Scania : A 25-percent drop in 24 years

We all know that as new truck models are introduced, advances are made in terms of fuel consumption and emissions. But it's only when you take a long-term view that it becomes clear just how much progress is being made. Independently conducted on-road tests that put a 1992 vintage Scania Streamline 143 head-to-head with a New Generation Scania S 500 show this beyond a shadow of a doubt.

Fuel consumption accounts for a significant proportion of running costs for all truck operators. This means that there's considerable impetus to achieve ever higher levels of fuel efficiency. On top of this, there are also initiatives from both the public and private sectors to reduce carbon emissions for environmental reasons.

'Fuel-use per transported tonne is currently the most important factor for 4×2 vehicles in European long-haul operations,' says Henrik Wentzel, a senior engineer at Scania.

Since 2004, new Scania trucks have been equipped with a system for monitoring fuel consumption and emissions. The data produced is read during servicing, meaning that Scania has a relatively good idea how the area has developed over the years.

'When we compare vehicles used in more or less the same way, the statistics show that fuel consumption has dropped by 1.3 percent a year since 2004,' says Wentzel. 'At the same time, nitrogen oxide emissions have dropped significantly and constantly sit under the tough compulsory threshold, which is currently 0.4 g/kWh.'

Rather than guessing about the development over longer periods of time, Scania decided to ask powertrain-testing company AVL to conduct an independent test. The company measured fuel consumption and nitrogen oxide emissions over six identical 140-kilometre test drives of a 25-year-old Streamline 143 and a newly manufactured New Generation Scania S 500.

Both vehicles were designed for timber transport and had 500 hp engines. The older truck had a V8 engine with a displacement of 14 litres, while the new truck had a straight six with a displacement of 13 litres. Despite its smaller size, the new engine was more powerful at all engine speeds.

'We did it this way [using a straight six] because both vehicles reflect typical timber transporters of their day,' says Wentzel.

The test drives took place at the beginning of February 2017. The 143 was in very good condition and was on exhibit at the Scania museum in Södertälje prior to the test. Apart from a necessary update of its tyres, it was effectively in the same mint condition as the S 500. During testing, the vehicles were driven at 85 km/h on the same stretch of Swedish national road 73 south of Stockholm, at the same time, and by the same two drivers. They had the same cargo weight, which gave the new vehicle a small advantage as it was lighter overall.

'The most important effect of the lower curb weight of the new vehicle is that it can transport more timber per transport. This means fewer journeys and thus lower emissions,' says Wentzel.

The drivers were forced to swap between the two vehicles so that the text results wouldn't be influenced by who was driving. The fact that the drivers were - just by chance - father and son, Johan and Lucas Remmert, seemed almost symbolic.

'The biggest difference was the noise level,' says Lucas. 'In the cab of the new truck, it was completely quiet. The gearbox on the R 450 is also extremely quick. It handles cold starts, eats up the hills, and knocks its current competitors out of the park.'

His father Johan agrees. 'Comfort-wise, it's clear that things have become much better,' he says. 'At the same time, though, I got quite nostalgic about the 3-series. It was more like real driving. I'd choose it for a Sunday drive!'

So, what did the test results show? They turned out to be in line with developments since 2004. In the 24 years between the production of the two trucks, fuel consumption fell by about 25 percent. Nitrogen oxide, meanwhile, fell by 95 percent.

'It's confirmation that the improvements that we are gradually introducing produce consistent results over time,' says Wentzel. 'That's the way it is with the development of diesel engines. There's no revolutionary fix for everything, and instead it's all about working hard on the details.'

He points to a long list of factors behind the change. Engines have become more efficient, as well having greater torque and power for their size. Aerodynamics has been improved, semi-automatic gear boxes reduce fuel consumption, rear axle ratios are lower, auxiliaries have improved, and the curb weights are lower.

'This experiment provided a really pleasing result,' Wentzel says. 'Our increased focus on fuel consumption and harmful emissions has given good results.'

Fuel consumption and nitrogen oxide emissions for newly manufactured 2-axle tractor units with semi-trailers

The two vehicles compared

Test-drive results

• The vehicles were test driven at 85 km/h six times on the same 140-km stretch of road
• The new vehicle consumed on average 25% less fuel.
• Emissions of nitrogen oxide (NO) had fallen by 95%.

Factors believed to account for the improvements

• Improved efficiency in the engine's sweet-spot: 6%
• Downsizing of the engine (greater torque and efficiency with a smaller engine): 2-3%
• Improved aerodynamics: 4-8%
• Semi-automatic gearbox with Opticruise and Eco-roll: 4-6%
• Higher rear axle ratio, resulting in lower engine speeds and drag during highway driving: 2-3%
• Improved auxiliaries: 1%
• Lower curb weight enabling higher payloads (5-6%) or fuel savings: 1-2%
• For safety reasons, both vehicles had relatively new and comparable winter tyres. In real life, tyres have also improved.