MPG better after engine rebuild

[barker22]

After having my engine rebuilt over a week ago now, it seems like I am getting a good extra couple of mpg out of the fuel.
New spark plugs would have gone in but the old ones weren't exactly... erm.. old/worn.

It seems they also managed to roll out that shell V Power Nitro at the same time as my engine rebuild and that is all the car has run on since being rebuilt. Could it be the fuel, the rebuild, a mixture of both? Not that I am complaining just curious as to the sudden jump.

 

[Chrisgti6]

How much of a rebuild has it had?

 

[Carbonraider]

I noticed the nitro lasts longer than vpower only by a couple of miles tho. Of similar driving to and from work on the motorway.

 

[barker22]

Purely valves(all 16), gaskets, belts, all seals etc. timing was correct before and after.