AnotherWs6

iTrader: (17)

i'm reviving this one because what the ****? I get about 10 -12 miles to the gallon with my nearly stock m6. ****, my lifted 5.3 silverado gets at least 11 no matter what. I'm not beating on it constantly either. Who are all these people pulling down 30 on the highway? IS something wrong here? I do a about a 50/50 mix of city and highway driving.

Kingc8r

iTrader: (21)

Same here with 3.73s my city driving was around 14 mpg, but highway suffered.

With 3.23s it was the opposite.

I usually got between 17-20 combined, but my foot was almost always in it at least once or twice.

M4N14C

iTrader: (3)

Many possible reasons for that, faulty/old O2 sensors, clogged up fuel & air filters, fouled plugs and a poor tune. Fix those up and you should see a significant boost in your economy.

10 is way too low for a stock LS1 even if your going WOT most of the time

AnotherWs6

iTrader: (17)

I know, thats why i revived this thread and then actually started another. Car runs great btw, has 32K miles on it and is clean as a whistle. Air cleaner is clean, i have plugs, wires and fuel filter in my garage, just need to actually put them in. I even used Chrysler's top end engine cleaner (kinda like seafoam) and couldnt get a whisp of smoke out of it. Car was 100% stock when I bought it, so I seriously doubt it was ever tuned. Just sucks for some reason. Could a bad MAF or 02's cause this? wouldnt my plugs be black if the computer was making it run way rich? They arent, I looked at a couple of them. Then again that was right after I got a bad tank of gas and the car started pinging at high RPM. The base was actually black but the porcelain and metal werent. Maybe they were black previoulsy but that high rpm detonation cleaned the **** off of the top of the plug.

01WendySue6

iTrader: (1)

Just started reading the beginning of this thread. How in the name of God are people getting 150-180 out of half a tank.... I very very very rarely get more than 100 out of half a tank. Thats with fairly easy driving. I cruise 5-10 over the speed limit and go wot maybe once or twice every few days but not daily. How the hell is my mileage that bad? Mods are just full exhaust, tune and a lid. Car was like this even when i bought it stock 1.5 years ago. Suggestions??? O2 sensors, etc i assume?

Jenson

iTrader: (32)

AnotherWS6, I wonder if someone installed a gear. To be getting that low from a good running stock car...seems the most likely explanation.

01wendy, replacing your O2 sensors at 100k miles is a good practice to get into imo. 4 wires are cheap now so why not. Thats a lot of carbon build up after 100k miles.

I easily got 25mpg hwy @ 80mph from my cam'd (228/232 on 110) M6 last summer and better before that. My stock SS would do 30+mpg hwy if I kept it at 65-70. I'd use it to pick up my son across the state.

AnotherWs6

iTrader: (17)

Thanks, but I'm 99% sure the gears are stock. I have had the car in the air and everything looks unmolested. Now thats obv not a fool proof method. However when my speedometer says 70mph I am at 2,400 rpm and cruising right along with everybody else on the highway for the most part. The car doesnt smell like gas, it doesnt hesitate, it doesnt do anything abnormal. Im not dragging brakes because it rolls on slight hills unless the ebrake is pulled tight. I can slip the clutch at idle in first and it takes off fine. Its really weird. It's shocking to go 75 miles and see that half a tank of gas is gone.

M4N14C

iTrader: (3)

O2 sensors seem to be the biggest culprit then. I've read people who gained 5-10mpg just by replacing them.

Also, you have a M6? 2400rpm is way to high for 6th gear at 70...

AnotherWs6

iTrader: (17)

Might look into changing sensors, though I was planning on doing so with headers in the spring.

That's my rpm in 5th btw. 6th is pretty much useless unless I'm boogeyin, too many hills on nys

Jenson

iTrader: (32)

Well, problem solved. 5th@ 70mph. I use 6th at 50mph, plenty of pep even with my much bigger than stock cam.

ACCLR8N

Do you know anybody with scanning software? EFI-L, HPT, Actron, Autoxray? How about an Android phone and Torq app? I'm real curious what your fuel trims look like.

DemonicZ

My 98 Z A4 2.73s gets what I would call good gas mileage and I smash on this car. WOT, burnouts, 5-10 over the speed limit. I always seem to get 290-310 per tank. I recently took a trip out to Coalinga, its 340 miles or so and still had 1/4 tank when I got there.. Big mountain climb going to into California from Nevada. Once on I-5 between 75-85mph from stockton on out. Its not really hard driving but keeping those RPMs between 2400-2800 constantly. It costs me $80 for a round trip to Coaling and back. Thats 668 miles. 334 miles/9.3xxgal
Also car has no mods except Tune and muffler delete.

I drive my car alot, in the last 30 days I've driven over 1100 miles. and I live in a smaller city.

AnotherWs6

iTrader: (17)

I dont know anybody with any of those things. I did quickly take a peak at the torq app on my phone this morning. Well, the brief description of it anyway. Is this going to be able to tell me things like what you are talking about? It kind of looks like it just for real basic stuff. 5 bucks for the app and 12 bucks for the bluetooth obdII on Amazon........ for less than 20 bucks I will get both if it is going to give me good info.


And in 6th at 50? Do you have bigger gears in your car? Mine are stock 3.42's and 6th is pretty much worthless. That being said I have a set of 4.10's sitting in my garage, I just need to install them. I put 4.88's in the rear of my truck last weekend, hoping to get the front done this weekend, and then try to do the bird after that. Truck rear exploded so it was a priority.

ACCLR8N

Yes you are right $20 and you are in business. I have EFI-L and an Autoxray 7000 and I still bought the App and blue tooth adapter to play with. I have not played with the logging function, but I know that it will do it. You can log long and short fuel trims for each bank, front O2 sensor mV and injector duty cycle to get an idea what is wrong in your car. Because it sounds like something is. Possibly clogged catalytic convertor or a bunch of carbon build up in the top end. The data will rule out injector or spark issues.

JD_AMG

Theres your problem... I didn't want to ask from your first post, thinking that "there is no way this guy isn't using 6th gear", haha wrong.
He is right, 6th gear at ~50mph, use it, thats the only reason that extra gear is there, for gas mileage. I have never had an issue with it with a stock car on stock gears, and im still on stock gears with a H/C build and still have no issues using 6th.
Shift up as soon an possible, keep RPMs low and you will see much better gas mileage, these things have torque, use that to your advantage.

AnotherWs6

iTrader: (17)

Thanks man, I'm gonna order up the obdII right now. Oh, edit - do you have any idea which reader you bought? There are a lot of them on Amazon, i'd rather go for a prove one if possible.

JD_AMG - we could debate the merits or lack thereof of 6th all day, but there is no way i'm going to go from 12mpg to 27mpg by shifting into 6th. Since I drive my car so infrequently i do tend to shift a little later than need be just because I like the sound/feel. That being said, with my DD blown up I have had to drive the bird to work for the past week and a half. Didnt get a mpg reading last week, but I will be doing so today. For the first half a tank this go around I was def taking it easy, shifting real early, not playing with it. After getting 75 miles out of that half I was like **** it, driving style obviously has no ******* impact on this thing. I'm still taking it fairly easy, but have romped on it a few times since then. Don't worry, I'm not shifting at 4 grand every time on my way to work in the morning. But when traffic slows to 55-60 and were on a big, long fng incline 6th aint cutting it. All the highways around here are like that. Up and down, up and down, up and down. I just leave it in 5th because I get tired of shifting constantly during highway driving. Drivers are also the same way speed wise. Up and down, up and down, up and down. My head is ready to explode by the time I get to work. Everyone can be doing 75 one minute, then slow down to 50 the next for absolutely no fng reason. I'm stickin with 5th until the gears go in. I do appreciate your help and input though, thanks. I've been driving V8 cars in the same area for the past 15 years btw. I'm no spring chicken unfortunately.

JD_AMG

You may not see 27 (that is highway, 6th gear only kind of numbers) but I bet money you will see high teens, low 20s.
This is not a totally uncommon mistake people make with these cars, they don't realize how much 6th makes a difference. How do you think these cars were able to avoid gas guzzler tax? Skip shift feature + double overdrive 6th gear.
ERRR wrong!
Another common newbie mistake. Do NOT simply go by what the gas gauge reads, only use that to know when your low and need to fill up, otherwise its highly inaccurate to gauge gas mileage. If you want to know what kind of gas mileage you really are getting you have to fill completely up, reset the trip odometer and then the next time you fill up (fill up all the way again) divide the miles on the trip odometer by the gallons you put in the tank. Thats the ONLY way to do it.

Unless these are some monster hills you should have no problems leaving it in 6th gear @ 50. As long as you are above ~1000rpms you shouldn't have any issues cruising right along, uphill or not. Shift at roughly 2000-2500rpms, cruise in 6th, hello high 20s MPG, this is no secret.

AnotherWs6

iTrader: (17)

Dude, no ****. WTF are you talking about and who are you calling a newbie? I can use the gauge as a half assed rough estimation until I fill it up and do the correct calculation. If I go 60 fng miles on the first half I can reasonably assume that I'm not going to go another 250 on the second half. Holy Jesus dude. Thanks for teaching me something I learned 25 years ago.


You do whatever you like there home skillet. If I have to push the gas pedal halfway down to maintain speed in 6th or I can have it in 5th barely on the gas which do you think is going to yield better mpg? I dont give a **** what rpm youre at, its how much fuel your dumping in the motor at a given speed that determines efficiency. I so dont want to get into this.

TheBlueKnight

iTrader: (4)

I had all the import guys at my wife's work the other day in an uproar when I told them my Trans Am gets 31mpg on the hwy when I visit my parents. I top off at the gas station next to my house and it's 210 hwy miles to the gas station in their town. Right when I get there I top it off and calculate my mileage. I think last time I went down there I used 6.8 gallons. I'm full bolt ons and a mail order tune from Frost.

Half those guys at her work still don't believe it and think I'm making it up

Jenson

iTrader: (32)

Easy there AnotherWS6, JD is just trying to help. You will get better MPG by using more throttle and less rpm. No way around it. My hwy drive sounds a lot like yours, tons of hills, (Im right at the Appalachian foothills) and I can chug that thing along no problem. Especially with the torque'y 01-02 truck cam in these cars. And yes thats on a 3.42 rear gear.

If it will not pull to your liking in those situations, then you may have some issues like Acclr8n described. A clogged cat, O2's, rear O2's, MAF, or even a failing fuel pump could be the culprit. Ive got a stock MAF somewhere if that ends up being the problem, just PM me and pay for shipping and its yours. You can un plug the MAF and let it run in SD mode to test that for free. The pump usually makes some weird noises when they start failing, and headers will fix the cat/O2 problems.

P.S. My friend still holds the "record" in our crew, he had a red 00 WS6, filled up and went to Miami in it and got 33mpg. I still say there may have been a discrepancy in the pumps since obviously a different pump was used for two fill ups. I always use the same pump and fill it to the brim. Auto shut offs are unreliable even on the same pump as the pressure fluctuates.