Good point about the wording.  There isn't that much to toot about if the increase was from say 9.4 mpg to 10 mpg.  But an excess of 10mpg as stated and what that meant to the company that ordered 500 units is something to consider.  At any rate, the company like HTI, wants to sell their product and brinkmanship is key as long as, like you say, doesn't deceive the customer.  The customer probably had a trial period with results, etc... bada bing, bada boom, I'll take 500 (to start with).