Motorhome mpg, honestly.

Why the brochure number is not your number

We are not going to give you a "typical motorhome mpg" figure, because there isn't an honest one. A small car-derived camper and a 3.5 tonne coachbuilt are different animals, and two identical base vans can differ a lot once one has a heavy conversion, a roof box and a bike rack. Manufacturer figures are measured on the base vehicle, in a test, without your furniture, water, gas, kit and passengers.

The trip computer is also an estimate. It is useful for spotting trends, but it is worth checking against the pump now and then. The figure that counts is the one you work out from real fill-ups.

What affects motorhome mpg

Speed

This is the biggest one you control. The AA puts numbers on it: driving at 70mph uses up to 9% more fuel than at 60mph and up to 15% more than at 50mph, and 80mph can use up to 25% more than 70mph. Those are general driving figures from the AA, not motorhome-specific ones, but a tall, boxy van pushes more air than a car, so drag matters at least as much for us.

Heavier motorhomes also have lower legal limits. GOV.UK sets motorhomes over 3.05 tonnes maximum unladen weight at 50mph on single carriageways and 60mph on dual carriageways (70mph on motorways). Lighter ones follow car limits. Check where yours sits on GOV.UK before you go.

Weight

The AA's advice is simple: extra weight means extra fuel, so if you do not need it, take it out. In a van that adds up quickly. Full fresh water tanks, a full waste tank, spare gas bottles, tins, tools, a second leisure battery, levelling ramps you never use. We travel with the fresh tank part-full when we know we will be on a site with water, and we empty grey water before a long drive.

Roof boxes, racks and bikes

The AA says roof racks and boxes add to fuel consumption, and suggests packing carefully to reduce drag or taking them off. On a van that is already tall, a roof box or roof-mounted kit sits in clean, fast air. If it is only needed for one trip a year, it is worth the faff of taking it off between trips.

The same thinking applies to anything that sticks out: bikes on the back, awnings left half-wound, solar panels with open fronts. Some of it you need. The point is to know it costs fuel, not to strip the van bare.

Tyres

The AA says under-inflated tyres make a vehicle use more fuel, and to check pressures regularly and before long journeys. The Highway Code goes further on the legal side: tyres must be inflated to the manufacturer's specification for the load being carried, checked when cold. Many vans have a separate, higher pressure for a full load. A converted van is usually near full load all the time, so that is often the figure you want. Check your handbook or the sticker on the door pillar.

Servicing and the engine

The AA also lists regular servicing and the right specification of engine oil. A clogged air filter or dragging brake is not something you will feel at the wheel, but it shows up in the fuel log. Our campervan servicing guide covers the base vehicle side.

Driving style and idling

Smooth driving helps. The AA says idling wastes fuel and the engine warms up more quickly when moving, so do not start it until you are ready to go. It also suggests turning off electrics you do not need, such as the rear heater and demister fan. On a camper, running the engine just to charge the leisure battery is an expensive way to do it; a proper charging setup is better. See campervan electrics for that.

Things that are not your fault

Headwinds, hills, cold mornings, short trips and town traffic all hurt mpg. A week in the Highlands will not look like a week on the M5. That is why tracking over many fill-ups is more useful than any single figure.

How to work out your real mpg

The brim-to-brim method is the most reliable one we know:

1. Fill the tank until the pump clicks off. Do not top up past the click; just be consistent.
2. Note the odometer reading, or reset a trip meter.
3. Drive as normal.
4. Next time, fill to the click again. Note the litres and the miles since last time.
5. Work it out: mpg = miles ÷ (litres ÷ 4.546). There are 4.546 litres in a UK gallon.

A quick example with made-up round numbers to show the sum: 300 miles on 50 litres. 50 ÷ 4.546 is 11.0 gallons, and 300 ÷ 11.0 is about 27.3mpg. Your figure will be your own.

A few things make the log more useful:

• Log every fill, even part-fills, and note when a fill was not to the brim. The next brim fill then covers both.
• Note the trip type: motorway, mountains, towing, roof box on. Patterns jump out after a few months.
• Record the price so you can see cost per mile, which is often more useful than mpg for planning trips.
• Look at the trend, not one tank. A sudden drop across two or three fills is worth a look at tyres and brakes.

Habits that help

None of these will turn a motorhome into a hatchback, but together they make a difference you can see in the log:

• Sit at a steady speed on the motorway and let others pass. Cruise control helps.
• Plan to arrive with low water and empty waste.
• Take the roof box off between trips.
• Check tyre pressures cold, before a long drive, at the loaded figure.
• Look ahead and ease off early rather than braking late.
• Keep up with servicing.

Less fuel also means fewer stops, which helps on quieter rural routes. For trip ideas, see weekend campervan trips.

Questions

What mpg does a motorhome get?

It varies too much by base vehicle, weight and use for one honest figure. Work out your own by brim-to-brim fill-ups over several tanks.

Does a roof box really affect fuel use?

Yes. The AA says roof racks and boxes add to fuel consumption and suggests taking them off when not needed.

What speed is most economical in a motorhome?

Slower is generally better. The AA says 70mph uses up to 9% more fuel than 60mph. Heavier motorhomes also have lower limits on single and dual carriageways.

How do I convert litres to mpg?

Divide litres by 4.546 to get UK gallons, then divide the miles by that number.