Fleet
Managing fleet fuel: A guide to reducing costs and improving efficiency
Fuel costs are rarely just about the price at the pump. For fleet managers, the bigger challenge is understanding where money is being lost across everyday operations.
Fleet fuel management is the process of tracking and controlling fuel spend, from where drivers fill up to how efficiently vehicles are used. Done well, it helps fleets identify waste, improve fuel efficiency, and keep costs under control.
One big issue rarely impacts fuel budgets. They leak through small everyday moments: a higher-priced fill-up at an off-network site, unnecessary idling, or a transaction that does not look right.
This guide will explore how to measure fuel efficiency, identify where fleet fuel costs commonly leak, and how to manage fuel and electric vehicle (EV) charging together as your fleet transitions to a mixed-energy future.
What does good fuel economy look like?
In the UK, fleet fuel efficiency is typically measured in miles per gallon (MPG), but the right benchmark depends on vehicle type and usage.
| Vehicle type | Realistic MPG range | Typical annual litres (20,000 miles) |
| Diesel company car | 45–60 MPG | 1,500–2,000 litres |
| Light commercial van | 35–45 MPG | 2,000–2,600 litres |
| Larger van / 3.5t | 28–35 MPG | 2,600–3,200 litres |
| Heavy goods vehicle (HGV) (articulated) | 7–10 MPG | 9,000–13,000 litres |
The most useful comparison is between similar vehicles on similar routes. A van returning 32 MPG may be performing well on demanding routes, while another achieving 40 MPG on lighter journeys may not be. Look for vehicles that consistently perform differently from their peers. That is where there may be an opportunity to investigate.
How to calculate your fleet’s MPG
A single journey or dashboard reading will not always show the full picture. For a more accurate view of fuel efficiency, calculate MPG over several refuels using your actual mileage and fuel usage.
- Record the miles driven since your last refuel.
- Record the litres added when you fill up.
- Divide miles driven by litres used.
- Multiply by 4.546 to convert litres into UK gallons.
MPG formula: miles driven ÷ litres used × 4.546 = MPG
Repeat this over several refuels to get a more reliable average. Fleet managers may need to manually cross-reference information to identify potential issues.
Understanding where your fuel spend goes
A fuel invoice can tell you what you spent, but not always why you spent it. To understand where costs are increasing, fleet managers need visibility into the everyday behaviours and decisions behind each transaction. This includes where drivers refuel, how vehicles are being driven, and how fuel cards are being used.
1. Out-of-network purchasing
Drivers do not always choose where to refuel based on cost alone. Convenient forecourts can sometimes mean paying a higher price per litre or moving outside your preferred network.
Giving drivers access to more suitable fuel sites helps fleets maintain control over spend. The Esso Card™ by WEX gives fleets this flexibility, giving drivers access to 1,400+ Esso sites across the UK.
2. Driver behaviour
How a vehicle is driven has a direct impact on fuel efficiency. Studies by Transport for West Midlands show that driving aggressively or at high speeds can increase fuel consumption by up to 40%, or an average of £520.
Common causes of increased fuel use include:
- Excessive idling
- Harsh acceleration
- Heavy braking
- Speeding
- Unnecessary detours
The good news is that research from the University of Bath and Ashwoods Automotive found that eco-driving techniques can reduce fuel consumption by around 10% on average. However, the impact of driver training can reduce over time, making ongoing visibility into driver behaviour important.
3. Fraud
Not every unusual fuel transaction is fraud, but without the right controls in place, small instances of misuse can quickly increase costs.
Common examples include:
- Using a fuel card for a personal vehicle
- Purchasing non-fuel items
- Sharing fuel cards or PINs
- Unauthorised transactions
Research shows that 19% of motorists are more likely to exaggerate fuel expenses due to the rising cost of living. Manually checking every transaction is not realistic. What matters is having the right controls in place to catch unusual activity early.
Mixed fleets: managing fuel and electricity together
The reality is that most fleet managers are most likely managing electric vehicle (EV) charging and traditional fuel. In the UK, EVs accounted for 23.4% of car registrations and 8.7% of van registrations in 2025, making mixed energy management a growing part of fleet operations.
Fuel transactions, charging apps, home charging claims, and depot costs often sit separately. Bringing this data together helps fleets understand the true cost of running each vehicle.
To understand the true cost of running each vehicle, fleets need to:
Track total energy per vehicle: Combine fuel and charging costs to understand the true running cost of each vehicle.
Measure cost per mile: MPG works for fuel, but cost per mile allows you to compare petrol, diesel, hybrid, and electric vehicles.
Bring billing together: Manage fuel and charging data in one place to simplify reporting, identify discrepancies between claimed mileage and fuel card spend, and spot opportunities to reduce costs.
Improving fleet fuel management with WEX
Keeping fuel costs under control starts with understanding what is happening across your fleet, from where drivers are refuelling to how vehicles are being used. The more visibility you have into everyday fuel decisions, the easier it becomes to identify inefficiencies, manage spend, and make informed changes.
WEX’s fleet solutions help bring this information together, giving fleets greater visibility across fuel, vehicle and energy data. This can support day-to-day fuel management across petrol, diesel, electric and mixed-energy fleets.
Take charge of your fuel and charging spend with WEX fleet cards, and make it easier to manage costs across your fleet.
