In the second instalment of our monthly fuel saving series below, our expert truck tester debunks the myth that driving faster gets the job done quicker.
So, how did you go on last month’s challenge – reducing the number of times you stop? Let us know . . .
One of the biggest myths in road transport is that driving faster gets the job done significantly quicker.
In reality, it often gets the fuel bill up much faster than it gets the truck to its destination.
A number of years ago Scania conducted a fuel economy test between Melbourne and Sydney. The only significant change was reducing maximum cruising speed by 5km/h.
The result? The truck used around 45 litres less fuel for the trip. For a vehicle making five return trips a week, that equated to roughly $15,000 a year in fuel savings at the diesel prices of the time. Yet the trip took only about 45 minutes longer.
That’s a trade-off many operators would happily take.
Speed Tip #1: Speed limits are maximums, not your minimum
The most accurate forecast trip times are calculated by operators based on experience with the route, not a computer calculated time based on speed limits and assumptions that drivers will pull out all stops to maintain the signposted speed.
Provided you are driving with your new anticipation skills finely tuned, you will find that operating just below the speed limit will have almost no impact on your trip time, especially if you are operating in metro or regional operations.
Long-haul operations are a different matter, but it rarely upsets a customer if anticipated trip times are already calculated with experience in pulling back top speeds.
Your speed at any time should be determined by traffic and road conditions first, speed limits second.
Fuel burn increases exponentially to increases in speed. To increase your speed by 5 per cent you need to burn a lot more than 5 per cent extra fuel.
The converse is true. Reducing speed by 5 per cent saves more than 5 per cent of fuel. An additional benefit is a long term one.
At some point you have to get rid of that energy and stop the truck. Brakes, tyres and in fact all running gear benefits from less speed stress.
Speed Tip #2: Slow down slower
Think back to last month’s discussion about momentum.
Every time you need to brake heavily, you’re usually paying the price for something that happened 10 or 15 seconds earlier.
Maybe you were following too closely, maybe you weren’t reading the traffic lights. Maybe you didn’t notice congestion developing ahead.
The harder you have to slow down, the more momentum you’ve wasted. Good drivers don’t simply slow down. They slow down gradually.
They come off the throttle early, allow rolling resistance and aerodynamics to do some of the work, and use the truck’s natural deceleration before resorting to the braking systems.
The truck remains balanced, the ride is smoother and fuel consumption decreases.
You have the best seat in the house for forward vision, so lift your view and react early.
A key point which we’ll cover in more detail next session – Stepping off the throttle reduces the fuel flow to zero. That’s right. Coasting drops the engine to idle speed, where it’s still using fuel. But no throttle, means no fuel.
Speed Tip #3: Take the torque off early
Most drivers travel the same roads every day. They know where the hills are and they know what’s on the other side. Yet many still attack every rise as though they’re qualifying for Bathurst.
One of the most effective fuel-saving techniques is backing off the throttle as you approach the crest of a hill.
Last month I noted a fuel test I drove with Volvo’s Paul Munro where he used 13 per cent less fuel by letting speed gently bleed away near the top of a rise.
Instead of demanding maximum power all the way to the crest, he’d ease off the torque, roll over the top at perhaps 80 to 85km/h and allow gravity to restore the speed on the downhill side. Some of the latest trucks recognise this fuel saving technique in their software.
With a GPS enabled route system, the truck knows the terrain ahead and the detail of each hill. It will automatically reduce torque near a crest and allow speed to build up on the other side.
Unfortunately, some early systems were coded for Europe – not for B-double operation. They blindly cut back the torque as the prime mover rolled over the peak, but as the A-trailer was still heading uphill, the rig slowed down dramatically.
Disciplined and professional drivers – like you, are best equipped to manage torque and boost fuel efficiency. Overall, this one simple change in driving technique alone can deliver a massive saving.
Speed Tip #4: More throttle doesn’t always mean more acceleration
Drivers of older trucks need to be particularly aware of this. Many older engines can be over-fuelled, and pressing harder on the throttle pedal just sends more unburnt fuel into the exhaust system.
In simple terms, pushing the throttle harder doesn’t necessarily make the truck accelerate any faster. It simply injects more fuel into the engine than is required.
Modern electronically managed engines are far better at preventing this, but there are still plenty of older trucks working hard around Australia.
But whatever the age of your truck, when more throttle makes no difference, there’s simply no point in pressing it any harder. Time to drop a split, or a full gear – or two.
You might have a steel capped boot on your right foot, but you can still ‘feel’ the torque increasing as you press the throttle. It’s not a light switch – smooth, progressive throttle application is almost always more efficient.
Speed Tip #5: Watch the idle time
This one surprises many drivers.
Not so long ago I used to quote about five dollars per hour of idle cost. With today’s fuel prices, that figure is considerably higher. One hour here and there may not seem significant, but over weeks, months and years, unnecessary idling can consume thousands of litres of diesel.
If you’re stopped for an extended period and operational requirements allow it, shut down and save fuel. Modern engines can handle it.
Summary
Speed adaptation isn’t about driving slowly. It’s about driving intelligently. Good drivers understand that every road, every hill and every traffic situation requires a slightly different approach.
As mentioned already, the throttle pedal is a precision control. Every time you flex your right foot, several things happen under the bonnet, and it’s not a simple as squirting more fuel into each cylinder.
And milliseconds later – off you go . . .
The smoother and more deliberate you are with managing the throttle, the less fuel you’ll burn. Remember that reducing fuel consumption isn’t usually about one big change. It’s about dozens of small decisions made during every trip.
The drivers who consistently achieve the best fuel economy figures aren’t necessarily the ones with the newest trucks and latest engine tech. They’re the ones who understand how to adapt their speed to the conditions and use only as much throttle as they genuinely need.
So – things to focus on this month:
• Back off a bit – Save a lot
• Slow down slower
• Ease back on the torque approaching hill crests
• Eliminate unnecessary idle time
Next month we’ll look at the braking systems already working for you every time you lift your foot off the throttle – and why the service brakes should often be your last choice, not your first.
Extracted in full from: https://bigrigs.com.au/2026/08/13/fuel-smart-series-speed-adaptation-and-throttle-control/
