horrible gas mileage?

[JDM_SPEC_SI-R]

anyone want to explain the upstream o2 sensor? is it the one on the air intake?

 

[Billy.]

upstream o2 sensor (on an obd2 ecu) reads the exhaust gases to determine the level of unburnt fuel and oxygen left. if this sensor fails, or is inaccurate, you will get bad gas mileage as you will be running an incorrect air/fuel ratio.

there is no intake o2 sensor. only temp, pressure sensors

to mugenej8power; you need to calculate the exact amount of gas consumed on a trip of known mileage to calculate your mpg. saying "i got 350miles to a tank" is not accurate enough. use NOFX's method to determine your mpg

its as simple as topping off the tank and reseting the trip odometer. drive around for a couple days til youve consumed a considerate amount of gas. top off the tank again and look at the pump's lcd screen to see exactly how much gas it took to fill back up, and look at your odometer to see how many miles you accumulated. divide the mileage by the gallons used

 

[NOFX]

To show how innacurate it can be when you just state how many miles you're near empty, here's an example.

Once I filled up close to empty I drove 355.7 miles.

My tank is 11.9 gallons. So that'd be 29mpg.

Even if I said that I estimated I'd used 11 gallons, that'd be 32 mpg.

My car does not get 32 miles per gallon.




So now I look at the receipt from the gas station.

It looks like I actually put in 10.222 gallons.

So I actually got almost 35 mpg.

Notice how big of a difference you can get between estimating how much gas you used and actually knowing.

 

[X-aCuTiOnA]

The MPG concept only works if you (1) Completely fill up each time and (2) reset your tripometer each time. Forgeting either will throw off you calculations.

Like NOFX said, you need to be exact. Rounded numbers dont say anything.

 

[Billy.]

you only have to reset the odometer once when you top off the first time, dont have to remember to do anything else. the 2nd time you top off look at the odometer and the pump reading. that's it. it isnt calculus drivin quantum physics . its 2 steps

 

[Milano_SI]

thanks for the replies guys.ill b sure to try NOFXs ideas once wen i have to fill up next time

 

[gearbox]

even if you do what nofx says. there is still a small amount of error because the pump may click off a bit early or late compared to last time, yes even at the exact same pump. ive actually had some pump click off way before the tank was filled. so thats why its important to repeat this several times and see how your mileage compares over time.

 

[HiPWR Racing]

you know.. i also think it could depend on what kind of gas you use or where you buy it from.

like casey's gas where i live just isnt right. but when i fill up somewhere else its a different story..

so i dont really know just throwin that idea out there ;p

 

[anfrey]

it can be done easily without the trip meter... just note your odometer reading.

www.mymilemarker.com may help you out

 

[Billy.]

even if you do what nofx says. there is still a small amount of error because the pump may click off a bit early or late compared to last time, yes even at the exact same pump. ive actually had some pump click off way before the tank was filled. so thats why its important to repeat this several times and see how your mileage compares over time.

it should be within 1/2 gallon of error

 

[gearbox]

sometimes the gas gauge didnt even make it to full tho. i had to try another pump.

 

[anfrey]

tire pressure does wonders for fuel economy

 

[EK|B]

tire pressure does wonders for fuel economy

Yes, but sadly most drivers are ignorant of this fact.

 

[DarkCreep]

Theres STILL plenty of room for error because like I said, you couldve pumped 10 gallons of gas in there, and had 1 gallon in there to begin with.

Would a better way of measuring your mileage be,
Top off the tank
wait till the needle hits EXACTLY in the middle.
Then measure that? That would be 5.95 gallons remaining in the tank, that is unless there is more then 11.9 gallons in the tank for reserve or something.



I just switched over to synthetic on Thursday. Im going to fill up today and see if my mileage went up. It lowered and I was like "WTF happened?" THen I forgot I was 500 miles overdue.

 

[NOFX]

Theres STILL plenty of room for error because like I said, you couldve pumped 10 gallons of gas in there, and had 1 gallon in there to begin with.

Would a better way of measuring your mileage be,
Top off the tank
wait till the needle hits EXACTLY in the middle.
Then measure that? That would be 5.95 gallons remaining in the tank, that is unless there is more then 11.9 gallons in the tank for reserve or something.



I just switched over to synthetic on Thursday. Im going to fill up today and see if my mileage went up. It lowered and I was like "WTF happened?" THen I forgot I was 500 miles overdue.

No. The fuel gauge is not that accurate.

You are just not understanding how to measure mpg.

Okay, it DOES NOT MATTER HOW MUCH IS IN YOUR TANK.

It matters how much you USED on that trip that was of _____ miles.

Don't use the fuel gauge to measure how much gas you have, but more to just tell you when to fill it up. It's not reliable, especially not that reliable.

Say you pump 10 gallons in. As long as THE LAST TIME YOU FILLED UP YOU RESET THE ODOMETER, it doesn't matter.

I'll go over it again.

FIRST TRIP TO THE GAS STATION

1 - Fill up your tank.
2 - Reset the odometer.
3 - Be on your way.

You can't yet measure how much your gas mileage is because you don't have reliable information.

SECOND TRIP TO THE GAS STATION

1 - Fill up your tank.
2 - Print receipt.
3 - Write down odometer reading on receipt.
4 - (odometer reading) divided by (gallons of gas just put int he tank) = (gas mileage)
5 - Reset odometer.
6 - Be on your way.

After that just do the same thing outlined in "second trip to the gas station".

This will fairly reliably give you your gas mileage reading. If you continue to record it, you will find out the average gas mileage of your vehicle and find out what your limit might be.

Use this site:
www/gassavers.org

Here's even the example you mentioned.

"you couldve pumped 10 gallons of gas in there, and had 1 gallon in there to begin with"

Okay, So say my tank has an even 11 gallon capacity.

I drive 300 miles since I last filled my tank to the top.

I fill the tank up and find that I had used (and just put in) 10 even gallons of gas.

So 300 miles (distance driven) divided by 10 gallons (gas used) equals my gas mileage, which is 30 mpg.

The amount left in the tank doesn't matter. I could have a 40 gallon tank, drive 300 miles, put in 10 gallons to replace what I'd used and I STILL got 30 mpg.

 

[NOFX]

I've tried to make a visual example here for DarkCreep.

The last time you filled up your gas tank, you filled it up all the way.

Here is your gas tank now.

You have driven 225 miles since the last time you filled up your gas tank.

1 - How many gallons do you put into the tank in order to fill the tank back up?

2 - How many gallons did you use on your 225 mile trip?

3 - What is your gas mileage in miles per gallon?

 

[SiGSR]

LoL. What is so hard in figuring out your MPG? I hope this doesn't require to be stickied.

 

[J_Uhrig87]

you don't do the math based on your fuel tank size, you do it by what the pump says you filled up, and it only works if you fill it up all the way the time before. when you feel up all the way, and you set your trip meter you have to do the math how many miles you went on your trip meter devided by how many gallons the pump says. it'll be a lot lower if you go by tank size cause it's impossible to run the tank dry, well, not unless you want a seized motor. so when you fill up next time use your trip, devide that amount by how much you filled up.
also you might need a fuel system flushed

 

[anfrey]

LoL. What is so hard in figuring out your MPG? I hope this doesn't require to be stickied.

lol right!! i mean, the name itself tells us the formula... MPG... miles per gallon... miles/gallon... lol

 

[Billy.]

this is starting to get ridiculous