Frontier low gas mileage

as the subject.....

2002 Frontier 2.4 XE manual transmission
the truck is pretty new, only 30K,
runs just fine, powerful, and no codes.

but---only 20 mpg???
city, highway doesn't matter, only 20mpg....

and even when my dad drive it, it's the same,
so I don't think it's because of the driving skill.

Then....what might be the problem?
spark plugs, air filter's clean....what else?

Count yourself lucky to get 20 mpg. I traded my 93 hardbody 4x4 with 175,000 miles, that got 23 mpg, for a nice 2001 frontier 4x4 with 58,000 miles. The truck is great and looks sharp. I balme myself becasue I assumed the new truck would get relatively good gas efficiency. After all the vehicle is a Nissan and much newer. Boy was I wrong, my Frontier only runs at 15 mpg. Like you it does not depend on how I drive or if someone else drives. I love the truck and the Nissan reputation but I am dissapointed with the lack of gas efficiency.

Count yourself lucky to get 20 mpg. I traded my 93 hardbody 4x4 with 175,000 miles, that got 23 mpg, for a nice 2001 frontier 4x4 with 58,000 miles. The truck is great and looks sharp. I balme myself becasue I assumed the new truck would get relatively good gas efficiency. After all the vehicle is a Nissan and much newer. Boy was I wrong, my Frontier only runs at 15 mpg. Like you it does not depend on how I drive or if someone else drives. I love the truck and the Nissan reputation but I am dissapointed with the lack of gas efficiency.

Same with my 04. Manufacturer says something like 21 highway, 18 city, I'm lucky if I break 16 mpg, city or highway, babying it or lead footing it. On top of that, it has virtually no power. I hear the SC version is much worse. I feel your pain. I've thought about putting a K&N,, flowmaster, chip, all that stuff, but I don't think anything will help all that much. Just stuck with it. I think the Titan gets better gas mileage than the Frontier.....

I have a 03 with a 3.3 or 3.5 not sure, but it gets a steady 22+ mpg. Most of my driving is highway except during trapping season but I still get a steady 22+. I will admit in the snow in 4wd it is a little lower but not much, maybe 19. It also pulls my boat easily.

if you have 30k on the vech you can try doing a major service and a injector cleaning. that may help