Over the last few years we’ve seen increasing appearances of ‘eco’ model variants, with various modifications that significantly reduce fuel consumption and CO2 emissions of standard models. Typical costs of such technology are £650 for a SEAT Ibiza 1.2 TDI Ecomotive over a standard Ibiza 1.2 TDI and £835 for a Vauxhall Insignia 2.0 CDTi ecoFLEX over the standard 2.0 CDTi, although some cost premium figures appear to be higher, due to equipment changes.
Sensibly, nearly all eco models wear fuel-saving low rolling resistance tyres, which are a win/win feature, as tyre rolling resistance eats up between 15 and 25 per cent of your fuel, whatever your motoring mix. But most employ a number of other, now familiar, tweaks, some of which (like stop/start) can save fuel in city motoring, but offer insignificant benefits on the open road. Similarly, aerodynamic and higher gearing tweaks often employed offer no gains in urban motoring. But we suspect that drag-reducing lowered suspension and other aerodynamic aids don’t actually save many country motorists much money either. The same goes for higher gearing, which can be a pain in hilly country and may fail to deliver real life gains for many drivers unless they seriously modify their driving techniques. Perhaps it’s time for manufacturers to offer both “City” and “Open Road” eco model variants, each incorporating fuel-saving modifications most relevant to the intended use?
But we now have a nice illustration of where some significant gains do come from, with Vauxhall’s facelifted new Corsa ecoFLEX, where the simple addition of stop/start technology to the CDTi 75 engine costs just £265, and improves the EC Urban fuel consumption from 53.3mpg to 58.9mpg. It allows us to calculate a theoretical “payback” distance to recover the “investment”, which works out at around 22,000 miles which, if reproduced in real life motoring, seems a pretty fair return over perhaps three years of city driving. But the break-even figure is almost 60,000 miles, if your motoring mix is more like the EC combined test cycle, with significant open road motoring when the start/stop benefits have far less effect.
But it’s actually something of a buyer’s jungle out there – because the more powerful and torquier CDTi 95 ecoFLEX stop/start variant is even more economical than the CDTi 75 ecoFLEX stop/start, and only costs another £505. For this you get a huge 8.4mpg boost in the Urban EC test and a 10.1mpg gain in the combined figure, giving payback mileages of under 40,000 miles for the extra dosh and dash of the CDTi 95. Not only that, but the CDTi 95 also drops under the magic 100gm/km CO2 level, giving free London Congestion Zone travel and Vehicle Excise duty, whilst the insurance rating of the 94bhp variant is only one group higher. Just don’t be talked by any salesman into the non stop/start CDTi 95 in sexy SE or SXi trim though, because it comes with wider 16inch tyres on fat alloys and (we suspect) lower gearing that knocks the fuel economy figures by over 20 per cent! It also pushes the insurance up another group, kills the free London motoring, and costs you another £10 a year for your tax disc! Which just shows you how much you need to keep your wits about you, and your Diesel Files data on hand, so you can spot such tempting trim variations that could actually end up costing you serious money!