Does Gas Mileage Increase After 1st Oil Change?

[ChilliwackGuy]

I bought a new 2010 Yaris 5 Dr Hatch (Auto) on June 5, 10 - in Chilliwack BC, Canada. So far - I have been getting about 6.1 - 7.2 L per 100 KMs mileage. I usually drive it about 200-250KMs a day during my commute (90% Highway / 10% City) - and I fill it to the 2nd click - using 87 rated Cost-Co gas in Abbotsford BC.

My salesperson said that I can expect my mileage to get better after the 1st oil change - which is scheduled for 8000KM. He said that because it's a new car - with a new engine - there will be a lot of engine / gear debris - and once that's all removed - my gas mileage will increase.

Is that true? Does the gas mileage increase after the 1st oil change? (I sure hope it does as my current Yaris mileage isn't that much better than what I was getting using my wife's 09 Rav 4 - 4WD Limited (Auto).)

Thanks!