I think adblue was introduced in 2017/2018I've never seen even close to 75mpg! I'm talking actual average over a tank by the way, not what the computer in the car says. Best average I've had is about 60. For town driving I think the petrol is better. Yes, the mpg drops but not as much as the diesel does on that kind of driving. To me diesel only makes sense if you're going more than average millage and it's mostly longer runs. And petrols are getting so good these days the case for diesel is even weaker. Years ago our 150hp car averaged about 30mpg but the 150hp Leon does 45 while diesel economy has not advanced by anything like that much. If at all.
I didn't know the newer cars have adblue?
You don't need to change the bottle to get rid of the silica bag, just pull it out.
The bottle did need changing - they changed the design on the later ones so the bag was sandwiched between two skins of the bottle, and impossible to remove. My 1.6 had the earlier bottle where the bag was just in a pouch and easily removed.
I was amazed at the highest fuel figure. From a full tank, it did a run from Preston to Halesowen and back, 215 miles, and I could only get 13.3 litres and £18.00 in to top it up, so it was a calculated brim to brim. The computer said 75mpg, actually worked out at 73.6, so the computer is pretty much bang on. Don't know if the adblue makes it any more or less economical to be honest.