I just purchased a 98 Civic HX in very clean condition. It is completely stock. I'm wanting to know what basic modifications I can do to increase the fuel economy even more. I'm not really interested in getting more performance (if I can and get better mileage I'm okay with that, for sure) but really interested in getting the maximum gas mileage that I can!

Thanks

 

Install a freer-flowing air filter, make sure your tires are properly inflated, bring all the maintenance up to date, remove power steering (if the DX has P/S - I'm not certain), have your fuel injectors cleaned and reconditioned, double-check spark plug gap, et cetera.

 

Drop a K&N air filter into the box? Stay out of high rpms even if it means a "not so fast" take off.

 

give it a proper tune

 

try shaving some weight. get some ultra light weight wheels. Losing unsprung weight should make a difference. Maybe you could create a warm air intake like those crazy insight owners make.

 

Put on thinner tires and add a well designed front lower lip.
Consider a moderate set of lowering springs to lower the amount of air that travels under the car as well

You could go as far as adding an AFC to lean out the fuel map a bit, sealing the hood spaces with silicone and blocking off the upper grill w/ a sheet of abs plastic from behind (but thats a little extreme)

 

Are you getting OEM spec MPG.