Well there you go, I've just gone and bought a tin [petrol treatment]
My motor is 5 years and 5 months old, having covered 39,700 miles. So I thought a good clean of the fuelling system components could do no harm.
So I then decided to do the maths, to look at the financial aspect of the exercise.
On brimmed fuel tank checking I'm returning 32.84 mpg per annum on last years mileage of 5,676 ending 22nd October 09. Since that date, I'm doing mostly urban driving [no holiday touring belting down motorways as yet] and I've returned 31.39 mpg over the 1,259 miles since covered.
Now a petrol using reviewer on the website indicated he was getting an improved mpg of 4.61%. So leaving aside any increase in performance or smoothness I may get. And just applying the same 4.61% improvement to my mpg [1.51 mpg] it would result in a saving of £46 in fuel costs per annum. So at £23.00 delivered, its a self financing improvement in engine efficiency, and the remaining £23 saving might just buy the oil for my next service
EDIT: Just looked on Halfords website and the 5lt of oil I bought for £22 last October is £29 now.That's a 31.82% increase, bloody oil speculators