gas mileage cut in half!

o2bfishn · Post by **o2bfishn** » Thu Sep 20, 2007 5:55 am

holy hole in the gas tank batman! did i hit a rock that went through my tank? nope just changed spark plugs and oil and now my gas mileage went from 26mpg to 13mpg. here is what i did, any thoughts are appreciated

i made the switch to amsoil (please do not turn this thread into why amsoil sucks or i should have stayed with regular oil). at the same time i replaced the plugs with ngk iridium ix plugs, wix air filter and amsoil oil filter. i also used amsoil engine flush before i switched over. i gapped the plugs to about .36 (or .036 cant remember) all plugs were the same.

i did this one day after filling my tank (filled the tank last thursday 9/13 and did the oil change that friday 9/14). i usually go about a week in between fillups so on my way to work last night i was not surprised that the low gas light came on. when i stopped to fill up i checked the trip odometer and freaked out when it said i had only gone 139.3 miles. it is usually around 280 or so. i put 10.5 gallons in. thats about 13.25 mpg

i really dont think there is anything wrong with the car, i mean i havent lost any power, i dont hear anything funny, it doesnt feel like it is missing or not firing on all cylinders. could there be something i am missing? im gonna go another week or tank full to see if it corrects itself but if it stays at 13mpg (these are highway mpg) im gonna replace the plugs and go back to good ole champions

yankeesking · Post by **yankeesking** » Thu Sep 20, 2007 6:35 am

i'm pretty sure it is Oxygen Sensor. Mine was failed with Oxygen Sensor and my gas tank empty in 2 days or less.

jT · Post by jT » Thu Sep 20, 2007 6:43 am

maybe you changed your driving habits without realizing. gunning the engine and petal to the metal frequently will drain the gas tank.

i also typically get around 280 miles per tank depending on my driving habits.. cant say its been as low as 139 though...

Adionik · Post by **Adionik** » Thu Sep 20, 2007 10:44 am

I put $10 in two days ago. I got 3.7 gallons of 87 octane. I drove around 92 miles according to my odometer and i let the gas gauge go down pretty damn low with the light on like usual. So by my math i'm getting around 24 mpg...at the most.

i feel ya though. i put gas almost every 3 days. these cars freaking suck ass with gas.

2003silverneonsxt · Post by **2003silverneonsxt** » Thu Sep 20, 2007 11:47 am

my car as no problems getting 30+ mpg city driving.. and 40ish or more highway...

i had a problem where i was getting poo for mpg and realized i had a leak in my supply line under the hood,, fixed that and the gas mileage went back to normal...

i run Q syn. oil ...
mobile 1 filter i think is whats in it..
champion plugs..
and imash it sometimes when the honda or w/e wants to play on the

circuit:

Post by **occasional demons** » Thu Sep 20, 2007 12:28 pm

Check your plug wires possibly got damaged pulling them to do the plugs. The only two items that were changed that would affect mileage were air filter and plugs. maybe there is an issue with the air filter also. But I would check the plug wires first don't recall the allowable resistance in ohms tho, anyone?

aperson · Post by **aperson** » Thu Sep 20, 2007 11:51 pm

Sounds like either the engine flush fouled your O2 Sensor to me.

jrumann59 · Post by **jrumann59** » Fri Sep 21, 2007 12:38 am

start up the car and see if your exhaust smells like gas, could be thermostat or coolant temperature sensor.

o2bfishn · Post by **o2bfishn** » Fri Sep 21, 2007 12:55 am

ok i may have figured out where some of my gas mileage went. when i did the oil change i ran the engine flush which requires you to run your car at idle for 15-20 minutes and i did make a couple of short trips to the store on saturday, but that still shouldnt account for 50% of the gas mileage, but i guess it could. so far as of today it seems to be normal again, i will keep track this week and hopefully everything will be back to normal. sorry i spazed out about this, it just hit me that i only had half my gas mileage after an oil/spark plug change

thanks for the suggestions and concern! i love 2gn.org!

aperson · Post by **aperson** » Fri Sep 21, 2007 1:03 am

If it comes back you could try to reset your ECU, that should reset fuel trims and everything.

o2bfishn · Post by **o2bfishn** » Fri Sep 21, 2007 4:00 am

will do, thanks

Arro · Post by **Arro** » Fri Sep 21, 2007 11:24 am

yankeesking wrote:i'm pretty sure it is Oxygen Sensor. Mine was failed with Oxygen Sensor and my gas tank empty in 2 days or less.

Pay attention to this statement. If it doesn't resolve, try this.

o2bfishn · Post by **o2bfishn** » Fri Sep 21, 2007 6:29 pm

the o2 sensor is down on the exhaust right? not that one that plug into the air intake before the filter box?

Arro · Post by **Arro** » Fri Sep 21, 2007 6:39 pm

yes, the exhaust. To remove it you gotta buy a special O2 sensor socket, because it has a slotted side to slip the wire into. Most auto parts stores and Sears should have them.