Which cars guzzle the most fuel?

If you own an SUV, you're paying a hefty premium in fuel compared with owners of regular cars of similar sizes.

Which? research shows that all classes of SUV - compact, small, mid-size and large - have significantly poorer fuel economy on average than cars of around the same size.

• Large SUV drivers spend £409 more on fuel each year than large estate drivers.
• Medium-size SUV owners pay £199 more a year for fuel on average than medium estate car owners.
• Even small SUV owners have to pay £154 more a year than small car owners.

If you own your SUV for four years, that's a huge amount extra in fuel you'll be paying - as much as £1,600 more, in the case of large SUV owners.

We've compared each size of SUV to regular cars of a similar size - see the results below. We also reveal how you can cut your fuel costs, whatever car you drive.

Our expert lab tests independently verify each car's fuel efficiency, so you can trust you'll save on fuel costs with one of our best cars.

Compact SUV vs small car fuel costs

They may look beefy, but compact SUVs really are a similar size to small cars. Both the UK's best-selling small car, the Ford Fiesta, and the Nissan Juke compact SUV are around 4m long and 1.9m wide. Though the Juke is around 9cm taller.

Your choice of fuel is important. Small diesel car owners pay the least overall (£876 annually; £172 less than petrol small car owners). Diesel compact SUV owners pay around £250 less annually on average than their petrol counterparts.

However, diesel is in the docks due to emissions scandals and high NOx levels. But that doesn't mean you can't find cleaner cars among them - see diesel cars that produce the most and least NOx.

• The compact SUV class includes models such as the Renault Captur and Audi Q2.
• Small cars includes the Ford Fiesta, as well as the seventh best-seller in the UK, the Volkswagen Polo, and the Honda Jazz.

Small SUV vs medium car

The difference in fuel costs grows as cars get larger.

Choosing a diesel SUV is no guarantee of narrowing this cost difference. In fact, our data shows that, compared to compact SUVs vs small cars, there's a larger difference between what a small diesel SUV owner pays compared to medium diesel car owners.

Although the overall cost of diesel fuel will be lower compared to petrol, as diesel cars are, on average, more economical.

Owners of medium cars drive on average 9,700 miles a year - identical to the cross-class average we've used for comparison purposes.

• The small SUV class includes the Dacia Duster, Volvo XC40 and BMW X1.
• The medium car class is home to models including the Honda Civic and the UK's number three best-seller, the VW Golf.

Mid-size SUV vs large car vs medium estate vs mid-size people carrier

The mid-size SUV class includes the UK's best-selling SUV, the Nissan Qashqai.

Interestingly, mid-size estate owners pay a little less on average for fuel a year than comparable (not SUV) car classes - £1,077 versus £1,100.

• The mid-size SUV class includes the Peugeot 3008 and Kia Sportage
• Large cars includes the Audi A4 and Skoda Octavia
• Medium estates the Mini Clubman and Mercedes-Benz CLA Shooting Brake
• Compact/mid-size people carriers the Vauxhall Zafira and Citroen C4 Picasso.

Large SUV vs large estate vs large people carrier

Driving some of the biggest cars on the road, large SUV owners are splurging out a gigantic £409 premium on average over similar-sized cars in other classes. They burn through £1,561 in fuel costs over the course of a year.

To the chagrin of large SUV owners, drivers of large estates and large people carriers enjoy paying not much more on average on fuel than their mid-size counterparts, making them wiser choices for those that need lots of space but want to save on fuel.

In fact, they even slightly beat the fuel costs of medium-sized SUVs for normal driving.

• The large SUV class includes the Volvo XC90, Land Rover Discovery Sport and BMW X5
• The large estate class is home to family cars including the Audi A4 Avant, Ford Mondeo Estate and BMW 5-series Touring
• Large people carriers includes the Renault Scenic, Volkswagen Sharan and Ford Galaxy.

Cutting down on fuel costs while driving

The way you drive can have a huge effect on how often you'll need to fill up your tank. Here are some tips on improving your fuel economy:

• Drive smoothly and avoid harsh braking - ease off the gas and use the highest gear available where possible
• Check tyre pressure - make sure it's correct as stated in your car's handbook
• Clean out your car - the more items in your car, the harder the engine has to work to support the weight
• Don't warm up your engine - instead drive your car gently after turning it on
• Maintain your car regularly - a freshly-serviced car uses fuel more efficiently
• Use a sat nav - take the shortest route, check for traffic updates and avoid heavy traffic
• If you drive a plug-in hybrid, charge the battery before you set off to use less fuel.

Want to calculate your own fuel costs? Use our annual fuel cost calculator.

Which? fuel research

We calculate 'normal driving' by using a combined MPG (miles per gallon) figure which takes into account that normal drivers spend their time in a mixture of urban areas, out of town and on motorways.

For comparison purposes, fuel costs are calculated using the proportional average annual mileage, which is 9,700 miles.* We took an average of the costs for petrol and diesel cars from all Which? reviewed cars for each of the comparisons.

Fuel costs have been calculated using average petrol and diesel costs for the UK in March 2019, according to PetrolPrices.com.

We have taken the average MPG figures across all fuel types in each class for the comparison, including petrol, diesel, petrol-hybrid and diesel-hybrid cars. We've combined compact and mid-size people carriers together into one class for data comparison purposes.

All sales data is taken from the SMMT.

All models named are examples of cars in the classes.