It start with a worrying 'fact' which was wrong.....
Well I fail to see how it is wrong.
All Pacers and Sprinters are older than the Turbos. The 139 runs on battery and only uses diesel in the event of a flat battery. This leaves 168, 170, 172, 175, 180 and 185s as the diesel units newer than the 166s and as I mentioned 172s were a newer unit we discount them.
I've already mentioned how many of the routes 170s were originally intended for were long distance. This has changed due to 222s coming in to operation and some being cascaded to ScotRail, as well as the Central reorganisation which has put them on shorter routes than originally e.g. Birmingham to Stansted Airport instead of Liverpool to Stansted Airport. One of the most significant factors of the use of the former CT 170s now is that
EMT» run Liverpool-Norwich but all the CT 170s went to either
LM▸ or
XC▸ , meaning LM have too many to put them all on longer distance services. 170s have a 100mph top speed and slower acceleration than the Sprinters, which doesn't exactly make them a good choice for stopping services.
168s are used on Birmingham-London, which does probably make the 168s one of the less debatable options but then the 168s are the oldest after the 166s.
175s were built for the FNW Regional Express services such as Llandudno-Manchester, Manchester Airport to Windermere and Birmingham to Holyhead. 185s were built for routes like Manchester Airport to Newcastle/Middlesbrough/Cleethorphes and Liverpool to Scarbrough and since finished up being used to replace Voyagers on Manchester Airport to Glasgow/Edinburgh.
180s I think we can call intercity. It was rumoured that the original 180 design was drawn up for FNW's open access Blackpool-London service but after Virgin got competition protection FNW's parent company
FGW▸ were still interested in using 180s.