There's quite a difference in MPG between traditional port injected and direct injected petrol cars.

When the 3l 3 Series swapped from the N52 (port injected) to the direct injected N53 it got an extra 10 real world mpg.

Obviously direct injection comes with it's own issues of injectors carboning up and needing higher pressure (less reliable) fuel pumps, etc.. .

That's true. However the figures the poster of this thread mentions are very very similar to those I was getting 25 years ago on a 2 litre automatic petrol estate car, so I maintain that progress hasn't happened to any great degree - at least as far as that particular engine is concerned.

Power output - now that's a different thing entirely, modern engines are far more efficient at creating horses and torque from the same amount of fuel.

The engines are more efficient but the weight of the cars have gone up 40% to 50% so the outcome is a similar mpg.

FWIW my XC90 T8 has averaged 52mpg over 32k miles. Typically mid 30s if I’m fully laden and can’t charge.

My S4 Avant (2017 /354ps) did 30 overall with 34 on a run. My 2.0 petrol Golf R estate (310ps) once did 40mpg on a run and averaged 34.

Back to the thread, I would buy a petrol hybrid if driving in London. As above 52mpg demonstrates for a Volvo. My overall mpg would be great if I was doing 25m a day on electric and only using diesel out of urban areas, but it's still at 70+, so despite the weight of lugging batteries around, hybrids are definitely a good compromise...

• My old 2020 BMW M340i 4 wheel drive 369 BHP = 48 mpg on my 40 mile trip to work
• My 2019 V60 T5 R Design Pro 250 BHP = 35.7 mpg on the same trip.

The Volvo averages about 25 mpg most of the time.

Cylinder-on-demand is definitely a good thing for fuel consumption. I had a Seat Leon loan car when our car was in for body repairs for a couple of weeks and when I wasn't thrashing it across country, it would happily pootle about on 2 cylinders.

I fully agree with this statement, my old RS6 Performance would do nearly 40mpg on a long run thanks to cylinder deactivation technology, not bad for a 2 ton, 4 wheel drive 600bhp estate.
My current XC60 Recharge PE will do similar but requires a fully charged battery, if its empty (or I have it on hold for the long trip), its low to mid 30's.