Hello, I'm Chris.I will do my best to answer your question fast and accurate using the info you have provided. Thanks for visiting Just Answer.
Are you wanting a truck or SUV?
Do you want a large vehicle or mid size or small one?
What kind of fuel mileage are you expecting?
Give me a percentage the vehicle will stay on the road and off road?
Manual or auto transmission?
New or used and if used how old at max?
I suggest a:
Now just so you know if you jump up in size to a larger SUV like the ones mentioned above your going to see less fuel mileage. All are going to struggle to hit 22mpg, especially if the vehicle is outfitted with items like larger tires or a lift kit and extra weight from gear. Many are advertised in the 19-24 mpg range but the higher end is advertised under optimum driving conditions.
Now if you decide to get a truck and put a topper on it for the dogs then that increases your options and hauling capabilities and still keeps the dogs out of the elements. Like the Ford F150 or Chevy 1500 for example.
To get the best fuel mileage you need a axle ratio with the lowest number, this will hurt you on low end power like when off road but you can use low range if needed. Just coming out and saying you need this ratio cant happen because it all depends on which vehicle you choose. Each has different gears in the transmission. So if I said you need a 3.05 in the expedition and you did the same to the Toyota then the Toyota would have to low of a gear and be weak and the expedition would be set up for highway gearing. Most imports and smaller trucks and suvs use a higher numbered gear ratio and larger trucks use lower numbered ones.
For example on my truck. My F350 has a V10 with a 4.10 if it were a diesel it would come with a 3.73. If it were commercial and used as an ambulance it would have a 4.30. You can also get a 3.55 or 4.80 in this same model. As you can see there are alot of ratios just for one vehicle and the transmission gearing and engine power can be a factor on which is needed.