Car has been using a lot more gas lately
 

I drive a nissan versa 2010 and recently ive noticed my car seems to be using double the fuel. I have been checking under my car for leaks and nothing also when i went for my oil change asked them to check the gas tank and they said it was fine, any other ideas of whats going on ?

Check tyre pressures and check for binding brakes. The easiest way to check the brakes is to go for a run for a couple of miles. Try to avoid touching the brakes, especially when making your final stop. Then check the wheel centres (be careful as you can get a burn if one is binding). They should all be cold.

After that, make sure all the maintenance is up to date, though I think problems with spark plugs and such would have the check engine light on.

Just a thought but I had really poor mileage on a jeep and couldn't figure out why, changed plugs, ran some injector cleaner, air filter changed no luck. So I lived with it for a while, about 2months ago on a really cold morning I noticed that the vehicle wouldn't make temp, and as I drove faster the temp actually went down slightly. Default setting on a broken thermostat is "open" keeping coolant moving through the radiator. Changed the thermostat and voila mileage went up.

Particularly if you do lots of short journeys or live in an area of particularly low temperatures. Jazz has a blue light which stays on until the engine heats up (red if it goes over temperature). I don't even put the heating on until my blue light goes out.

One thing to check is the pcv valve. Its really easy to check and it will cause increased fuel consumption if its bad. Its a little device on the top left hand side of the engine with a hose attached to it. Unclamp the hose and unscrew the valve. Shake the valve and listen for it to make a rattling sound. If it doesn't rattle, install a new one.