My 2016 Nissan Pulsar has the Renault 1.5 diesel found in many cars of that age.including Dacia. It's torque is 250Nm @2000 rpm. That's comfortable towing a Puck but I wouldn't want less. The latest small turbo charged engines have more torque than the larger petrol your looking at. I would only consider a diesel of that age. What you need is high torque at low revs for comfortable towing. IMO

In the Dacia Duster petrol engine line up they do a 130 TCe engine which has 130bhp but pushes out 240 Nm of torque, This was the same torque as my first diesel 1.5 dci Duster in 2013 and it had plenty of power to pull my 900kg Famila 320.
The rpm is also an important factor on how hard the engine has to work to attain the max torque, the Duster turbo charged petrol 4 cylinder 130TCe engine reaches 240Nm of torque at 1600rpm where as my turbo charged 2021 1.5 diesel 4x4 Duster hits its max 260Nm of torque at 2000rpm.

Generally speaking turbocharged petrol engines give their maximum torque over a wider spread of revs than a diesel engine, so the theory goes that to achieve similar levels of performance you have to change gear more often with a diesel.

The industry recommendations for a comfortable tow is 40bhp per tonne and 80lb/ft of torque per tonne. A 1.6Sce Comfort 2WD manual has 115bhp and 115lb/ft of torque. It's kerbweight is 1179kg and its max weight is 1412kg and towing limit 1400kg. Loaded for a trip, say, it weighs 1300kg plus an 'ahem' lightweight Welsh Troll at 1000 Welsh kg's gives a train of 2.3 tonnes or so. 115bhp divided by 2.3 is 50bhp/tonne, so well above the 40 recommendation but with 115lb.ft the torque is also 50lb/ft per tonne which is well below the target 80. So it really doesn't have the grunt necessary.

It's companion 1.5 diesel Comfort 2WD manual has 114bhp and 192lb/ft of torque. It's kerbweight is 1320kg and maximum weight 1548kg with a 1500kg towing limit. loaded the same it will weigh 1.44 tonnes and with the same lightweight Welsh Troll at 1000kg the train is 2.44 tonnes. 114bhp divided by 2.44 = 47bhp/tonne so still well above the 40. 192lb/ft of torque divided by 2.44 = 79 lb/ft per tonne, almost spot on the required 80 figure.

The writer quotes these as examples and cannot accept any liability for others personal actions. Welsh Troll weights are a matter of conjecture and Welsh kg's can go up as well as down.

Not so lightweight though.

Hmmm. Change gear more often with a diesel? I don't think that's right. The rev band is almost always narrower than a petrol engine, but max torque is produced at lower revs. The old adage was that you had to rev the nuts off a small petrol engine to get it going, whilst a diesel would pull away from much lower revs. Modern engines are highly computer controlled and almost universally turbocharged to produce better power and torque, but there's still no substitute for capacity...

Our 2011 Volvo V70 has a 2 litre, 5 cylinder turbodiesel engine and it produces around 180bhp and 400Nm of torque (what caravan?). It only has a single turbo, whereas many more modern engines have twin turbos (of different sizes,) to give a wider spread of torque. My wife's 2017 Volvo V40 has the more modern 2 litre, 4 cylinder diesel engine that produces 190bhp and 400Nm of torque with excellent fuel consumption and a wider spread of power/torque due to the twin turbo installation. It's also Euro 6 compliant.This will become our tow car shortly.

Of course, to complicate matters, electric cars produce max torque from start, which is why they accelerate so fast and do, in theory, make excellent tow cars - shame about the range...

That's the point Colin, you can hang onto the revs with a petrol and still be accelerating, where with a diesel you'd need to change up to maintain that acceleration.

Petrol cars were not always so accommodating - modern petrol engines are considerably improved in both power delivery, torque and economy.

Although I'd really like a big V8...