I Don't Think My Yaris Has DFCO

[BailOut]

I see 45mph speeds listed. If thats the case, its no wonder you get in the 40+ range per gallon.

As you mentioned that is the average speed, taking into account city and highway driving (30-35 MPH in the city, 55-60 MPH highway). The reality of my daily commute is a twisting, winding, 2 lane, 30-50 MPH climb over a 4,500ft mountain (8,900ft summit), dropping 2,500ft on the back side, then the opposite on the way home. That is very far from optimal mileage conditions, especially in the colder months.

If you want to get better MPG on the highway the #1 thing you can do to help yourself is to slow down. Every MPH you drive over 55 takes away 1% of your fuel efficiency, and every MPH above 65 takes away as much as 5% due to the physics of aerodynamics. A common example used is that it takes an average of 20% more fuel to drive 70 than it does to drive 55. Get in the right-hand lane and stick to 55 MPH and watch your MPG shoot up.

Pumping up your tires to at least the max sidewall rating not only improves handling on wet and dry pavement but also increases MPG by decreasing rolling resistance, and increases the life of your tires by producing a much more even tread wear pattern. As an example I run my RE92's at 60 PSI for most of the year, dropping them to 44 PSI (which is the max sidewall) in snowy conditions.

Btw, the site linked in my sig, CleanMPG.com, isn't mine. I'm just a member and contributor. You can read much more about increasing your MPG there, and start logging your own fuel usage if you like.