I've done everything I can think of to get my MPG back up to what it used to be and nothing seems to work. I get around 250 miles per tank. I have:

Replaced the Knock Sensor

Replaced the Fuel Filter

Put in Mobil 1 Oil

Replaced EGR

Cleaned all Carbon buildup out of Intake

Since all of this I went from about 220 a tank to about 250, but I used to get about 300.. And the first tank after I changed my fuel filter and put in Mobil 1, I got 310.. But then it went back down again.. I'm so damn frustrated. I don't slam the gas pedal or drive like crazy and my o2 sensors are just fine. Anything I can do?? Any Ideas???

 

I'd keep going with what you were doing but also do the O2 sensors and also spark plugs anything that might be done with an intense tune-up.

 

Did you clean the air filter??? check for exhaust leaks, clogged cats?

 

Yeah, I have a K&N drop in. How do I check for exhaust leaks & clogged cats? Have to have a mechanic do it?

 

I hate when people say they do everything and then they don't do the most obvious stuff. It's the O2 sensors, how do you know they're fine? Just cause they don't set off the CEL? You replaced the EGR but did you clean all the hoses?

 

Yeah I did clean all the hoses, and they checked the o2 sensors when I took it in to replace the EGR

 

check for ghost codes.

 

What, do I need a ghost sensor?

 

i hope your kidding. a ghost code is a code that doesnt trigger the CEL to come on. EX: An o2 sensor that is about to die will still be functional so it wont trigger the light to come on but it will display the appopriate code 0707 etc/., also if the o2 dies then the CEL will come on

 

Let's tackle the obvious here:

Automatic or 5 speed?

How do you calculate your MPG?

What do you consider "a tank"?

How much do you typically put in for "a tank" full?

Has it been hot and do you run the A/C a lot?

Do you do most of your driving in the city?

Do you have larger than stock rims?

 

^^ Much needed info. Thanks Dave.

 

Sorry but you're wrong. An O2 sensor won't trigger a CEL until it dies and it does not throw ghost codes either. Only ghost code I've ever heard of or experienced is the KS code. Most if not all other sensors won't have a code, ghost or CEL, until they are completely gone.

How did they check the O2 sensors for you SOCRATES? Did they just look at them and say they are fine or check with an OBD2 scanner? Either one of those won't work. You're supposed to dip them in water of certain temperature and take a resistance reading that has to be within spec.

 

Did you replace the spark plugs?

 

I'm going to answer my own questions just to help others out in case he doesn't respond back.

Automatics tend to drink more fuel than 5 speeds. City driving kills an automatics MPG because there is a lot more slippage and energy used to operate the automatics components. In the city, an auto can typically see 10-15% less MPG. On the highway, the auto may exceed the 5 speed because the auto is geared lowered and the torque converter locks up and stops all slippage.

The only wat to accurately calculate reliable MPG is to fill your car completely up, clear the tripometer, drive, fill up again then take the driven miles divided by added gallons. This will get you to within 5% MPG.

With an 1/8 tank left, I can still easily go another 60+ miles before the light starts to come on.

This simply means are you filling it up all the way? The tank holds a crack over 18 gallons assuming you don't have a drop of fuel in it. I know that when I fill mine up, it doesn't come off of the "full" range for 60+ miles.

An A/C used around town along with hot weather equals bad MPG. An A/C can suck out about 5% MPG around town in hot weather. On the highway, the A/C really doesn't suck out too much MPG because the A/C doesn't have to run as hard to keep the car cool.

Stop and go traffice kills MPG and the same goes for hills.

By simply running my lightweight 17" rims that weigh no more than my OEM 15" combo, I see a 1.5-2.0 MPG drop. Rotational inertia is a biatch, even if no additional weight is added. The weight is further from the hub therefore the motor has to work harder to accelerate the tire/rim combo.

 

Ok Check your MPG this way:

Fill you tank ALL the way up to the top and reset the Odometer Trip 1 to 0.0
Drive to about half tank and then fill you tank ALL the way up again.
Divide the Miles on the Odometer Trip 1 by the number of gallons it took to fill the car up from half tank.
This number equals your average MPG. Then multiply that average by 18 to get how many miles per tank you're getting. (assuming your style of driving is constant)

I achieved over 30 MPG on the Highway in 5th gear at 3500 RPM or greater!

DAVE B- Awesome write-up as usual!!! I learned many things in this most recent post of yours as well as the E36 Flywheel article you posted!!!

 

Ok Check your MPG this way:

Fill your tank ALL the way up to the top and reset the Odometer Trip 1 to 0.0
Drive to about half tank and then fill you tank ALL the way up again.
Divide the Miles on the Odometer Trip 1 by the number of gallons it took to fill the car up from half tank.
This number equals your average MPG. Then multiply that average by 18 to get how many miles per tank you're getting. (assuming your style of driving is constant)

I achieved over 30 MPG on the Highway in 5th gear at 3500 RPM or greater!

DAVE B- Awesome write-up as usual!!! I learned many things in this most recent post of yours as well as the E36 Flywheel article you posted!!!

 

One of my O2 sensors triggered a cell, and it was staying around in the .1 KOHMs range instead of constantly going from .2-.8 KOHMS like they are supposed to, scanning for rich/lean situations. Because it was stuck in the .1 range it was telling the ECU that the air/ fuel mixture was too lean, and so the ECU was constantly trying to correct it by dumping more fuel. I got about 280 MPG. After I changed all of the O2 sensors and the KS, I got around 360 MPG.

 

HOLY FUKKING ****!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

Alert the newspapers and media folks, we have a new super car. Better than any hybrid or economy car. FRIGGEN AMAZEN!!!!!!

 

tire pressure

 

really sorry to bust it to ya, but i have had 4 different ghost codes. 0707 0303 0503 0304. pulled them my self, and the CEL lite didnt light up on each occasion either. But the codes were still there.

 

i run about 700kms on a tank roughly about till E comes around fill it up with 16.5 Gallons.
so i run 700*.6214 = 435 Miles on 16.5 Gallons. I get 26.36 MPG up until 16.5. So I can Probably run 460Miles on a full tanks 18.5Gallons

 

When filling up the tank twice to calculate mpg, we should go to the same gas station at the same pump for more precision right? Or is that useless?

 

Just the let you guys know, the gas quality have changed. Ever since they've added ethanol to the gas, my MPG have changed. Our cars are a bit old and the engine parts are not as fine tune as before. If I'm getting around 18 in the city and 20's in the highway, than i'm happy.

Is kind of difficulty to pin point where the problem are located. By the time we located where the problems are coming from, our cars will be 10 years old. Even with the members on the .org giving feedback and comments, we can improve the MPG, but we can't fix it. My O2222 cents.

 

Damn Dave B you just know how to school these kids... But yea basically what Dave B said answers all the questions.

I get just about 18 MPG here in NYC with almost all city driving, with the traffic here highway driving is pretty much city driving, thats with 17's and 3 or 4 WOT romps everyday.

On a recent trip upto Maine I got 27 MPG all highway, so I'm pretty happy with my auto.

 

Yeah man, Thanks for the answer post.

Mines and Auto, I get 250 to about a 17.5 gallon tank. I've been running the AC a lot, but not insane. I do a lot of city driving, but it's 7 miles of highway each way to work. Rims are stock.

I just feel like 250 is low considering I used to get a lot more and I've replaced and checked so many things.

My tires recommend a max of 35 psi, Which I usually keep about at 32. Would lower or higher help?

And How about an alighnment or balancing? I don't really get any vibration

 

Please explain your reasoning because to me 92 octane at BP is not that much different than 92 octane at Citgo.....correct me if I am missing your point.


Bruce

 

Overhaul/Clean your throttle body and lubricate the throttle butterfly. This should be done every 50T kms. To get better results, replace your fuel filter and perform oil change and tune-up (check timing, clean/replace plugs)

 

hey socrates, you said that you replaced your egr. Are you talking about the egr valve? If so I know there are two small bolts holding the valve plus a larger nut that connects to a tube. I want to clean out the egr valve but I can't figure out what size the larger nut is that connects to the tube. Do you remember what size it was? Its a pain in the a$$ to get to the valve on my 95.