We have a 2012 Versa Hatchback, 1.8 SL. It was rated for 34 mpg hwy, and most of our miles are highway miles. It began with a low mpg, around 28, and steadily increased for the first few months to about 30 - 32 mpg. We got 33 mpg a couple of times with very careful driving and a higher octane fuel. Then it began to decrease. It was at 29 mpg late last fall. The local dealer couldn't determine a problem. The dealer where we purchased it did a more thorough evaluation, but with no codes being stored and no emissions testing equipment, they couldn't identify a problem. It has declined to 26 mpg, and there is a strong odor of unburned fuel when it is running. Still, no codes have been stored and Nissan representatives have said there is nothing they can do except refer me to fueleconomy.gov to learn [how to drive more efficiently.] I had a mid-size car in the 80s that got 36.6 mpg. Why is this such an impossibility? A tiny car purchased specifically for fuel economy, after doing our homework, that can't even reach 30 mpg?! (btw, our data was submitted to fueleconomy.gov last year)
The next time I "do homework", I will remember to search as I did to find this forum with "poor fuel economy" instead of "fuel economy". This is an older thread, but the issue appears to be the same.