How much fuel does a remap save? Data on cars, trucks and HGVs
It depends on the engine, the load and the use, but the data collected over more than ten years on cars and heavy vehicles are consistent: on turbodiesels a well-calibrated increase in the torque curve means lower consumption at the same performance. Here are the numbers, with the assumptions behind them.
Why a remap lowers consumption
A diesel engine consumes in proportion to how much fuel it injects to produce the torque the driver asks for. After an eco remap or a well-made Stage 1, the torque available at low and medium revs rises by 20-30%: to keep the same pace you use less throttle, shift earlier and run the engine in a zone with better efficiency (more boost, optimised timing, adequate rail pressure). The saving does not come from “taking fuel away”, but from producing the same energy with less waste.
It holds for the same driving style. If the extra torque is used to go faster, consumption rises. The figures below are measured on comparable routes and loads before and after.
Turbodiesel cars
On Euro 4-6 turbodiesel cars an increase in the torque curve comes with a fuel saving of up to 25% at the same performance, noticeable from the first fill-up. The average we see in mixed use is around 10%; 25% is reached on the motorway at constant speed, where the taller gear and lower revs count most. On turbo petrol engines the saving is smaller (3-8%) and on naturally aspirated engines negligible.
Trucks and HGVs: fleet table
On a reference mileage of 120,000 km/year savings range between 5% and 20%, with average measured values around 13%. With a base consumption of 33 l/100 km and diesel at €1.60/l, one truck spends about €63,000 a year on fuel:
| Saving | Litres/year saved | Euro/year per truck | Fleet of 10 trucks |
|---|---|---|---|
| 5% | 1,980 l | ≈ €3,170 | ≈ €31,700 |
| 10% | 3,960 l | ≈ €6,340 | ≈ €63,400 |
| 13% (measured average) | 5,150 l | ≈ €8,240 | ≈ €82,400 |
| 20% | 7,920 l | ≈ €12,670 | ≈ €126,700 |
Even at just 5% you exceed €3,000 a year per truck, more than the cost of the job. On heavy vehicles the calibration is done to reduce consumption, not to increase speed: the limiter stays at 90 km/h and the extra torque is used to hold the gear uphill without downshifting.
When there is no saving
- Engine with problems: clogged DPF, coated EGR, worn injectors or a leaking turbo. Repair first (or deal with the DPF and theEGR), then calibrate.
- Generic map not adapted to the software version and the vehicle: it can mean more smoke and higher consumption. See how an ECU map really works.
- Driving style: extra torque spent on acceleration cancels the gain.
- Naturally aspirated petrol and hybrids: minimal margin, not the right use case.
How it is achieved
Reading the original file via OBD or bench, custom calibration of requested torque, limiters, injection, boost and rail pressure, timing; verification with road or dyno logs; backup always delivered. For the technical detail read ECU reprogramming: more torque, less fuel; for remote work, workshops upload the read file to TuningBot.
Frequently asked questions
Is the saving guaranteed?
No: it is a statistical range. On turbodiesels in good condition the saving is almost always there; how much depends on route, load and driving.
Can I have more power and lower consumption together?
Yes, it is the same job: the extra torque is available, but you only save if you drive as before.
How much does the job cost on a truck?
It depends on the vehicle and the reading method; for fleets we quote per truck and by number of vehicles. Typical payback is within the first year.
Do I need to modify the DPF or AdBlue to save fuel?
No. The eco calibration works on the torque and injection maps; the after-treatment systems stay functional, unless otherwise requested where lawful.
How do you measure the saving?
Comparison of average consumption on comparable routes and loads before and after, using on-board computer or fleet telematics data.
Want an estimate for your fleet?
Send us model, engine and annual mileage: we give you the expected litres and euros saved, and the cost of the job per vehicle.