LC 90 Series - Explain "generations" please?

[Dieseldragon]

My 2001 90 is a D4D.

If you can find a D4D, they are significantly more powerful in standard form and a bit more economical. I think the d4d engine was only available in 2001 and 2002 models.

 

[TALAMAN]

Many thanks Dieseldragon! I am not sure why at this stage but I feel that I would prefer to get a D4D for a number of reasons, even though they cost a lot more here. Still avidly researching and looking.
Geoff