4 x 4 Australia - - Contents -

FOL­LOW­ING on from Volk­swa­gen’s so-called diesel scan­dal, where de­lib­er­ately in­stalled en­gine soft­ware was found to ‘cheat’ the very strin­gent US tests for NOX ex­haust emis­sions, some other car­mak­ers, in­clud­ing Mit­subishi and Suzuki, have been found to be fudg­ing fu­el­con­sump­tion fig­ures.

Here at 4X4 Aus­tralia we don’t test new 4x4s for emis­sions, but we do test very care­fully for fuel use. What we have no­ticed over the past decade or more is that while manda­tory gov­ern­ment-test fuel fig­ures (stated on the yel­low wind­screen la­bels) have come down pro­gres­sively and quite markedly, real-world fuel con­sump­tion fig­ures, while marginally bet­ter, haven’t im­proved to nearly the same ex­tent.

The other trend we’ve no­ticed here is that the more so­phis­ti­cated the pow­er­train in terms of electronic con­trols, fuel-de­liv­ery sys­tems and gear­box type, the greater the dis­crep­ancy tends to be be­tween the of­fi­cial test fig­ure and the real-world fig­ure.

Pow­er­train en­gi­neers will read­ily ad­mit that when you have very so­phis­ti­cated fuel map­ping, finely op­ti­mised high­pres­sure in­jec­tion (ei­ther petrol or diesel) and au­to­matic gear­boxes with up to nine speeds, it’s not all that hard to tweak the pow­er­train re­sponse to the loads placed on it in the of­fi­cial test. After all, the

of­fi­cial test has a fixed set of ‘driv­ing events’, whose pro­to­cols are well known.

You could ar­gue that op­ti­mis­ing the pow­er­train’s re­sponse to the of­fi­cial test is not cheat­ing, but that’s an­other story. Ei­ther way, our of­fi­cial ADR test, based on a Euro­pean reg­u­la­tion, isn’t par­tic­u­larly in­dica­tive of real-world Aus­tralian con­di­tions, with very low av­er­age speeds (see break­out), so it’s no sur­prise that the of­fi­cial fig­ures are well un­der real-world us­age even with older man­ual pow­er­trains with min­i­mal electronic con­trol.

Own­ers often com­plain that their new 4x4 uses a lot more fuel than what the wind­screen la­bel states, but prob­a­bly fail to re­alise that the la­bel fig­ure is what the car used in the of­fi­cial – and ef­fec­tively the­o­ret­i­cal – test. The man­u­fac­turer is not say­ing this is how much fuel the ve­hi­cle will

use when you drive it in the real world.

So the prob­lem lies not with the ve­hi­cle man­u­fac­turer as such but with a test pro­ce­dure that fails to repli­cate re­al­world con­di­tions. If you are go­ing to blame any­one for the dis­crep­ancy be­tween the of­fi­cial and real-world fig­ures, blame the fed­eral gov­ern­ment’s bu­reau­crats for adopt­ing this par­tic­u­lar test pro­ce­dure, which was de­vised by other bu­reau­crats in Europe.

In­ter­est­ingly, the USA’S En­vi­ron­men­tal Pro­tec­tion Agency uses a com­bi­na­tion of lab­o­ra­tory tests and real-world data to in­form would-be car buy­ers what sort of fuel con­sump­tion they can ex­pect. This gives a more ac­cu­rate fig­ure, but it does come at con­sid­er­able pub­lic cost.

While the fuel con­sump­tion num­bers quoted on the wind­screen la­bel are nor­mally well be­low what you will achieve in the real world, there’s still some rel­a­tiv­ity be­tween them, so they do have some va­lid­ity as a buy­ing tool.

Com­pare Since all man­u­fac­tur­ers op­ti­mise the re­sults, a com­par­i­son be­tween mod­els is valid even if the ac­tual num­bers aren’t re­al­is­tic.

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