Plug-in hybrid cars can do 100mpg, but they need to be honest

Being entirely in favour of, or entirely opposed to, any particular kind of car is a deeply questionable arguing position, I’ve always thought.

You hear people say things like ‘God, I hate electric cars’ all the time; or it could be SUVs, hypercars, microcars or huge off-roaders.

My response is usually along the lines of ‘Go and drive another one’, because the key constant even within individual market classes is difference.

Five years ago the most derided kind of vehicle might have been the plug-in hybrid. No car needs two engines, they said, and no PHEV has a meaningful electric range anyway.

Nobody bothers to charge them up; they’re just a company car tax dodge.

Well, I reckon the PHEV’s time has finally arrived. The Volkswagen Golf eHybrid, road tested only last week, is a mid-sized, mid-market hatchback priced broadly where you would expect it to be, with good performance and refinement and little meaningful compromise to practicality.

It will do 66 miles of real, mixed-road electric motoring on a charge – more around town and at lowish speeds – and it doesn’t need to fall back on its combustion engine to get enough performance to keep up with the traffic.

Then, when the petrol engine’s running, it will return 60-70mpg in free-flowing urban driving, dropping to just under 50mpg at motorway speeds.

You can charge its 20kWh battery at home, from flat, in less than three hours, or in less than 30 minutes on a rapid charger.

And if you’re in a position to do that a fair bit, as I was during the road test, you might well find that, after a week’s testing – some of it quite intensive performance testing, needless to say, with more than 500 miles travelled in all – you’ve actually only used half a tank of petrol and averaged better than 100mpg.

That’s the kind of fuel economy number that the Autocar road test has never seen, as far as I’m aware, and it fairly stopped me in my tracks as I committed it to our test results.

The trouble is, it’s a big fat lie or, if we’re being charitable, a neat piece of sleight of hand.

The car is commendably efficient, I will admit: as efficient, even, as many compact EVs we have tested of late when running on electrons, and it’s more efficient than many compact combustion-engined cars when running, in just the right environment, on hydrocarbons.

The problem is the accounting; and I wonder, frankly, if it’s a problem that car makers must address before people can fully accept the genuine potential that PHEVs have in today’s motoring landscape.

Most have trip computers that take account of both fuel efficiency in miles per gallon and energy efficiency in mpkWh, which you can reset and monitor just like any other trip computer data.

The trouble is that, whether the car is running electrically or in hybrid mode (and therefore principally under petrol power), the trip computer keeps on counting both.

The mpg figure – the one we have been used to watching for so long, and having the odd furtive conversation about in the office kitchen – just keeps shooting up, even if the engine hasn’t run in hours; the mpkWh figure does likewise, even when that engine hasn’t shut down in 100 miles.

Why does this irk me so? Because nothing can be running efficiently that isn’t running at all; and when a car can go for days, weeks – months, even – without bothering its engine to turn for more than the occasional minute, it’s madness to score its efficiency relative to the petrol it clearly isn’t much using.

It would be madness to deduct from a cricketer’s run rate based on time spent drinking tea and eating sandwiches, wouldn’t it?

You don’t give your gas boiler a better energy efficiency rating based on the summer months that it spends doing nothing.

I like to think I can turn out a fair bit of passable copy in a defined period of time, but I’m slower when I’m asleep.

Finally, it seems, there are some really good plug-in hybrids coming onto the scene, with the potential to make really meaningful changes to the way people choose to fuel their cars and deliver other bonuses besides. It’s time to make them honest brokers.