The Clean Green Cars web site is worth a look for people interested in, as the name suggests, cleaner, greener cars. This week it has come up with a couple of very interesting stories.

First, it has published tables combining figures for CO2 emissions with UK sales figures, giving averages across ranges – presumably the kind of calculation that will be deployed by government regulators as they push for lower fleet averages.

The European Commission has pondered imposing an average of 130g/km, and CGC's data reveals exactly how many manufacturers would limbo under this limit today. In short, none.

Top of the table is Fiat with an average of about 142g/km, marginally worse than last year's 140g/km. Makers known for small cars – Peugeot, Daihatsu and Citroen – follow, with Toyota next, boasting an impressive 149g/km, down from 155g/km in 2006. The decision to split Lexus into a separate brand helps of course, with its hybrid models only managing to trim emissions down to 197g/km, from 207g/km last year.

Unsurprisingly the bottom of the table is home to luxury and sports marques Porsche, Aston Martin, Maserati, Rolls-Royce, Maybach and Bentley, with Lamborghini bringing up the rear with a fleet average of 430g/km. Oddly, Ferrari is missing from the list, but evidently it hasn't been lumped under the Fiat total.

Meanwhile CGC has uncovered a loophole in the London Congestion Charge rules. Rules that are, of course, a little odd in places. Apparently anyone can register their car as a private hire vehicle (or minicab), and with a relatively small outlay and inconvenience (about £150 per year and MoTs at six-monthly intervals) you can duck the £8 daily charge (amounting to more than £2,000 per annum for daily London drivers).

Obviously the rich like to stay rich by watching the pennies, judging from some of the vehicles that are currently registered as minicabs: an Aston Martin DB7, eight Mercedes-Benz SL sports cars, and a Jaguar XK, among others – which are not exactly ideal wheels for making money on the meter.

Not that the Clean Green Cars investigative journalists are all that and a bag of chips. (Nor are the BBC's for that matter.) They seem to think it's remarkable that 31 Bentleys and 52 Range Rovers have been registered as vehicles for hire, suggesting that this cannot possibly be pukka. To which we can only say, hang around streets near Leicester Square next time there's a big-name Hollywood première, and count the luxo limos delivering celebs – each with a dayglo minicab badge in the window. There's plenty of excess in evidence but not necessarily any Congestion Charge cheating.

“A Maybach costs £5 per mile in depreciation before you factor in fuel (around 10 mpg in central London) and servicing,” CGC wails, adding, “How exactly do you run a Maybach as a private hire car when a London taxi charges less than £3 per mile?” Well, the maths is quite simple really. You charge £300 an hour with a minimum fee of £1,200.

And while we're poking CGC with a stick, don't bother checking out its car reviews. There's not much green about the judgements on offer – in fact you'll find exactly the same write-ups over at the petrol-headed Fifth Gear web site. Both sites have been put together by the same contract publishing company.

Passing off something for other than what it really is? Pot, go give the kettle a scrub.