Engine light came on then went off and is using a lot of gas

Check tune up items, Spark plugs & plug wires, Filters= fuel, air, ect. Use fuel injection cleaner in fuel to clean up injectors, Check for vacuum leaks, See if a code has been stored on computer(can have that done at auto-parts stores.

agree, also it wouldn't hurt to check for vac leaks. but getting that code is going to be very important.