If you are positive you have no leak, then the engine is running rich. This would account for the smell of gas and poor mileage. Take it to a professional and make sure they replace the fuel filter along with finding out why it is running rich.
could be a number of reasons etc bad thermostat,clogged heater core,leaking heater core,
leaking what??
Your engine may have a leaking hose connection or a leaking gasket at the water outlet. It could also be a leaking hose.
It could be leaking from a number of places. Some could be a simple fix and others not so simple. Need more info as to where it is leaking.
If you're getting an engine warning light on your Hyundai Accent, oil could be leaking into the exhaust valve. The could also be a problem with the catalytic converter.
its the PCV valve
could be getting higher mileage and burning it, could be leaking at a gasket or seal. check and make sure the proper recommended oil viscosity is being used.
There could be many causes to a car leaking power steering fluid. There could be a hole in the reservoir, or the seals could be worn or broken.
If it's leaking transmission fluid, could be a bad pump seal. If it's leaking engine oil, could be a bad oil filter, leaking valve cover gasket, leaking intake manifold gasket, leaking oil pressure sender, leaking distributor gasket.
Passenger side floor? Could be leaking heater core
One sentence could be "Blood was leaking out of them like water from a faucet."
It could be worms.