BMW may not be the first manufacturer you think of when petrol-electric cars crop up in the conversation, but it does have two such vehicles on sale in the UK. The first is the ActiveHybrid 5 which we've already discussed, and the other is the smaller ActiveHybrid 3 shown here.There are several similarities between the two. Both have a twin-turbo three-litre petrol engine and an electric motor with a combined maximum power output of 340bhp. Both have eight-speed automatic transmission, as an increasing number of BMWs do these days. And, just like the 5, the 3 is not expected to be at all popular in the UK.Why not? Because if this is the kind of 3-Series you want, the obvious choice is the 330d turbo diesel, which is more economical, nearly as quick and nearly £7000 cheaper. Thing is, though, Americans are still not happy about buying diesels, so when it comes to selling a powerful but not too thirsty car over there the ActiveHybrid makes more sense. And since the US is where BMW can make most money from hybrids, we have to make do with this one and rue the fact that there is not, for the moment, a smaller-engined diesel-electric to consider.The battery pack eats into some of the luggage space, which comes down from the standard 3 saloon's 480 litres to 390 litres, but you can increase that again by folding down the rear seats, which you can't in the 5.The pack is also quite heavy, and it has a significant effect on the handling, to the point where you might almost believe you were driving the world's first mid-engined production 3-Series.It's still good to drive (I have yet to come across a current-model 3-Series that isn't) but the extra weight dulls its reactions slightly, making this a performance car in the sense that it can accelerate hard in a straight line rather than make easy work of a challenging sequence of corners.In M Sport form as tested here, the ActiveHybrid runs on 18" wheels fitted with low-profile 225/45 run-flat tyres. No better reason exists for saving money and buying the cheaper SE version instead. Those tyres had a catastrophic effect on the ActiveHybrid 5 I drove, and the same applies here - far, far too much road noise and a ride whose jarring firmness could not be tempered even by switching to the Comfort setting on the £750 optional adaptive suspension.That apart, I quite enjoyed the ActiveHybrid 3, and it's nice to think that in town it can travel for a couple of miles on electric power alone if there's enough charge in the battery.But I'd still have the 330d every time - or, for vastly better fuel economy and a reasonable proportion of the driving experience, the 320d EfficientDynamics, which is so good that just thinking about it has already made me forget about the ActiveHybrid 3 before I've finished writing this review. Engine 2979cc, 6 cylinders plus electric motor Power 340bhp Transmission 8-speed automatic Fuel/CO2 47.9mpg / 139g/km Acceleration 0-62mph: 5.3 seconds Top speed 155mph Price £43,225 Details correct at publication date