Is250 MPG

[Linas.P]

I agree in general, but there are caveats - Octane booster actually reduces the temp not raises it. Again, probably it won't hurt, but the carbon issues is specific to intake valves, cylinders themselves and exhaust vales burns carbon deposits when at the operating temp for prolonged periods of time anyway. So I guess the only part where cleaners could help is the injectors. 

[Fishboy]

I managed 46mpg driving from Staffordshire to Gloucestershire on a quiet Saturday evening, however once off the motorway and tackling the hills of Stroud it soon dropped. Not bad though for a V6 with over 130k on the bores.

[H3XME]

If you're getting really bad mpg, you should probably think of using V-power and floor it frequently. Carbon build ups are common on these engine. Good fuel will reduce it building up, but you still need to stretch its legs every now and again. Full throttle everywhere 😄 Works for me.