On my previous 2.0 TDI, i used mainly Shell or Esso regular diesel. Every 1.5-2000 miles I would give it a tank of Shell Vpower Nitro Plus Diesel to give things a little clean and piece of mind haha. Oh and btw, on Vpower the engine seemed to regen less.
From my experience, Shell Vpower gave better mpg, perhaps also more power on a dyno, but day to day driving, I cannot feel the extra power. However I found the mpg increase really didn't offset the higher price. I got the car @ 2248 miles and had it till 10k miles, so engine was clean to start with. Once I put in 10 liters worth of supermarket diesel to see what gives. Engine was grumpy and a bit unwilling. Like us just waking up and not wanting to go for a jog. Even a friend commented, 'whats with your engine, got up from the wrong side of bed?' and he doesn't know what fuel I put, but he's been in my car frequently to notice a change.
However another experience with my former flatmate who had a Renault Clio 1.5 88PS DCi benefited more from Vpower. It's because for most of it's life it has used Supermarket fuel. Journeys were the same Mon - Fri, same time, same 'conditions' etc. I pressured her to do this test, as I was curious, she finally gave in. This is what happened.
As her journeys were as consistent as consistent can be, a full tank of supermarket diesel, she would need to refuel every x number of days. I cannot remember if it was 11 or 13, but anyway, that was the base experience. Despite cursing and swearing at the 'extra' must have been 10p or more at the pumps, she went through with it, to keep me from pestering her. Anyway...on the first tankful of Vpower, the car went 1 more day same conditions, and on the 2nd tank it went almost a 2nd day more. Essentially it gave about 60 more miles a tank. Now she uses Vpower exclusively. Engine quieter too, when asked about more power, she said, cannot feel.
Perhaps it's the Vpower's powerful cleaning agents getting rid of the supermaket fuel gunk/junk after a couple of tanks restoring it to it's 'near new' former glory. I compare it to descaling a kettle
. I do wonder if she 'downgrades' to regular Shell/BP/Esso diesel if it would still give it the same range.
I would say start with a full tank or 2 of Vpower Diesel (to clean whatever supermarket fuel deposits/gunk might have been used/leftover prior), then just go back to regular Shell/Esso/BP diesel, and then base your preferences from there after trying both the premium and regular.
I know this is for a petrol (in which premium fuel might work more wonders)
Shell Regular 95
Shell Vpower (as similar a journey can be, albeit I was distracted hence had to go around the roundabout twice, hence slower speed)
The 1st leg on Vpower