Rapid decrease in MPG

[Davdraco1]

As the title states, idk what's causing my MPG to drop so much. I used to get about 350 to a tank and I drove it on the highway long enough to use a tank and the gas light came on and I had only travelled 240 miles. I've done highway drives with it before and I got 410 miles before I filled up. Any thoughts?

[richardodn]

Fuel leak.

[Davdraco1]

I'm replacing the injector seats in the next day or so. I replaced the injector o rings bc there was fuel residue by 2 of the injectors. That was months ago and it ran with no issues. Are there any other locations that are common to leak fuel?

[Tamarillo]

That's a big loss for feul leak so surely you would find it with engine on car stationary and wait to see if anything drops or smells?

If not maybe it's burning it and is badly out of tune, and there my knowledge ends as these days there are so many factors that can cause such problems I'd just check for leaks and if none found put it in for tune test report. I'm assuming the on board diagnostics will identify ang problem?

[B5A4coastie]

Do you have an AFR gauge?

[Davdraco1]

I don't have an AFR guage. I do have a full 3 in cat back and a gutted cat. The primary O2 sensor is still in place. I've had that set up for 10 months tho with no issues. I'll get it scanned, my friend has vdcs

[Davdraco1]

I just read that there are two different o rings needed for the injectors? The uppers and lowers are different?

[viceprp]

You have rings at the rail and in the seat ends. I'm not familiar with stock application.

You will see a drop in mpg during these months. On my NA vehicle, I saw a 30% drop due to longer warm ups, and cold dense air. Same goes for the B6 but that only will see ~ 15% drop.

[Davdraco1]

I'm literally getting half the mpg I used to. And it happened overnight. There's got to be a fuel leak somewhere.

[adam044]

I'm literally getting half the mpg I used to. And it happened overnight. There's got to be a fuel leak somewhere.

would be obvious as your fuel gauge would drop overnight without the car being driven.

[Davdraco1]

What if it's just a slight leak and it only leaks when the pump is creating pressure in the system?

[viceprp]

What if it's just a slight leak and it only leaks when the pump is creating pressure in the system?

Turn your car on and look where your fuel rail feed connection is. Look where any fuel line connects. If it's a leak, that is where it'll happen, especially with the weather we have been having.

[adam044]

Do you smell any fuel when you get in your car? Even a small leak will be easy to smell. I know because I have a small leak when I fill up, so now I don't fill up anymore. My car would wreak of gas every time I would completely fill up and my mechanic noticed it was leaking from the top a little when I brought in it to get axles. I had filled it up right before I dropped it off so that's why he noticed it.

[Davdraco1]

I guess a little smell when the heat is on. I know there is raw fuel by the injectors so I'm replacing the seats soon. I already replaced the o rings. I checked where the fuel pump is and there are no leaks there. The fuel lines conected to the fuel rail are fine as well.