The Extra Mile

The Extra Mile

Let’s look at one of the fundamental issues of car buying, manual or automatic? Most of us know about using the right gear for the right speed, but it’s not quite as simple as that, as it also depends on the power required from the engine in any given situation. Many drivers take a view that the highest gear is the best one for fuel economy, as long as the engine doesn’t complain, which in steady state cruising at higher speeds is possibly true. But many manual cars, diesels in particular, have very high top gears, chosen to deliver high speed fuel economy; at lower speeds though, in certain situations, such high gears are not the best choice for economy, or even performance. So do today’s automatics handle the business of gear selection for any road speed and situation better than manual transmissions, and can that make them a better choice for economical motoring? 

Fifteen years ago, it would have been hard to settle the debate in favour of the automatic, but with the arrival of multi-ratio seven-, eight- and nine-speed automatics, and twin-clutch automatics that eliminate the power losses of conventional automatics, the evidence suggests this may no longer be the case. With often more ratios to choose from than any manual transmission car, automatics with computerised control of gear selection can beat most humans at the wheel, programmed as they are to automatically choose the best ratio for the job in hand, whatever the speed, power demand and varying road conditions. Of course, some compromises are inevitably involved with the automatics, which could result in continuously changing ratios to suit these constantly varying conditions, possibly to the irritation of the driver. This is compensated for in the programming, but in fact some drivers of automatics do still complain of over-frequent ratio changes, although the refinement of the best multi-ratio automatics these days make frequent ratio changes barely perceptible to the driver. There is also the added bonus of ìSportî transmission settings that focus the ratio changes on performance rather than economy. With the further common option of manual gear change override, often using steering wheel paddles, automatics can offer the best of both worlds for sporting and economy drivers, with the only problem being the cost of the automatic gearbox option when the car is new.  

On top of these benefits, the multiple ratios in a modern automatic enable engineers to specify a top gear ratio that’s most economical for cruising at high speeds (where legal) with the ratio below it instantly available for overtaking at that speed, when power, rather than economy, may become the priority, on account of driver accelerator input. With so many ratios available, the phenomenon sometimes encountered with manual gearboxes of gaps between the gears is also eliminated, although this of course is rarely a problem with diesels, on account of their wide spread of engine torque. But with smaller turbocharged petrol engines, such as the Volkswagen Group 1.0 TSI, the economy and performance potential is considerably enhanced with the seven-speed DSG transmission, as compared with a five-speed manual. Real life fuel consumption figures uncovered for both Audi A3 1.0 TSI and 1.2 TSI Sportbacks show that the S tronic automatic transmission really does deliver better fuel consumption than the five-speed manual transmission. It would be untrue, though, to suggest that better fuel economy can be obtained from all automatics rather than manuals, and it depends largely on how they are driven. But the penalty for ìgoing automaticî is rarely more than a few mpg, and vastly different from times past when all automatics were heavy drinkers.

We cannot conclude without some comments regarding continuously variable transmissions. They are something of a mixed bag, and often specified in petrol/electric hybrids, where they work fairly well, and are seemingly favoured by some manufacturers, yet shunned by others. In theory they offer the perfect gear ratio for any situation, but often frustrate drivers with the selection of low ratios giving high engine speeds when anything more than moderate acceleration is called for. It would be fair to say that they suit gentle, economy-focused drivers rather more than those who drive more for performance, which is possibly why careful hybrid drivers find them acceptable. But it’s down to a matter of personal taste, and the advice must surely be to road test any automatic car in a variety of driving situations before you buy, especially with a CVT gearbox!  

Victor Harman 

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