Which make the best tow cars: petrols, diesels or hybrids?
If you regularly tow a caravan, the chances are you do so with a diesel car.
But although diesel power has been very popular with caravanners for years, it’s not the only type of engine which makes a viable choice for towing a caravan.
With so much negative publicity about diesel emissions, more and more tow car drivers are looking at alternatives when choosing what tow car to buy next, whether it’s a modern petrol engine or a hybrid.
We’ll guide you through the pros and cons of each.
Why tow a caravan with a diesel?
In a word, torque. If you are looking for an engine to tow a caravan, you want one that generates plenty of twisting force (which is what ‘torque’ means).
As a rule, diesels produce more torque than equivalent petrol engines.
A modern turbodiesel typically puts out maximum torque at around 2000rpm, relatively low in the rev range. This means the engine will pull strongly without needing to be revved hard.
On the other hand, a petrol engine will generally have less torque but more peak power, delivered at higher revs than is typical for a diesel.
This means that to accelerate strongly, a petrol engine will need to be revved higher and harder than a diesel, and the driver may need to change gear more often.
Therefore, on your caravan holidays, it is much more relaxing to tow with a diesel than with a petrol.
In addition, diesels are generally more fuel-efficient when towing a caravan than petrol-engined cars.
We’ve recently compared the economy of two Volkswagen Tiguans, one petrol, one diesel. Both towed the same caravan over the same roads. While the diesel returned 30.3mpg, the petrol achieved just 20.8mpg.
More often than not, a diesel will have a higher legal towing limit than the equivalent petrol. That means you can legally tow a heavier caravan.
However, most big caravanning organisations like The Camping and Caravanning Club recommend towing no more than 85% of the kerbweight of the tow car, especially if you are new to towing.
As diesels are generally heavier than petrols, they can pull heavier caravans and still abide by this advice.
So why consider a petrol tow car?
Over recent years, many car makers have introduced turbocharged petrol engines which have partly closed the gap in pulling power between petrol and diesel engines.
For example, the VW Tiguan TSI which we tested in our recent petrol vs diesel comparison has 236lb ft of torque, just 15lb ft less than the diesel equivalent.
These turbocharged engines tend to deliver their pulling power at lower revs than non-turbo petrols, making them more diesel-like in the middle of the rev range, while still having plenty of top-end punch.
As a rule they’re also more economical – certainly according to the official figures – although they still don’t match the best diesels.
Petrol-powered cars are generally cheaper to buy than equivalent diesels. Using the VW Tiguan as an example again, the price difference between the two cars in otherwise identical specification is just over £500.
If you drive a lot of short journeys, petrol may be a better choice than diesel, because the particulate filters diesel cars use to clean up their exhaust gases can become clogged if the car is mostly used for brief, stop-start journeys.
Many car buyers are considering switching to petrol for environmental reasons. However, if we’re talking about new cars which meet the Euro 6 emissions standard, the difference in the permitted levels of nitrogen oxides (gases which worsen local air quality and can be harmful to human health) between petrol and diesel cars is actually quite small.
Some drivers simply prefer driving a petrol. In general they are quieter and smoother than a diesel, and keen drivers will enjoy the superior power at high revs.
Can I tow with a hybrid?
It depends on the exact make and model of the car in question.
Some hybrids are not approved for towing, and some of those which are have low legal towing limits.
For example, the Toyota Prius is restricted to towing braked or unbraked trailers weighing no more than 725kg, which rules out almost all caravans.
Larger, heavier hybrids tend to have higher legal towing limits. For example, a Lexus RX450h has a maximum towing limit of 2000kg.
Several plug-in hybrids are also capable of towing, and the best of them do so very well.
Together with colleagues from What Car? and The Camping and Caravanning Club, we economy tested this Volvo hybrid while towing a twin-axle caravan, and achieved no better than 16.1mpg.
So, what tow car will be your next purchase?
There’s no doubt that diesel is declining in popularity with most types of car buyer, and the best petrol and hybrid models make viable alternatives for tow car drivers.
However, right now, for anyone who tows a heavy caravan regularly, diesel is still the obvious choice.
The way a diesel engine delivers its pulling power makes it well suited to towing and, in reality, diesel has a significant fuel economy advantage while towing.
But with the rate at which technology is advancing, watch this space.
Catch up on the rest of our towing 101 guides:
Diesels are generally more fuel-efficient when towing a caravan than petrol-engined cars