harvey93

hey i got a 97 gt couple weeks ago. cel is on cause it has no cats so i searched up what it would do to the computer. been hearing that it really messes up your fuel economy. anyone want to confirm this and if so how much of a difference. it has cai and flowmasters

teej281

anytime a cel is on your gas mileage probably will not be where it should be. and it will probably cost you anywhere from 2-5mpg i'd say.

harvey93

thats alrite lol not like i bought the car for the milage anyways... probably explains why i got 19ish L per 100 k ( 13ish mpg) ripping it around town

tbirdscwd

Anytime you remove a restriction in the flow of air through the engine, efficiency is increased...... Just because a check engine light is on, does not mean mpg is affected at all.

You should have the codes checked to see what they are caused by. The codes may not have anything to do with the cats.

uberstang1

+1 Generally the only time gas mileage is affected is if the code related to a lean condition or rich condition, pretty much anything which would cause the computer to compensate for a poor air/fuel mixture.

MU71L4710N

incorrect. a CEL on for no cats has zero effect on gas mileage in any way shape or form. its just there to tell you your emissions system isnt working right.

however, there can be a SLIGHT side effect to gas mileage from free-er flowing exhaust, but its nothing substantial just changing the midpipe.

kugzgt

dont worry about, get yourself some mil's and youll be set

stangalator

this, you can make them for next to nothing and splice them in.
http://www.paladinmicro.com/PalMFrame00.htm?wks=mil

TRUEBLUE3934

Either get a pair of MIL Eliminators or a tuner to address the MIL.
Let us know afterwards if it actually had any impact on the fuel mileage. I believe it will have no impact on mileage.

MU71L4710N

i'm telling you, it has ZERO impact on fuel economy. hell i drove around for 2 years with my CEL on because i flat out didnt care if the light was on or off because my mil elims stopped working after 6 months. its ONLY there to tell you your cats arent working. the rear 02 sensors have ZERO impact on the way your car runs PERIOD. the front 02's do though, but are not related to a CEL for cats not working.