Gaya's Mahabodhi: Tumse Milne Ko Dil Karta hai, Tumhi Ho Jispe Dil Marta hai - Ashwani Kumar

I believe 4-5 WDP4B locos were given the HOG feature (40001 being one of them). But IR never took the HOG feature seriously in diesel locos. For electrified sections, using HOG locos will help save diesel. But on un-electrified sections, it doesn't really make a difference as both the loco and EOG use diesel only. The HOG for diesel locos wasn't a failure, rather it was just not useful in the way they were doing it.
Also, an E-loco can have a HOG feature without losing it's traction power. Since the power is drawn from the OHE, it can just draw the additional power from OHE while maintaining it's regular hauling power.
For...
more...

a diesel loco however, the power supply is limited ( it is only as much as the diesel generator can generate). So, if a HOG feature is to be given, then the tractive power will be reduced, making it difficult to haul heavy loads.
For example, if 500 HP is required for powering all the lights, fans A/C etc in a rake, and if HOG is to be used, then an e-loco and a d-loco will differ in the following way (using a WAP7 and a WDP4B as examples).
1) WAP7 - The WAP7 can get the additional HP directly from the OHE, by just having a higher capacity transformer. So, while a non-HOG WAP7 has 6350 HP for powering the traction motors and the other equipment in the loco, a HOG loco will still have the same 6350HP available for the loco and the additional 500 HP will be directly derived from the OHE.
2) WDP4B - The only source of power on a d-loco is the diesel generator, which has a limited capacity. So, in a 4500HP WDP4B, 500 HP will be used up for the HOG, leaving only 4000HP for the loco, reducing it's hauling capacity.