Valve adjustment and economy

[pj67coll]

I've owned my car for ten months. I did my first ever valve adjustment in mind November and have noticed a definite increase in fuel consumption since then. I was consistently getting about 31,5 mpg before that and since then it's been just over 29mpg.

All the valves were tight as possible when I did them but it's quite possible I might have done a less than perfect job of adjustment. My question is could that account for the increase in fuel consumption? My driving routine and filling stations have not changed at all during this time.

- Peter.