very low mileage in city AND highway...why?
 

before i start, heres a simple list of whats on my civic 04 automatic ex that could probably affect my fuel cosumption?

aem short ram intake
catback exhaust
test pipe (catless)
*CEL is light on due to catless* (aka malfunction indicator lamp)
5w-30 motor oil (fully syn mobil 1)
factory wheels (alloys) tires are inflated properly
1 12" sub and amp in trunk (50lbs together?)



i often fill up with 76's regular 87 pump gas and probably 89 once a week. but now that in california, its gotten pretty heated (80-85 degrees), i have been getting very low gas mileage (my fathers suv litterally gets more mpg than my civic :argue: ) could it be that the intake piping is so heated to the point where i cannot hold my hand on it for 10 seconds?

my driving habits are usually spirited (never race, i only go up to 5.5k rpm at most to merge on the highway).

my best educated guess would be that i have been going on the highway often more than the last few weeks. i cruise @ approxmiately 65-70 mph with light traffic. any of you could help me out and explain to me any possiblities why im getting such low MPG all of sudden, please enlighten me :)

well you need to measure gas mileage after driving through most of the gas on the highway at a constant speed. Like drive 65mph for a few hours. Then measure it. I get very low mileage in the city, once as low as 15mpg, but highway highest was 38mpg, but usually 30-34.

If your CEL is on, the ECU is probably running in a "safe mode" - running extra rich.

try to drive within 3K in ur tach.....and always shift before it goes over 3K..

put it some engine treatment...

change ur spark plug...NGK IX is good

clean/change ur intake filter....

reset ur ECU and let the car "re-learn" the intake...

etc..