A Prius might be able to get you the economy, but there is no way it will do the performance. Nor is it a superb motorway car because the petrol engine is a bit weedy for the size/weight of the car.
You know a current Prius will do 0-60 in 10.4s? Better than the 1.6 TDI eco cars. It’ll cruise quite happily on the motorway as you’d expect something with a 1.8 petrol (plus a load of electric assistance when you want it) to. Even the weedier Yaris Hybrid is sub-12 so in spec.
Granted, for long motorway runs and no traffic or short hops, the diesels will be more economical.
I thought it would be easy to beat.
What are you looking to “beat”?
More economical on a 70mph cruise? Tricky, as you always need a certain amount of energy to push through the air, and there’s only small gains to be made now.
Lower CO2? Most of the eco-diesels have been pushing to get below 100g/km, but that’s more from optimising for EU tests that emphasise urban driving.
Quicker for the same economy? Maybe a little, for the same reasons.
Sadly, no-one has yet made a 200mpg, 0-60 in 6 seconds, 150mph car that they’ll sell for the price of a diesel golf.
If you’ve got somewhere to charge it and normally do less than 50 miles per journey, then an Ampera would do nicely. Implication of long motorway trips kind of rules that out though.