I'm trying to hunt down the cause for why my gas mileage is below par. I really should be seeing better mileage consider my car is stock and I don't have a real heavy right foot and the car is an M6. Although, I do think my gas gauge is misleading me how much gas is really left
Are all these parts related to gas mileage? Am I missing any

• Plugs
• Wires
• O2 Sensors
• Fuel Filter
• Air Filter
• PCV Valve

I've been slacking and have only done fuel filter and plugs so far. The passanger side O2 is impossible to get out on the manifolds, what combonation will get it out? I have a Moroso CAI, what is the best way to recharge the filter?

Thanks

 

new 02's will probably make the biggest difference pending nothing else is to messed up....i usually clean my filter with some dishsoap in a bucket of water, put it in, agitate it, repeat a couple times....then i leave it in the sun to dry and then put some filter oil on it, and its clean and ready to go

 

Good List.

I don't know if it will help, but you may want to clean your MAF sensor with electrical cleaner (spray can), I have never done it myself but have heard of it being done to get the most accurate readings during dyno tunes.

Tire pressure is an easy one.

If you have cats make sure that they are not ecxessively restricting the flow. I had a friend with a early 90s Yota pickup. His milage went to crap for a 4 cylinder and it ended up burnung the carpet in the extend cab above the cat.

 

Bad exhaust leak could make you rich. Don't know about an intake leak.

02s are expensive.....

As far as the guage mine goes almost another full 1/4 mark past "F". When it shows 3/4 I have maybe 1/2 left. If it gets down to 1/4 I have to start looking quick. Stays at full forever then drops to empty within a few miles.

 

i would say check you 0s i had a problem like that with my 6 a wile back

 

I'm 99% it is the O2 sensors because the car has 120k on it with the original senors. I tried changing the sensors before but I just couldn't get the passanger side out with the stock manifolds (passanger side). Anyone that has changed them on the manifolds; how did you get them out?

 

I changed mine out when the headers went on @ 120k. Nightmare to get them out. Worse than the exhaust bolts I think. I used lots of wd40 and a really big crescent (adjustable, not the brand) wrench with a hammer. I used the hammer to break it all loose, even after that it was a fight.

 

Run a bottle of fuel system/injector cleaner.

 

Yes, these gauges are very innacurate. The gas sloshes around all over when turning and what not. Mine acts the exact same way. Although when you reach 1/4 tank, i would say you arent in danger, but it is interesting to note that when i fill up from half a tank it is maybe 3 bucks cheaper than letting it go down under 1/4 tank.

 

when added my euro gauges I fixed the problem buy filling up my tank as much as I could and a also I bought a gallon in a gas can, Drove home and added the gas in the gas can so that I would literally top it on and when I installed my euros I popped the gas needle off and moved it to the F and not a half tank before F .. Now I know if I'm on E I can make it to a gas station.. Its very easy to correct this problem..

 

I had trouble changing my passenger side O2 as well. Tried multiple times, with a variety of tools, and continued to fail.

I called around to all the smaller exhaust shops (non-national shops), and was quoted $25. I jumped on it.

The guy said he had to heat it with a torch to get it to even move, and then it would move a little, and he'd have to heat it again. It took him 1.5 hours to remove it. I gave him $35.



The gauges are not inaccurate.
It's the shape of the tank that causes this, because the tank is much wider at the top than at the bottom, as the gas level gets lower it gets lower faster.

BTW;
To find your mileage, start with a full tank.
Take a mileage reading, or set your trip meter.
Drive any amount and fill it back up.
Subtract your gallon useage from the original amount (15.5 gallons is full). This would be the gas used.
Divide your mileage traveled by the gallons used.

I just add this because there seem to be confusion on how to track and find your mileage. It has nothing to do with your gas gauge.

 

If you subtract what you put in your tank from the total the tank can hold, that would be the amount of gas unused or left over. Instead, you want to divide the mileage you drove by the amount of gallons you added to your tank to top it off.

 

All the suggestions above, but make sure your calculating correct, i wouldn't go by the gauge, either the trip or the reg. odometer. I fill at about 180 (trip) and usually put in somwhere around 11 gallons. 180/11= 16.36mpg. Sorry if Im talking down to you, but some of the explanations looked a little confusing.

 

i wish you were able to see this with the older cars like my 94

 

If I am not mistaken, GM has always had issues with it's fuel gauges. It takes many miles to move it off FULL and as it drops, it drops faster and faster. I believe all GM's are like this.
I can drive about 100 miles before I see it budge. Then it starts slowly dropping but seems to gain momentum on it's way down.
Not much can really do about it. I know in my Dodge, when I have 1/2 tank, I have 1/2 tank.