Speed will rule the day in your quest for 25 mpg. Last May I drove from Houston to Phoenix via I-10, many miles and hours through TX with 80 mph speed limit, set cruise for 85 mph, was showing between 24 ~ 26 mpg with 35d. Have driven 55 mph highway other times for comparison and can see over 30 mpg. 25 mpg with 3.0 at 70? Maybe. 75 to 80? Maybe not.