Buick.
All D1s, P38 RRs, and DIIs are Buick based Rover V8s
2003-2005 RANGE Rovers are BMW M62s
2005-2009 LR3s are Jag/Ford 4.4s
2006-2009 Range Rover and Range Rover Sports are either 4.2 SC or 4.4 Jag Ford engines
2010+ all were Jag/Ford engines either 5.0, 3.0, and TD6

 

 

X1 ............ agreed.

Originally developed from the Buick 5.25 (I think that's correct) engine and sleeved down to the 3.5 engine for the D1 and RRC and latterly increased incrementally to larger injected engines. BMW had some impact for their short ownership period but since Ford have played a major role in engine supply. These days you are buying a Ford engine in Range Rovers and Jaguars.

The Buick engine, I believe, was developed from the failed Mercury V8 marine engine.

Their are a few early RR's with VM diesel engines around but very few. The TD5 was the last diesel engine ever developed by Landrover for the D2 and Defender.

 

Started life as the Buick 215 V8 (3.5 liter) then they bumped the displacement up to 3.9 etc. Don't believe it was based on anything from Mercury Marine or at least never seen anything on that. So its possible.

 

I can't vouch for the provenance of the article in LRO AR but research by one US guy discovered the origins of the Buick back to a V8 Mercury marine engine.

 

Here's a pretty good read on the engine. You have to scroll down to the 215 small block.
The second link is for the rover.
https://en.wikipedia.org/wiki/Buick_...ck_small-block
https://en.wikipedia.org/wiki/Rover_V8_engine

 

A light aside. Many years ago I shoe horned a Crescent Cat outboard engine into a a racing motorcycle and latterly a two stroke Konig engine. Both were a great success. Unfortunately in a couple of races in the 60's there were some unnecessary fatalities which created the safety regulations everyone see's today. I shoe horned many different engines into my sidecar and solo motorcycles over that decade, it was a time for experimenting.