Rauch

I always thought my fuel decided to run out pretty quickly, so after changing my oil last night, I decided to calculate my mileage.

With 20.4 miles on the counter, I filled the tank with 13.3 gallons. Might I mention below half a tank, my fuel needle is right about 40% of the damn. Damn check gauges light always let's me know.

On my drive to work this morning, I drove 57.9 miles highway, no traffic, no lights, and not going above 2,500 rpm.

As of those miles, I expended a 1/4 tank of fuel. Which, if I calculated it correctly is roughly 14 miles a gallon.. Highway. Giving me around 230 miles/tank.

No check engine lights exist, merely the random flashing brake light and abs inop light.

I feel as though my mileage should be quite a bit better than that. Mostly stock '00 SS. Just long tubes, true duals, and underdrive pulley. So either the gas gauge is wrong, or there's an issue with the o2's, possibly something a little more serious, or maybe even the tune the previous owner (stealthss) got on it.

Any ideas before I start spending some money and not get any results?

I'm think

Big Chuk

iTrader: (11)

the way to check is to top off your tank. drive at least 100 miles of normal driving. Re-top off the tank. Then check mileage. That will tell you if the gauge is broken. A common problem with these cars.
Also depends on the gears in your rear end as to what MPG you get.

LeanPocket

iTrader: (6)

this would be correct, I would drive like 30 or 60 miles hwy nonstop instead of 100

I average 20 with combined driving, check the normal areas before buying anything, cracked wires, dirty air filters, mismatched tires, under inflated tires, wrong octane, bad quality gas, plugs, old fuel filter, sea foam, gas cap loose, failing 02 sensors, loose lid, excess weight (remove ur junk) low oil, failing fuel pump.. does ur exhaust smell funky like ur running rich ?

i know thats all common sense stuff but i hope that helps, let us know what happens

Rauch

My exhaust smells sort-of rich. Not sure whether to take into consideration the lack of cats in that equation.

Out of the rest of that list, the only possibility I can see would be the fuel filter, wires, and o2 sensors.

It sounds a though there could be a misfire. Hard to tell with the overall loudness an echoing of the exhaust. I do hear what appears to be an occasional drop in rpm (nothing shows on the Gaige though), but there's a slight "puff" sound. Plugs are fairly new with the exception of the good ol number 8. That may be fixed with new wires. In a sense I'm hoping for the engine to go, just to drop in a new ls6. Gotta love warranties. But filling the tank as much as I am now is pissing me off.

Definitely changing the fuel filter once I get home as well as 4 wheel studs thanks to some unknowing people overtorquing too short of nuts as well as the wrong size..

Empatho

iTrader: (16)

Replace your 02 sensors, sometimes they go bad without triggering the check engine light.

96blackta

iTrader: (7)

I wish I got 200 miles a tank.

2001NBMZ28

Miles/tank using fuel gauge won't work. Miles/gal using pump figures doing the math does. IMO if the 02's were bad (lean, rich, insufficient switching, etc.) you'd be getting an SES.

wssix99

iTrader: (5)

I'm having the same issue and have a guess that its either my A/C bogging down the engine (I've been running it a lot/constantly lately.) or the cheap Denso O2 sensors I installed last year.

I'm going to try a non-A/C mileage run soon and will scan my O2's if that doesn't do anything dramatic.

babbage1109

iTrader: (11)

Did you ever get a tune? That will fix it

HAZ-Matt

iTrader: (8)

Yeah go by fuel pump volumes. You just need to make sure you fill it the same amount each time and it doesn't click off early.

Bad fuel econ can be caused by a whole bunch of things. Check tire pressure. Make sure the air filter isn't dirty. LT's and NB O2's don't really get along all that well. Need to scan it with something like HPTuners to get a real idea of what the fuel trims and O2s are doing.

bmartin8

If your untuned your PCM is going to keep dumping fuel to make up for the change in A/F. If your o2s and MAF dont shake hands and agree on what the A/F is your PCM is going to dump more fuel.

Rauch

Wish I had the money for it... Damn things expensive. I don't need 8 credits... Just 1. Doubt they'd deduct the other 7 from the cost.

I'm pretty sure I've got some sort of miss after it warms up. I'll hear it sporadically at different intervals each time. May as well pick up new wires and 2 widebands when I can get the funds. About to do the fuel filter in a few minutes.. Can't wait to break it open to see how/if at all dirty it is.

May as well test the coils as well while it's still daylight.

babbage1109

iTrader: (11)

Did you ever get your car tuned after you put headers on it?

Wimimc

iTrader: (2)

i've learned not to trust my gas gauge when it reads between 1/2 and 3/4 of a tank. it often moves and not accurate.

i downloaded "mr cars" app to help keep track of mileage fwiw. its pretty cool and found that i'm averaging about what i should 18-20 mpg city.

billscamaros

iTrader: (1)

Miles per gallon would be:

(ending mileage) - (beginning mileage)/gals of fuel
example: 12000 - 11000 = 1000 miles/10 gals of fuel = 100 mpg.

I track my mileage everytime that I buy gas, and I keep track of the gallons that I buy in each visit to the gas station. I use a small calendar to keep track of mileage and gas.

I average 26.5 mpg on Shell 93 octane for a 58.5 mile commute each way, mostly on four lane highway, averaging 65 mph.

'99 Z28 M6 with 220K miles.

Rauch

Just filled up and calculated mine. I'm a little over 21 mpg. I'm sure it'd be higher if it weren't for traffic and the occasional burnout under the bridge on 676 in Philly. 47 miles each way.

So I'm pretty happy now. Guess I just drive too much.

Wimimc

iTrader: (2)

if you have an A4 like me, we'll never get as good mileage as the M6 guys

HAZ-Matt

iTrader: (8)

Something simple is that you can check is to make sure all the wires are seated correctly onto the plugs and the coils. When my original wires wore out, one of them didn't click into the coil that well and it completely fell off while I was driving down the road... not saying yours fell off (will miss bad and you will hear it arc to something), but if it is a little loose there can be an small airgap the current has to jump which can make it miss.

I don't really understand why people think the fuel filter reduces mpg. It could potentially lower fuel rail pressure, which would increase fuel trims... but if the O2s are accurate it shouldn't change AFR.

My mileage is really crappy. I think part of it is that it has been about 100F each day and it is probably pulling some timing. Plus I make a bunch of short trips. Restarting the car wastes gas, and these cars get crappy mileage in the city to start with (worse since my stall too).

LS1121

iTrader: (17)

My A4 gets 25 on the highway using cruise. with air.

LS6427

iTrader: (2)

210 miles door-to-door from my house in Lauderdale to my condo in Orlando. All but 8 miles is highway on the FL Turnpike. I use half tank on the gauge + one needle width past the half mark, after filling up when the gas pump stops by itself. 70 mph. BUT....I never refilled it to see how many gallons it actually burned. I'll have to do it, I'm betting I get 26+ on the highway.......

All city driving.....sucks.....200 to a full tank if I drive mostly casually, with a few hard runs. If I have a really hard driving (fun) week, 150 miles to a full tank.

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