Trending oil and diesel prices

November 3, 2008

Since April 07 I’ve been keeping my diesel reciepts (for work). Though diesel and petrol (gas) prices haven’t followed each other perfectly, its still an interesting graph. I’d like to see what it would look like if I also fed in the €/$ exchange rate… there is always more you could to do with excel… 

Graph of Oil and Retail Diesel Prices (Gas prices)

Graph of Oil and Retail Diesel Prices (Gas prices)

Notes – These prices come from random service stations, though I do try and go to the cheaper ones

Thanks to the Energy Information Administration for the oil prices

Free wheeling in your car

April 28, 2008

I’m a fan of getting that extra mile out of a tank of petrol (well diesel… but ya know), and as such have been known to allow my car to freewheel up to lights… I mean come on… surely freewheeling (despite the illegalness) has to be the most efficient… right?

Well it turns out… NO…

If you take the car out of gear, the engine needs a little fuel so it doesn’t conk out. If you leave it in fuel the idea is that the engine is kept going by the inertia, and so doesn’t need fuel.

So its like this, if you are going to free wheel for a very long way… then it will make sense. If it’s a shorter distance like up to the lights, then leave the car in gear. The engine will actually take energy out of the wheels to keep going, and so use less fuel. It will also slow the car a bit, and so you’ll need less breaks… do the savings ever end?

How much energy in… Cars

March 3, 2008

A query came my way to explain kWh again, and its relevance when it comes to automotive fuels. Well. I hope this explains


So here we go.

kWhs are the most common unit electricity is measure in. For me the easiest way to think about it is to think about light bulbs. If you had ten 100W bulbs, and you left them on for 1 hour, they would have consumed 1000Wh (Watt-hours), or 1kWh (kilo meaning thousand). An old one bar heater is usually a 1kW heater, meaning if it was on for one hour, that would be 1kWh. Finally if you left one 100W bulb on for 10 hours, you would consume 1kWh.


Joules is just another unit that energy is measure in. 1 kWh = 3600kJ (kilo-Joule)


So here is a small table:










1 litre



1 litre



1 litre



1 litre



1 kg




So, to take that in Car mode.  A petrol car that gets 35 miles/gallon would equate to about 0.8 kWh/mile, or 1.29kWh/km.

So driving your car for 1 km, and leaving 21 X 60Watt bulbs lighting for one hour… is about the same.

Or look another way… to drive 1 km takes about 36 seconds. In lighting terms that is equivalent to 2150 X 60watt bulbs… Yes.. your car is equivalent to 2150 light bulbs. Far more if we were to consider the energy efficient type of bulbs!