Usually, yes: a larger van will use more fuel than a medium van doing the same job, mainly because it’s heavier and has a bigger frontal area (more wind resistance). But the difference isn’t always “much” — it depends far more on how you load it, where you drive, and which engine and gearbox you choose.
Why big vans tend to drink more
Weight: A large van (e.g. LWB/high-roof) typically has a higher kerbweight and is more likely to be run near its payload limit. More mass means more energy to accelerate and climb hills.
Aerodynamics: Taller, squarer vans cost you on motorways and A-roads. At 60–70mph, drag becomes a big part of fuel use, so high-roof models can be noticeably worse than a low-roof medium van.
Tyres and gearing: Larger vans often run wider tyres and different final-drive ratios, which can nudge consumption up or down depending on spec.
When the gap isn’t as big as you think
If your “medium” van is constantly full and your “large” van is lightly loaded, the larger van can be surprisingly close on fuel — and may even be cheaper overall if it avoids two trips. Modern large vans also often have efficient 2.0–2.2-litre diesels with long gearing that can be decent on steady motorway runs.
Real-world decision tips (new vans)
Match size to the job: Buying a large van “just in case” can cost you every mile if you mostly carry light loads.
Compare like-for-like: When you look at WLTP mpg/CO₂ on new vans, compare the exact body length/roof height, engine output, and auto vs manual — those choices can move the needle as much as “medium vs large”.
Think about zones: If you work in Clean Air Zones, diesel compliance (Euro 6) matters more than size for charges — rules vary by city and can change, so check the local authority site.
If you tell me your typical payload, route (urban vs motorway), and whether you need LWB/high-roof, I can give a more realistic expectation of the fuel difference.
