Tessie was bought new in 2006 for my Wife's primary vehicle. When new, it was quite easy to have mixed-tanks in the 30+MPG range and mid-30's on highway trips. The slick Cd of 0.27 definitely helps.
Fuel fill records were never kept until within the last year or so, but I'm driving it more these days. Unfortunately, it has developed a long-term decrease in FE. Many factors could be at work, including heat deformation of the factory undertray, and the need for a tune-up. ~90,000 miles at current writing.
Tires are inflated to 50 psi front /45 rear.
Four, Low-RR Michelins replaced 2 BFGs up front and worn Mich's in the rear at about 80K miles. Synthetic transmission fluid and engine oil used. Personal driving style: manual, sequential shifting.
Basically get it back to factory efficiency... make an attempt to get the undertray under control, and a tune-up is in order soon.