Record a meaningful starting point
Before discussing economy, describe your usual trips, speeds, load and fuel use. Separate short urban journeys from longer warm-engine motorway work. A single unusually good dashboard reading is not a reliable baseline for savings.
Use a consistent measurement method over comparable journeys. Keep fuel receipts, distance and the conditions if you want to assess running costs. Tyres, servicing, route and payload can change the result independently of calibration.
Explain the drivability problem
An ECO brief may involve smoother torque delivery or reducing the need for frequent shifts in suitable conditions. Tell us what you want to improve in everyday driving rather than requesting an arbitrary percentage saving.
The calibration still has to suit the engine, gearbox and use. Driving harder after a change can offset any efficiency benefit. We do not guarantee a fixed mpg increase or claim that every vehicle will recover the cost through fuel savings.
Investigate abnormal consumption first
A sudden rise in fuel use, frequent warnings, poor running or an emissions-system fault needs diagnosis. Software should not be sold as the answer before the fault is established. Share servicing and diagnostic information in the enquiry.
For commercial vehicles, explain idle time, payload, driver changes and typical routes. Those factors help keep the assessment grounded in the actual operation rather than a generic fleet promise.
Agree the scope and compare fairly
Ask for the work, required access and agreed checks to be set out before booking. If a vehicle-specific fuel-use expectation is discussed, keep it separate from a guarantee. The best starting information is a healthy vehicle and an honest usage record.
After accepted work, compare like-for-like driving periods using the same method. Note changes in load, weather, tyres or driver. A careful comparison is more useful than assuming every difference came from the remap.