Turbo diesel technology is not old, conceptually it is, but there's still a market and a potential for turbo diesel vehicles, therefore it hasn't reached its peak yet. The Hyundai i30 is an apt example of this because in accordance with ADR 81/02 this vehicle can do ~1000km on a tank. However the ADR figures should only be used for comparative purposes only, realistically it would not be that common to replicate these figures in the real world.
We have to remember that the little fuel stickers that are advertised on new cars are only reflective of the ADR test, which is a dyno test. From memory I think the dyno test only uses one average weighted driver (not certain) and is performed with 20-30' air temperature. There will of course be discrepancies between the ADR test conditions and actual real life day to day driving. Lets look at the i30 again, I'm guessing it weighs somewhere around 1300kg give or take. Lets add 3 more 80kg passengers, we've almost added 20% more weight on top of ADR conditions. Add some weathershields and/or windows down to increase aerodynamic drag, tyres not inflated to spec and/or wearing, road friction different to dyno roller, air-con on here and there, today's expected air temp (35' in west), engine wear and/or irregular/improper servicing etc. Therefore there are a large number of factors which will impose a discrepancy between the ADR test conditions and everyday driving conditions making it hard to obtain the figures advertised on the sticker.
Just briefly I'll mention that everybody knows somebody who drove their car on the highway between here and there and only consumed this much fuel which by hand calculations means it averaged this much in fuel economy. Before you call your mate bullshit because he claims that his falcon averaged 6 L/100km on the highway last time he went on holiday, remember that alot of vehicles have are able to sense prolonged highway driving and enter a lean-cruise mode, non-linearity exists in alot of fuel gauges and highway driving often creates more constant driving conditions.
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