Does this really make a difference to performance? Like can you actually tell? Does it increase or decrease mpg! Is it worth the extra few pennies!

Generally the posh stuff should give you an extra few mpg per tank and a little extra in terms of performance. Ive beren filling up with BP Ultimate for the past couple of months and cant say ive noticed anything performance wise but have noticed the extra few mpg! As to weather its worth it, depends on your driving, commute, no. of miles you do etc.....!

I mainly switched as the posh stuff helps clean and look after your engine!