Toyota Prius proves a gas guzzler in a race with the BMW 520d

The Toyota hybrid is hailed as an eco-paragon, so how does it fare against a big BMW? To find out our correspondents go on a run to Geneva.

The Prius, like the iPod, is more than a piece of clever technology. It symbolises something bigger – a responsible attitude, a healthier way of living. Toyota has sold more than a million examples of the car since launching it in 1997 and it has attracted a worldwide following led by Leonardo DiCaprio, Cameron Diaz and much of the rest of Hollywood.

It’s classified by the American government as the “most fuel-efficient car sold in the US” and this seal of official approval is reflected in a special status that the Prius and other hybrids enjoy over conventionally powered cars.

For example, you can drive a Prius in American “high occupancy vehicle lanes” – designed for vehicles carrying passengers – even if there’s nobody else in the car. In Britain the Prius has had a similar boost. You can enter the central London congestion zone without paying the usual £8-a-day charge. For road tax purposes it’s classed as an “alternative fuel vehicle” so you pay less tax than you would for a conventional car that produces the same emissions. Road tax is just £15 a year and in last Wednesday’s budget, Alistair Darling, the chancellor, renewed his commitment to preferential treatment for hybrids. Plus, if you drive a Prius as a company car it enjoys a 3% discount (until April) compared with the tax on other cars producing identical amounts of carbon dioxide.

But are transport and tax planners – here and in the US – being fair to the people who drive conventional cars? The official fuel consumption figure for the Prius – supplied by Toyota itself – is 65.7mpg in mixed motoring. That’s a claim not supported by many of the letter writers to The Sunday Times who say they get nearer to 50mpg. If our readers are right and the official figure is wrong it has important implications, not least of which is that people driving frugal diesels are getting a raw deal.

To find out we set a challenge: to drive a Prius to Geneva using motorways and town driving. The direct route is 460 miles but we drove almost 100 miles further to give the Prius the advantage of running in urban conditions where its petrol-electric drivetrain comes into its own.

We took along a conventionally powered car – a diesel BMW executive saloon – for comparison and drove both cars an identical number of miles (545).

The BMW doesn’t have the external look of a green car and you don’t get the same self-righteous glow when you are driving it. There’s no hybrid badge on the back; in fact, because it’s the entry level car of the 5-series many buyers opt for “badge delete” so they don’t show other motorists they went for the cheapest option at £27,190.

But it does have a few tricks up its sleeve to conserve fuel. Efficient Dynamics, as BMW refers to its fuel-saving technology, is a term coined by Bavarian marketing men for refinements that taken on their own are nothing spectacular but together improve fuel economy. Rather than Toyota’s big idea – a radically different system of powering a car using a petrol-electric drivetrain – BMW has sunk its research effort into lots of less radical things.

The most important of these is the new four-cylinder engine. It’s available in the 3-series but here it’s perfectly at home in the bigger 5-series saloon where it generates a surprising 177bhp. Surprising because it’s only 1995cc and it sips fuel. Combined fuel consumption is – officially – 55.4mpg and emissions are 136g/km, which puts it into tax band C. That’s respectable for its size, especially when you consider that 13 cabinet ministers are driven in cars with tax band F – the second highest bracket – and one, we don’t know who, has a band G car.

Various other features of the new BMW contribute to its frugality. It’s got better aerodynamics to reduce drag; low rolling resistance tyres; and a dashboard gauge that gives you a continuous fuel consumption readout so you know when to change gear.

So how does it drive? Well, much like any other executive saloon, actually. Its six-speed manual transmission needs quite a lot of work but if you are concerned about fuel economy then it’s a small price to pay for the extra 5mpg that it gains over the automatic version.

The 520d is not startlingly quick, but it will reach 62mph in 8.3sec. As for the claimed top speed of 144mph, I didn’t get the chance to test it to its limit but I think it would have struggled to reach that. Nonetheless, it cruised happily at the French autoroute limit (dry conditions) of 78mph towards the champagne region.

As I did so, I noted with slight satisfaction that Jason was having difficulty keeping up, so I cut my speed. Had I been really serious about saving fuel I could have also switched off the air-conditioning and the stereo but I was more concerned about making this a real-world test.

Stuck in rush-hour traffic in Reims, fuel consumption dropped to an average of about 40mpg – still not bad when you consider the size of the car. BMW has fitted a diesel particulate filter, enabling the car to meet ever more stringent European Union limits on emissions. Another feature designed to cut running costs is the brake regenerative system – similar to that in the Prius – which recovers energy from braking to recharge the battery and help power the electrical systems. To what extent this is a genuinely eco-friendly feature and how much a conscience salver is impossible to tell when you’re driving.

But you can’t argue with the end result. Approaching Switzerland I felt confident of beating Jason. The computer was telling me that, for the journey as a whole, I had averaged more than 50mpg. The test had taken us along just over 200 miles of autoroute, about 200 miles of B roads, including winding ascents and descents in Switzerland, and 100 miles of urban driving.

Before we set off, Jason and I filled our tanks to the brim. At the end of the journey, at a filling station in Geneva, we filled them again to find out how much fuel we’d used. The BMW had done the journey on 49 litres (just over two-thirds of a 70-litre tank). Jason had . . . well, I’ll let him tell his own story.

The Prius is not a car you can easily get excited about, at least on a purely visual basis. But this test was not about kerb appeal, it was about pump avoidance. The Prius was designed with a straightforward goal in mind – to create a five-seat family hatchback that was as good on fuel as a 2+2 supermini. Straightforward aims are often notoriously difficult to achieve.

Toyota’s big idea was to use hybrid power. In other words, two forms of propulsion. The bulk of that power comes from a 1.5 litre petrol engine producing just 77bhp. That kind of power may be able to keep the Prius cruising along but is hardly enough to ensure decent acceleration. So added to that comes a battery-powered electric motor generating the equivalent of a further 67bhp and a thumping great 295 lb ft of torque.

There’s no need to plug the Prius into an electric socket to keep the batteries topped up as this is done every time the car brakes, and there is trickle charging by the petrol engine while driving normally. The result of lumping together these two sources of power is a car that can reach 62mph from standstill in less than 11sec and reach 106mph flat out, hardly dragstrip quick and slower than the BMW, but still respectable.

Toyota was obsessive about saving weight in the Prius; at just 2,921lb it is 573lb lighter than the BMW 520d, surely a factor that will pay dividends at the pumps.

Clever power and a light kerb weight stand the Prius in good stead but it’s the car’s incredibly low drag coefficient that may just tip the scales in my favour when it comes to long motorway stretches at higher speeds. As slippery as a campaign manager discussing political donations, the Prius should take less energy than the BMW to maintain a constant cruising speed.

No sooner had we left the offices of The Sunday Times in London than my eyes locked limpet-like on the trip computer readout that tells you how many mpg you are achieving. This was to become my obsession over the next 545 miles as I battled to nudge the Prius into performing somewhere close to Toyota’s claim of 65mpg-plus motoring.

By the time we reached the Channel tunnel the display revealed that I had averaged 55mpg. Hopefully things would improve on the long, uninterrupted roads in France. They didn’t – despite the fact that I didn’t use the air-conditioning and avoided turning on the stereo in an effort to conserve power.

To break the boredom of constantly looking at the trip computer I pressed the throttle into the carpet for a few seconds, but seeing the fuel consumption suddenly dip to less than 10mpg I backed off. When we stopped in Reims neither Nick nor I was willing to declare our average fuel economy figures. I interpreted his reticence as a sign of my upcoming victory.

The next day it became clear my Prius did not like motorways, at least not at 75mph into a headwind. My trip meter informed me I was now averaging about 45mpg; the Prius was not going to make it to Geneva on just one tank.

I took the precaution of buying a 10-litre can and filling it with petrol. Sure enough, the dashboard soon informed me the fuel tank was empty, the petrol engine stopped and for two surreal miles I coasted along on battery power. Only when I approached a long steep uphill stretch did I finally drift to a halt. As I filled the tank I consoled myself with my last chocolate bar.

Coasting down the mountain into Geneva my Prius averaged 99.9mpg for a full 10 minutes. It was the highlight of my journey and improved my overall average fuel economy by a full 2mpg. But it was not enough. For all my defensive driving, slippery bodywork and hybrid technology, my average fuel consumption was 48.1mpg. I’d lost to a Beemer and I was disappointed; I had never driven so slowly or carefully for so long in my life. I’m considering buying a V8 Range Rover and opening my own oil well in protest.

Model BMW 520d SE
Engine 1995cc, four cylinders
Power 177bhp @ 4000rpm
Torque 258 lb ft @ 1750rpm
Transmission Six-speed manual
Official fuel/CO2 55.4mpg / 136g/km
Performance 0-62mph: 8.3sec
Top speed 144mph
Road tax band C (£115)
Price £27,190
Fuel used on test 10.84 gallons (50.3mpg)
Fuel cost £54.19 (diesel)

Model Toyota Prius T Spirit
Engine 1497cc, four cylinders
Electric motor 50kW/67bhp
Power 77bhp @ 5000rpm
Torque 295 lb ft (motor) 85 lb ft (engine)
Transmission CVT automatic
Official fuel/CO2 65.7mpg / 104g/km
Performance 0-62mph: 10.9sec
Top speed 106mph
Road tax band B (£15, alternative fuel)
Price £20,677
Fuel used on test 11.34 gallons (48.1mpg)
Fuel cost £54.64 (petrol)

Are you crazy? If you think deisels cost a lot for spare parts, you have never owned a gasoline engine. A plug in car is fine for commuter driving, low range, no issues with long recharges. However the hybrid stuff is just a joke.

A second engine, combined with the batteries etc, is more costly and environmentally unfriendly to produce. Diesel is a far better option for MPG and environmental friendliness than any of the hybrids.

I have no issue with a true plug in car, if they can get one out that can go 300-400 miles on a single charge at 75 mph and recharge fully in 5-10 minutes.. and not be the size of a shoebox. When they do that they’ll be more than a niche vehicle.

The hybrid nonsense is just that. Even if you wanted to go hybrid, diesel electric hybrid engines are far more efficient than any gasoline hybrid can be. More BTU per gallon in the fuel, and higher compression ratios of deisel mean better fuel economy, period. There is a reason Diesel does the heavy lifting.

Nope, not crazy -- you did READ what I said? I said Diesels are only really worth it if you drive more than 60 to 75 miles per day — as they cost a lot in spare parts. Any lesser than that, they’re not as cost-effective. -- Diesel parts are comparatively more expensive than gasoline engine parts.

If you drive only about 20 miles a day then it's not worth it having a diesel. If you drive more than 60~75, yeah, it is worth it -- any more than that and a diesel is much, much more wallet-friendly.

I didn't say anything about hybrids at all -- I'm just comparing a plain gasoline engine with a plain diesel engine

Finally, the plug-in cars, as I said, are GREAT for city driving. If your commute consists of just bumper to bumper traffic of 30 miles each way, then yes, an electric car is worth it. If you want a vehicle that goes on the interstate and takes you from Boston to NY, then no, an electric car does not make sense.

Maintenance on a diesel is generally less complex, but more frequent. A diesel should have an oil change every 5,000kms and an oil filter every 10,000kms. A typical petrol will require an oil change at 10,000kms with the filter at 20,000kms, and sparkplugs are usually required along with the filter change. Major service items like diesel injectors, fuel pump etc typically require servicing every 100,000kms. Other maintenance items like transmission oil, air filters etc... are independent of engine type and have the same service interval.

If you do your own lube and oil changes, a diesel will generally work out cheaper but more frequent. If you pay for your minor services, the higher frequency of the diesel services will generally cost more than the less frequent but more costly petrol services. This is a generalisation and will differ for different makes and models.

The design parameters of a diesel engine result in it having a longer life between rebuilds. Generally, a diesel will run up some 350,000 kms before requiring a rebuild (provided it has been well maintained) whereas a petrol may require a rebuild at 250,000 kms. While a diesel may take longer between rebuilds, a petrol is cheaper to overhaul so in the long run it works out about even if you plan on using it a lot.

Finally -- all of what I said is about diesel engines NOW -- I do agree that diesel technology is improving significantly and soon, maybe in the next couple of years, diesels will make far more economical sense than petrols for any user except formula 1 drivers.

Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.