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Old 08-31-2017, 01:49 AM
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Originally Posted by RockinWs6
If you are only getting 6 miles per gal I'd say your car would smell like fuel coming out the tail pipes and your cats would be melted into cat heaven. How are you actually calculating your mileage?
No smells and I fill up drive fill up again and calculate miles per gallon
Old 08-31-2017, 07:47 AM
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Originally Posted by chevylsx
Worse tank ever I've got an 1/8 tank left and only 81 miles driven!!!!
That after replacing O2 sensors?
Old 08-31-2017, 09:11 AM
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Sorry but I don't believe this.
Old 08-31-2017, 10:19 AM
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Replace oxygen sensors.


If problem persists inspect fuel pump. I had a pressure line leak in tank and it would cause the fuel pump to stress itself and best I can figure evaporate fuel as it over heated from all the extra work
Old 08-31-2017, 11:08 AM
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Originally Posted by chevylsx
Worse tank ever I've got an 1/8 tank left and only 81 miles driven!!!!
At 1/8 tank you would have used 14.7 gallons. That's 5.5mpg. A carbed 454ci Suburban would get similar MPG trailering maximum capacity, up a hill, in 4-wheel drive.

Not sure how it could be that bad without tripping a MIL and/or having other driveability issues, unless you spend 95% of your time at WOT. Are you sure you don't have a fuel leak somewhere? Otherwise, MAF and/or front O2s need some attention - but the exhaust should smell so rich that you almost can't stand anywhere near it with the engine running.
Old 08-31-2017, 11:19 AM
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I don't get much better gas mileage. I had a thread on here when I first bought my car. Mileage was horrific, got about 150 miles per tank. Didn't matter how I drove the car, normally or feather footed. Then one day I got over 200 while hammering it fairly good on a long drive. Makes zero sense. Haven't found an issue. I never drive it so it doesn't bother me.

To those saying BS - nah dude. This **** happens. My car has 30K BTW and is 100% stock except for pulley and lid - with a PAPER filter.
Old 08-31-2017, 11:44 AM
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Originally Posted by AnotherWs6
I don't get much better gas mileage. I had a thread on here when I first bought my car. Mileage was horrific, got about 150 miles per tank.
Assuming you didn't run the tank dry and filled up with no more than ~15 gallons of fuel, you were getting about twice the MPG of the OP's latest tank. At 5.5mpg, his results are not normal and his car most certainly has an issue of some sort.

FWIW, I had no issues getting ~12mpg out of my '00 WS6 with an A4, 3.23s and a 3500 stall TC in city driving. That was not being easy on the throttle either. My stock LS1s have usually gotten 14-16mpg with all city driving, all A4 cars.
Old 08-31-2017, 12:52 PM
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Mine got 20 to 22 with just headers when i first bought it. Mostly hwy.
Old 08-31-2017, 01:13 PM
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he has plugged cats.
Old 08-31-2017, 01:32 PM
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Originally Posted by farmington
he has plugged cats.
That doesn't seem very likely based on the details given earlier:

Originally Posted by chevylsx
...I started using it as my daily driver and man it drove like a new car the engine runs strong with no tapping or knocking or any problems whatsoever the engine truly feels 100%...
If the cats are clogged bad enough to cause this sort of MPG loss even with ultra-conservative driving, I don't see how the engine could run/feel 100% even at part throttle. But it would be a simple test; the OP could do a WOT run and if the engine pulls strong all the way to redline without any issues, and the cats aren't glowing red after the fact, then his problem likely lies elsewhere.
Old 08-31-2017, 03:25 PM
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The cats would be toasted by now, they can't handle that much raw fuel for very long. That's why I just don't believe too much of what this dood posted. Plus if its stock it should go into cat protection mode............
Old 08-31-2017, 03:52 PM
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Originally Posted by RockinWs6
The cats would be toasted by now, they can't handle that much raw fuel for very long. That's why I just don't believe too much of what this dood posted. Plus if its stock it should go into cat protection mode............
I still wonder if he doesn't have a fuel leak somewhere, that's the best explanation for a ~5mpg result from super easy driving without any SES light and absolutely zero driveability issues of any kind from idle to WOT.
Old 08-31-2017, 06:31 PM
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If I suspected a fuel leak, I would let the car sit somewhere without wind, and run the fuel system to stay on for a while. You would be able to smell the fuel if the leak is significant. I do this test before running an engine after I put it or the fuel system into a car. Make sure to smell everything first before you do the test to ensure the fuel isn't already there (which would still "find" a leak).
Old 09-01-2017, 12:42 AM
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Originally Posted by RockinWs6
The cats would be toasted by now, they can't handle that much raw fuel for very long. That's why I just don't believe too much of what this dood posted. Plus if its stock it should go into cat protection mode............
Cat protection mode dumps even moar fuel I thought.

But plugged cars cost me 70+ hp on a dyno a couple years back now. You can definitely feel it
Old 09-01-2017, 12:43 AM
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Originally Posted by RPM WS6
I still wonder if he doesn't have a fuel leak somewhere, that's the best explanation for a ~5mpg result from super easy driving without any SES light and absolutely zero driveability issues of any kind from idle to WOT.
Agreed. But you'd think just being parked overnight you'd smell it. Car in a parking lot has a gas leak you can tell from 30 feet away
Old 09-01-2017, 01:29 AM
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Originally Posted by Darth_V8r
Agreed. But you'd think just being parked overnight you'd smell it. Car in a parking lot has a gas leak you can tell from 30 feet away
Yeah, and it would need to be leaking a pretty significant amount to have such a huge impact on MPG. I'd expect it to be easy to smell and pretty easy to see the evidence if you park in the same spot all the time. But there's the possibility that it's only leaking under pressure, which was touched on in this post:

Originally Posted by kingtal0n
If I suspected a fuel leak, I would let the car sit somewhere without wind, and run the fuel system to stay on for a while.
Maybe a small line leak under pressure, perhaps only during times of heavier fuel flow and maybe not even visible at idle. If none of the scanner data looks out of sorts, it might be worth inspecting the system for any signs of leaks.
Old 09-01-2017, 11:29 AM
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You all need a holiday/vacation... You are missing the most obvious thing.

The OP should set up a security camera on the car 24/7 and look out for bums siphoning gas out of the tank.
Old 09-01-2017, 11:35 AM
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Originally Posted by Darth_V8r
Cat protection mode dumps even more fuel I thought.

But plugged cars cost me 70+ hp on a dyno a couple years back now. You can definitely feel it
It does, its an enrichment table.

Originally Posted by wssix99
You all need a holiday/vacation... You are missing the most obvious thing.

The OP should set up a security camera on the car 24/7 and look out for bums siphoning gas out of the tank.
Let them have their fun.
Old 09-01-2017, 11:36 AM
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My point is the CHECK ENGINE light should be on.
Old 09-01-2017, 11:47 AM
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Originally Posted by wssix99
You all need a holiday/vacation... You are missing the most obvious thing.

The OP should set up a security camera on the car 24/7 and look out for bums siphoning gas out of the tank.
Excellent work, I think you have just found the most likely solution.


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