Engine Why does my gas mileage suck?

Why does my gas mileage suck?

I recently noticed that my car (03 Corolla S) has steadily declined in gas mileage. I used to get around 175km per quarter tank on regular driving. Now I am down to about 120km per quarter tank. I do a lot of driving (being a realtor) and as such I am concerned with what is going on.

I perform oil changes on 4800km everytime. They always ask me if I 'really' want to change my oil as it looks clean (which is good I guess).

Modifications to date:

1.75 inch lowering springs
K&N air filter
18 inch rim upgrade

That is it to date...

Any ideas?

have you ever cleaned your throttle body. check your pcv system. how is your driving habits???

injectors might need cleaning or just an additive u know, PVC valve (which I don't think but check it anyways), city driving will do that to your car for sure and of course if u gun it every corner lol

What is you 18" tires' diameter? If it's more than the stock 25", you're actually travelling more kilometers than indicated, and also suffering from taller gearing at city speeds.

yep, it's the tires. I have 18's on fatty tires. I seen a big decrease.

idk why but mine sucks major ass too... 14mpg...

i would guess it's k&n airfilter. they use oil in thoes filters that sometimes clog up the maf sensor. i have never used an aftermarket airfilter. becuase i feel the orignal one's are good enough.

The width on my tires is 7.5. It's wierd that you would think the K&N would cause a problem. When I put one in my wife's civic her mpg went up slightly. I hear the injectors in the morning, so maybe it is my injectors...

What is the make, model and size of your tires? Are they inflated to 30 PSI? A K&N filter helps, as long as it's not over-oiled. What you're hearing is probably your VSV valve ticking, which is normal...
How do you count a "1/4" tank? I get 800 Kms (75% city/25%Hwy) on 55 liters of 91 octane=41 MPG(Imp) or 34.24 MPG(US) with my 2003 Corolla 5spd with CAI, smooth bored/coolant bypass TB, matched+smoothed intake+exhaust manifold and ports, header, high-flow exhaust, UDP, Amsoil synthetic in engine, tranny and P/S, Bosch Platinum 4's, ground upgrade... oh and I add Lucas Fuel Treatment to all my tankfulls. http://www.lucasoil.com/products/di...atid=2&loc=show
I got a case of 12 quarts for cheap and I also use it in my Yamaha WR426...

for thoes who don't know it yet, lucas really works. i do recommend lucas.

By the way, here's an easy and precise metric conversion; Kms/litersX2.825=MPG(Imperial)
For USA gallons, it's: Kms/litersX2.354.

what kind of rims are they light weight? because i used to have 18 inch motegi rims that weigh about 27 pounds on my car and they made my gas mileage suck but now im running with 17 inch motegi trak lights that weigh about 14 pounds no more bad gas mileage

one common way to lose gas milleage- breaks, if needed to be adjusted or replaced mess w. ur mpg alot. also was your wheels properly balanced with wheel weights?

Its the diameter of the wheel not being calibrated to the odometer he's traviling father than the odometer says. If he travels 100 miles the odometer will only read 75 miles there by he is seeing 75 when he actually traveled 100. go past a towns you are going this fast stand and see how far off youre speed odometer is off i guarentee thats off too.
100 miles 5 gallons 20 mpgs
75 miles 5 gallons 15 mpgs