m not sure what the brochures might have indicated at the time.


  4. This guy has a lot of good YouTube videos on the engineering of autos. This one is spot on because he thoroughly explains the origins of “horsepower” in all its convoluted glory, then finishes up by explaining the pseudo-metric version followed by the piece de re’sistance at the very end, namely, just use the “watt”! 😉
    (just skip the ads if you don’t have a premium prescription):
    Maybe someday the USA will convert. Can’t wait!


  5. Ezra,
    In the design and engineering phase only the watt is used, even in the US. The horsepooper is used only because the marketing people want it because the HP numbers are bigger than the kW numbers to give the deceptions that you are getting more power. To make matters even more deceiving, PS is often used in place of HP but is called HP because the numbers look even bigger yet. Maybe some day someone will come up with new unit based on ponies so the ponypoopers (PP) will be even bigger numbers and get everyone excited. Ignorance is not a blessing, it is a curse.
    The average citizen doesn’t really pay attention to the science. They want to be flattered with big numbers so they can get all goose-pimply thinking they got a real powerful machine until you put it back into proper perspective by using watts.


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