My Frontier 4x4 is also a 5-speed manual. I get 19-20 mpg 89 octane, but this is not my travel vehicle. A 4-cyl Nissan Frontier would have given my more economy fuel-wise, but I like that v6 when I carry full loads up hills, etc.
For traveling, I drive a 2006 Subaru Outback wagon 4-cyl non turbo 5 speed manual. That yields 26-28 mpg 87 octane. Once you drive over 60mph (freeway speeds), the mpg drops to the 26 range. At 50-55 mph I get 28mpg. In town, I get 26mpg.
The Nissan is used as a carry vehicle -- a truck. The Subaru is our family car.
miles driven: Nissan 42,000 over 7 years; Subaru 22,000 over one year