Fuel consumption today vs two decades ago

It is almost impossible for any online car review to mention the miserly fuel consumption of their latest steed without some illiterate person making disparaging comments, implying that their Toyota/Opel/VW of twenty years ago was almost as good anyway. (See Polo Blue Motion review for an example).

What seems to be invariably forgotten/ignored in the comparison is that their old car weighed 30%-60% less - reason being the added safety equipment today.  Crash that old car at 60km/h and you are guaranteed severe injuries, if not death, whereas the modern, 4 or 5 star Euro NCAP car would let you off almost unscathed.  Assuming, of course, that you have the - surprisingly rare - ability to buckle the seat belt.  No wonder airlines feel the need to still educate us on their use today...

Another culprit is the SI unit for fuel consumption - l/100km.  A consumption of 5.1 does not sound much better than 6.3, whereas it is, in fact, a significant improvement, that can be further confused by mathematics: If car A has a consumption of 5.1 l/100km compared to car B with 6.3 l/100km, car A's consumption is 19% less than car B, but car B consumes almost 24% more fuel than car A.

Lastly, the consumption claims are always compared "on the open road" - where we spend very little time.  Compare those identical cars in congested traffic, and a different picture will emerge.

I happen to have the figures for a few cars from 1998 (only 13 years ago, but still proving my point). The modern competitors have been chose to match power and acceleration, not engine size.  The figures for 1998 are from an auto motor und sport article (1998) and the 2011 figures are from the german car websites.

Car	0-100 km/h	Power	ECE/EU urban	ECE/EU open road	% increase from open road to urban	Euro NCAP
1998 Alfa Romeo 156 2.5 V6 24V	7.7s	140kW	16.5 l/100km	8.4 l/100km	96%	N/A (YouTube videos look bad)
2011 Alfa Romeo 159 1.8 TBi 16V 146kW	7.7s	147kW	11.8 l/100km	6 l/100km	97%	*****
1998 Audi A4 2.8	7.1s	142kW	13.6 l/100km	7.0 l/100km	94%	***
2011 Audi A4 2.0T	6.9s	155kW	8.3 l/100km	5.3 l/100km	57%	*****
1998 BMW 328i	7.6s	142kW	12.5 l/100km	7.0 l/100km	79%	****
2011 BMW 325i	6.7s	160kW	9.8 l/100km	5.7 l/100km	42%	*****
1998 Mercedes C280 sport	7.8s	145kW	14.8 l/100km	7.4 l/100km	100%	****
2011 Mercedes C250 BlueEFFICIENCY (Auto)	7.2s	150kW	9 l/100km	5.6 l/100km	61%	*****

So, all the modern cars are safer.  All the modern cars are faster (except Alfa, as fast).  All the modern cars use substantially less fuel on the open road.  All the modern cars use considerably less fuel in urban conditions.  All the modern cars (except Alfa) has a much smaller increase when used in urban conditions than the old cars.

So, your uncle's 20 year old Opel can reach Durbs using only 25% more petrol, but try to commute from Fourways to Sandton every day...