I don't know what a PHEV is, never heard of that term. I'm talking about the hybrids that have had complaints about their MPG, that plug in to recharge their batteries. Some people don't seem to realise they need to be plugged in. At a wall outlet. Or if they can find a charging station, there.
I don't know if you mean plug-in hybrids have nothing to do with efficiency in the tests? Because plugging them in generally does have everything to do with efficiency. The main point of plug-ins is because it is meant to cost less to run them, which of course depends on how much you pay for electricity. (as well as of course the whole problem with fossil fuels etc)
Offhand I can't remember every make-model and which ones are full electric, etc, but generally that is what makes them desirable, is that you get a huge amount of mileage for a tiny amount of money paid.
In any case, it was just an on-topic comment about related complaints about MPG. The point being sometimes people don't check what the quoted figures mean, or don't check how often and when they need to plug the vehicle in to recharge.
PHEV is a Plug-in Hybrid Vehicle. Only about half a dozen on the market, and very few owners seem to have quibbles with them. Their MPGe figures are very much circumstantial upon individual circumstance, the main one being how much you plug it in.
However a PHEV will still have a max MPG figure for being used as a HV (hybrid vehicle) only. This is where the fun starts.
My Prius Plug In averages about 80/85MPG real world, but I'm only doing about 15% of my mileage in EV (Electric Vehicle) mode, most is done in HV. This will return about 66MPG in the winter to 80MPG in the summer with no plugging in. This is well short of the 134.5MPGe figures given, but I expected this as I'm a high mileage user and I've bought the car for other long term reasons.
Take the Outlander PHEV though, 148MPGe claimed, but in with HV only use averages about 35mpg! MPGe figures (which is what you're referring to) will all depending upon the % of EV driving you do vs HV. You'll either fall short, or potentially smash it, I know one Prius PHEV driver that is getting over 200MPG average!
Don't get traditional hybrids and PHEVs confused though, they're vehicle different vehicles that'll give very different performance figures.
Traditional hybrids tend to fall short in the winter as the design of the Atkinson engine, as its fuel economy is very much based upon its thermal efficiency at max operating temperature. Run it in the winter with heater on full in the car and in stop start traffic and it'll only be sitting at about 50C rather than 90C.
Even Hybrids will vary from manufacture and upon if they're series or parallel hybrid systems (thats an interesting read in itself).
I do agree though, far to many never seem to do even basic research when spending thousands of pounds on a car, which is stupid if you ask me, but each to their own.