This is an update of a (guest) post I did in December 2012 – I’m planning to keep updating it each year.
These days, most people are aware (often painfully so) of petrol prices being over $2 a litre, and much higher than they were a decade ago. It costs more to run cars than it used to, and consumers’ wallets haven’t really kept up with the cost increase. Unsurprisingly, there’s a heightened awareness about fuel efficiency, which we could also call “fuel economy” to highlight the fact that people are generally more worried about the cost implications.
“Lab tested” fuel efficiency for new vehicles: US trends
The EPA did a fascinating study on fuel efficiency trends in US vehicles manufactured between 1975 and 2013, available at http://www.epa.gov/otaq/
This is what happened to the fuel economy of new American vehicles between 1975 and 2013. Note that this is in “litres per 100 km”, so a lower number means a more efficient car. I’ve calculated the figures for cars, trucks and both of them combined and weighted by production.
US fuel economy standards for new cars stayed the same for more than 20 years, but the Obama administration has begun to tighten them, starting with the 2011 model year, and with major incremental improvements proposed through to 2025.
I think it’s interesting to note, though, that fuel efficiencies started to improve again, well before the tighter CAFE standards began to came into effect. Americans began to shift towards more efficient cars of their own volition. They also started to buy fewer trucks. The market share for these massive vehicles peaked at 48% in the 2004 model year, and has now fallen back to 36%.
“Lab tested” fuel efficiency for new vehicles: New Zealand trends
NZ doesn’t have a long-term data series like the US, but the Ministry of Transport now collects fuel efficiency ratings for vehicles as they enter the fleet. This shows that the light vehicles coming into New Zealand (including cars, vans, light trucks etc) have been getting more efficient. Cars entering the fleet today are at least 10% more efficient than in 2005, on average. You can see the downward trend in fuel use in the graph below. Actually, the graph shows CO2 emissions, but these are directly proportional to the amount of fuel used.
“On Road” fuel efficiency
The data I’ve shown above is lab-tested, and only applies for vehicles entering the fleet. There are a couple of factors to consider when applying it to the real world, and across the entire vehicle fleet. Firstly, cars tend to use more fuel on the road than the lab readings suggest (congestion and air conditioning being the two main culprits). Secondly, the data above is for cars being produced (or imported) in each year, so those fuel economy values can change much quicker than when you’re looking at the total fleet, as for the NZ data. If Priuses were the only new cars sold in New Zealand in 2013, it would still take quite a while before we’d see any noticeable difference to the fuel economy of our entire fleet of 3 million vehicles.
In fact, information from the Ministry of Transport shows that the NZ light vehicle fleet has on-road fuel economy of around 10 L/ 100 km, and this has remained stubbornly flat over the last decade (notwithstanding an apparent drop in 2012, which seems to be down to data issues: the MoT reckon the drop “seems too large to be credible”).
If we take a look at some Australian data, we can see that they’ve actually had no improvements in on-road fuel efficiency in the last fifty years. Australia’s a fair bit hotter than NZ so we can imagine that they took to air conditioning like a shrimp takes to a barbie.Two things to note there – firstly, the MoT data shows “on-road” fuel efficiency, or what our cars have actually achieved on our roads.
So what are the takeaways here? New Zealanders (and Americans) have started buying more fuel-efficient cars thanks to higher fuel prices in the last decade, but the improvement hasn’t been stunning – 10% is nothing to write home about, and there hasn’t been any noticeable effect on how much petrol the overall car fleet uses. In fact, international comparisons make it likely that decades of technological progress have done almost nothing to reduce how much petrol we use. Engines have gotten better, but cars have gotten bigger.
Most of our cars come from Japan, and fortunately they tend to be a bit more efficient than those in the US – not that it’s helped us much. But we’ve jumped on board the SUV bandwagon, and we’ve got a higher proportion of those in our fleet than just about any other country besides the US. We’re also madly in love with big cars like the Holden Commodore and Ford Falcon. The average engine size for NZ cars is a pretty hefty 2.4 litres.