07 Yaris Hatch - Bad MPG?

[07liftback]

So having owned the Yaris for about 8 years, my best tank was from a 400+ mile trip from San Francisco to Los Angeles where I achieved 45mpg. I made another post about it, believing it might have been from claying my car but I also drafted behind large trucks for 80% of the trip. This was right after I changed the Air Fuel (Precat oxygen) Sensor, plugs, pcv, all fluids, and pumped tires to 45psi. I even made a front grill block for the trip that I forgot to mention in that post.

However, I used to get 34 mpg with 80% highway driving and 20% city, 12 miles each way per day. I then started getting 28-30mpg driving about 30% freeway and 70% city, 6 miles each way everyday. In both scenarios, I rarely get stuck in traffic and I'm shifting before 2k rpm.

I implement every hypermiling technique I can think of other than engine off coasting. I usually downshift as I come to a stop without touching the gas pedal which should cut off the fuel for that duration of time while at the same time slowing me down before applying the brakes. I drive slowly up hills and gain speed going down hills to conserve fuel. It seems that no matter what I try, I can't even get close to other members numbers in the 40-60mpg range.

I also have a 96 miata that I drive like a bat out of hell. It gets mid to high 20s with zero hypermiling techniques on the same exact commute. The only mod it has are the lowered suspension where it's about 1-2" off the ground. I also fill it up with Costco gasoline.

At this rate, I'm really disappointed with mpg of my Yaris since everyone on this forum seems to be getting 40+ mpg and it doesn't sound like they're taking on extreme hypermiling techniques which I used to get to 45mpg. Really don't know what else could be wrong other than the Costco gasoline I've been using.