yes, there will be a difference. it stands to reason that with an increased engine size, so will there be an increase in the amount of fuel needed to power it. so be prepared to spend more at the petrol pupms
I'm no expert but could it not also be the case that a smaller engine in a same-sized body would have to work harder to move the same weight of metal. The 1.8 could do the same work with less effort and therfore be more economical in the long run.