Economy – can the latest small engines deliver?

Posted on March 23rd, 2012 by Rob Marshall

With the latest crop of the high efficiency engines arriving on the market, I find myself becoming increasingly concerned by the promises of high frugality that are not being delivered to the average user. As I have highlighted before, many motorists have become frustrated by the Official Combined fuel consumption figures stated for their new or nearly-new cars being unachievable during reasonable everyday use.

Yet, when the guide was issued, even new car testers emphasised that the figures should be treated as such and not be taken as read. However, the black-and-white presence of miles-per-gallon stats creates friction, when they are almost impossible to meet in daily motoring, and I have heard of several cases of new car owners returning to their dealerships, questioning why only 45mpg is achieved against a stated 65+mpg on the Official Combined cycle.

With car manufacturers placing so much focus on fuel economy figures, resulting in many of them trying to better their rivals at every juncture, more and more small-capacity, high-output power-plants have been developed. Units, such as Ford’s 1.0-litre Ecoboost and Fiat’s 875cc TwinAir and even Peugeot/Citroen’s latest diesel hybrid models, are presenting laboratory-generated MPG figures that go through the roof, making it even less likely that the consumer can achieve consumption close to the theoretical figures in real-time.

Yet, the expectation of a small engine to deliver performance figures that match larger capacity units brings additional complications, in that the smaller unit is not going to be as full-throttle efficient as larger engine alternatives, something that is not fully realised within the secrecy of a sealed laboratory. Therefore, a smaller engine that is driven hard is unlikely to be as frugal as a larger engine that is driven gently.

Since high-output small capacity motors started to replace larger engines directly, approximately seven years ago, they have tended to be less reliable than the larger-capacity units. In my experience, even when examining the same model from the same manufacturer, the smaller (often diesel) engine tends to be less reliable than the larger-capacity unit offered further up the range. Naturally, the situation is not helped by extended service intervals, especially in relation to engine oil drain services, and hard-working smaller-capacity engines tend to require more careful management.

Should you be looking to buy one of the latest small-engined petrol or diesel cars, treat the salesman’s quotation of fuel consumption figures with a degree of caution. Take the car for an extended test-drive that involves a cold start and check the car’s MPG readout (should it have an on-board computer) upon your return. Furthermore, if your personal motoring involves many lengthy A-road or motorway runs, consider ‘upgrading’ to a larger engine – ironically, it could become the more economical choice.

Economy – can the latest small engines deliver?