Losing gas mileage

i installed a cold air intake, borla muffler, and 17" rims. Since then i realize that i have been losing alot of gas mileage. i used to average about 36 mpg now its about 27 mpg. . i just had it serviced, and had the fuel system cleaned. i would like to know is it normal for these kind of upgrades? also the car is driven mostly on the highway.

mostly my guess its those big 17" wheels..Back in the day when i was into 17"s id notice a drop in gas mileage...

I useually buy 16" at the tops most times stick with 15"s..

If your not throwing any codes and keep the maintanence up that would be my guess...

Then again could be the aftermarket parts but ive never had that happen to me mine always stayed same gas mileage wise or better

what gas mileage should i get with a 97 HX?

i'm only gettin about 30 is that low? and it is all stock too

97 hx i tought those HX"s was made to get good gas mileage if im not mistaking and most likely yes 30 is low for it...

I dunno my g/f's 97 auto lx only cuts around 32-33 with a bad 02 sensor all stock car..

30 may be about right then again im not really sure...

I'm also having a gas mileage problem. My check engine light came on for the cat converter and my gas mileage immediately went from 37 to 34. After having the cat replaced the mileage went down AGAIN. Now I get around 32. It's driving me crazy. (I have a stock 98 lx manual)

check if your engine oil has sludge. i hear from mechanics that cars with CAIs are more prone to building sludge.

add some fuel injector cleaner. the injectors may have some build up.
maybe even some new spark plugs and wires.

ive also read/heard that some of the engine oil additives that reduce friction works. theres a company that guarantees their product [not the as-seen-on-tv one. a reputable company lol]. i dont have it on hand. but i can get back to u if u want.

maybe switch to full synthetic.. its a lil more pricey than a regular oil change. usually $10 to $15 more. but i did feel a difference IMO.

maybe ure flooring it too much lol.. i know i tend to. lol

theres no real one thing that'll increase your mileage.. but for sure, keeping the car in shape will help prevent losing gas mileage. technically, the CAI and the muffler is supposed to increase mileage.. since ure get a better air/fuel mixture and less exhaust restrain.

I noticed that once I got my intake on my car, I like to apply my foot more just for the sound... maybe your doing the same thing?