They do a V6 3.00 ltr Diesel

I think there may be some confusion over the different types of hybrid.

PHEV is a plug in hybrid, this will have a fairly large battery and could (on paper at least) do 30+ miles on electric power only.

HEV has a mich smaller battery which is designed to discharge its power and recuperate it quickly through acceleration and braking. It will run on electric power only, but typically only far a couple of miles at most.

MHEV is the very mildest hybrid variant. They won't drive on electric power alone and as such (IMO) shouldn't really be referred to as a hybrid because doing so implies, to less knowledgeable buyers/drivers at least, that it is the same as a HEV when it isn't. MHEV allows the stop/start system to work much quicker, may allow the ICE to switch off while the car is slowing down and while coasting at higher speeds (both of which will result in minor efficiency gains), and will also provide a little electrical assistance in acceleration.

My assumption from your first post mentioning a fully charged battery was that the car in question must be a PHEV because it is the only one where you charge it. But as MCB 100 points out, the diesel is only available as a MHEV. What this ultimately means for your question is that any economy "benefit" of the hybrid system might as well be ignored because of how tiny it will be. For example, If your MHEV RR Sport was averaging 25mpg on the motorway towing a caravan, the same car without MHEV would probably be averaging 24.5mpg.

Edited by badbusdriver on 17/06/2025 at 13:27