Ours was 2 wheel drive Glos Guy, so you might struggle to match it. For those of a technical bent, the B48 engine has two tricks to maximise gas flow through the engine. First, it doesn’t use a throttle body but has a third camshaft to give variable lift to the inlet valves instead. Secondly it uses a twin scroll turbo allowing even pulses by pairing the cylinders in separate paths through the exhaust manifold. I don’t know if any other engine does these things. I know Volvo’s don’t.
None of which means a thing to me Wigwam ? All I know is that it’s whisper quiet when driven normally, sounds great when given some beans and yet returns very respectable fuel economy, which is a bonus.
My wife has reminded me that we got 600 miles out of a tank last summer thanks to the combination of a larger fuel tank and good mpg. Only ever had that from a diesel before.