2003 Protege Losing Gas Mileage


Mazda Protege LX
Hello. I am new here so hello and much respect to everyone. What brings me here is that I am having trouble with the amount of gas my 03 Protege is using. When I got it a year ago it was getting 400 miles/15+ gallons. Now I am getting 275 to the same 15 plus. I changed the fuel pump and pressure regulator though haven't got around to the injectors, air filter, spark plugs, or O2 sensor. Oil changes are on par and all in all, for its age, it runs well. I check constantly and there are no leaks and all hoses are connected and everything on the replacement pump is attached correctly. I do notice couple things. One is that there is/has been a strong scent of gas coming from the vehicle but I can't tell from where. I sniff like a dog all around the car and constantly check everything and for the life of me can't figure out where the scent comes from or why its making it. Also in the last couple of weeks my radiator/coolant system has developed a leak. I checked all the connecting hoses and nothing is leaking from them but the fan constantly runs. I've had that problem before and don't think this is a major contributing factor to fuel economy loss though it may be making a difference.

So if anyone has had similar experiences, I appreciate your feedback. I'm by no means an experienced mechanic but I do have some know how. Again thank all in advance
2014 Mazda3 S GT auto, 2008 MX5 6-speed
How many miles are on the odometer?

Do you know when the spark plugs and air filter were last changed? If not, have them inspected and changed, if necessary. Worn plugs and a clogged, dirty air filter can cause a loss of fuel mileage.

You may need a fan temperature switch if the fan is running constantly. Loss of coolant without a visible leak could be from a leaking head gasket. Have the coolant checked for combustion gasses.

While the car is running, check for fuel leaks under the gas tank and engine bay. Also check your gas cap's gasket. If the cap is not sealing adequately, that could be where the gas smell is coming from.