Mercedes-AMG E63 vs BMW Alpina B5

What's the difference?

Feels like lately all the Mercedes-AMG buzz has been at the smaller end of the scale.

Most recently, the screaming GLA 45 S has arrived in Australia, pumping out more kilowatts and newton-metres than any compact SUV has a right to.

But here, we're doubling the cylinder count to eight, arranging them in a vee, and lighting the wick on AMG's powerhouse mid-size sedan, the recently upgraded E 63 S.

While the ferocious twin-turbo V8 and the rest of this beast's powertrain are unchanged, the car has been brought up to speed with some aero-focused styling tweaks, Merc's latest 'Widescreen' digital cockpit, as well as the MBUX multimedia system, and a tricky new multi-function sports steering wheel.

The BMW Alpina B5 Bi-Turbo is not actually a BMW. Not according to the German Federal Motor Transport Authority, at least.

Nope, the modifications applied by tuning house Alpina to the 5 Series are deemed so significant that if you open the bonnet and look inside the engine bay, you'll see that the BMW VIN has been struck through twice and an Alpina vehicle number stamped underneath it. 

The B5 is not the first model to be recognised in this way, either; the German government has recognised Alpina as a seperate car manufacturer since 1983.

The B5 has other ‘B' siblings, too. There's the B3 S Bi-Turbo, which is based on the BMW 3 Series, the B4 S Bi-Turbo (the BMW 4 Series) and the B7 Bi-Turbo (I don't need to tell you what this is based on, right?) which I've reviewed, too.

So just what has Alpina done to this unsuspecting BMW 5 Series? Is it really worth the extra money? How does the B5 compare to an M5? Could it actually be superior? And did they really take the speed limiter off to let it warp-speed to beyond 300km/h?