Why does my car run out of gas extremely fast?

I own a 02 Honda accord and the last time I took it for an oil change, I flushed the radiator, transmission and new air filter. Lately my gas runs out extremely fast to the point where the other day I had half a tank and within maybe 2 or less hours, I was on E with the light on. The car is not leaking gas. Also my car accelerates slow, especially up hill.

Need more info. What is your actual MPG?

A standard honda has about a 12 gallon tank. Since you are going through gas so very fast, i have to wonder if the fuel system is not dumping it into the oil pan, past the fuel pressure regulator. Check the oil level and actually smell the dipstick at the end with oil. If you smell gas, then we're on the right track.

No idea. What kind of mileage are you getting? What size is the tank? Need more information.

Get synthetic oil