I posted this picture on Twitter on Saturday evening after a 120 mile drive across the UK. It was taken in the Toyota Prius I own, and I posted it because I was pleased to have used so little petrol on such a long journey. Just in case you haven’t seen the Prius dashboard before, it’s saying 73.9 mpg on a 120.2 mile journey at an average speed of 41 miles an hour.
The first tweets I got back where, 41 mph! That’s so slow, no wonder!
I didn’t have the space or patience to clarify the difference between average speed and highest speed. The route I took was about 80% A roads, the speed limit on an A road is 60. I didn’t break the speed limit but I didn’t slow other cars down. On the short sections of motorways I used I stuck at exactly 70.
The weather was fine, the route was across the eastern half of England, from Gloucestershire to Lincoln, so the last half of the journey was very flat. Hills make a lot of difference and where I live it’s all hills.
Of course the post gleaned the usual reaction from diesel drivers, the ‘I get 238 mpg going up hill pulling a trailer in my 3 ton diesel SUV’ nonsense.
I was told by someone that they got 85 mpg in a Skoda Octavia 1.9 diesel. Impressive, if true, but then I started to think. He posted no pictures and the most cursory of searches reveals 100’s of Octavia drivers saying 60 mpg is very good, and when they have compared actual fuel used in comparison to the readout on the dash, it’s more like 57 mpg.
It’s then I realised that a very easy thing to do on Twitter is say exactly what this individual had said, essentially ‘my dad is bigger than yours.’ It’s barely one step on from 8 year olds in the playground.
I know it’s pointless enraging the diesel heads but I’m also a little immature sometimes. The original post was not meant to goad, I was just impressed that I’d done such efficient driving on such a long journey. But goad it did, the usual rash of ‘but the Prius batteries are much worse than a diesel engine’ and all the normal nonsense I’ve grown immune to.
One thing we can all be sure of, what the readout says on a modern cars dash and what you are actually getting are only loosely connected.
Last year I drove a plug in Toyota Prius. This looks exactly like the regular Prius but has a higher capacity lithium-ion battery that you can re-charge from the mains. This gives the car an all electric range of a mere 12 miles, however if you forget about that, it has a quite remarkable effect on the overall MPG.
How do I know, well, judging from the cars on screen readout it was always doing 99.9 MPG because that’s as high as the standard Prius screen can go. It’s only got 3 digits.
I wanted to know exactly how much it really used. For the first time I actually remembered to fill the tank, reset the mileage to zero, drive the car, charge it when I could, and then re-fill it at the end and do a simple calculation, how much fuel had I put in, how far had I travelled.
The result was impressive. Over 412 miles of driving with 4 re-charges (it only takes an hour to re-charge) my final calculation revealed 124 miles to the gallon. This was in a prototype test version of the Prius, the full production model doesn’t come out until the autumn.
It will be a pleasure to post the MPG readouts which will be so spectacularly greater than the Octavia 1.9 diesel there really is no argument.
Also, while I’m droning on about such nonsense, the figures for the Nissan Leaf, well obviously it doesn’t use petrol but the energy equivalent, as in kilowatts of energy mean it runs at well over 350 MPG.
This is what is so hard to explain, the energy stored in the Leaf’s fully charged 24 kWh battery is equivalent to a mere one and a half liters of petrol, and on that energy the car can travel 100 miles. An electric car is a lot more efficient, but that is a very complex and difficult message to communicate.