10 mpg?

["Turbo-T"]

Holy shit I think my Buick drinks fuel worse than an alcoholic drinks alcohol.

Today I got paid and the fuel gauge was on 1/4, yet I've only driven the car 107 miles since the last fill up. I figured maybe the gas gauge was reading wrong.

So i fill it up, and it took 10 gallons to put it at full. If I'm not mistake, that's over 1/2 of the gas tank!!If my calculations are right, it says I'm only getting 10 mpg. That seems a bit unrealistic for a V6.

Now granted, my car has really only been driven short distances since filling up, it has 60 lb injectors, I also have a 2800 stall, but I have stock sized tires and a stock rear end with the factory BRF200-4R trans. The car has barely seen any speeds above 35 mph since the last time i filled it up. My e brake isn't dragging, that I know of.Car weight is roughly 3700's with me in it.

My AFR's are usually in the upper 13's to lower 15's. My car does emit stinky exhaust that smells a tad rich, but then again my car doesn't have a cat. Also i have a turbo tweak chip which i am told burns a tad on the rich side.

What gives? Shouldn't the fuel mpg be a little better than 10 mpg?

 

[TurboHungry]

Considering my V8 4x4 almost 6000lb full size blazer gets 12mpg driving similiar to how you described I would say you could do better. I mainly do short trips like that in the GN too but since the speedometer is way off (so odometer is too) I can't factor mpg .

 

[whitehot1]

If i remember correctly 17 mpg city was stock gas mileage, so yeah 10 mpg is really bad.
A few things you could do.
1. replace the fuel and air filters, pcv valve, valve cover breather depending on how old they are.
2. replace or clean spark plugs.
3. check tire pressure.
4. remove any unnecessary items from the trunk of the car.
5. go light on the gas pedal when taking off from a stop.

 

["Turbo-T"]

Air filter is a K&N, I cleaned it maybe less than a year ago and probably don't have 3000 miles on it since, if that. I'll check it and see that it didn't get clogged up since then.

Plugs are almost as old. I did replace them less than 1000 miles ago.

You could be right on TP, I'll check that out.

As far as taking off from stops....i will admit here lately I've gotten on it a little. What I mean by that is I wouldn't quite get into boost, but on the vac gauge, the needle would go to about the 0 and stay there. So yeah I did have some acceleration starts but no boost starts.

I also will admit there were a lot of short stop and go trips less than 2 miles per commute. I also would let the car idle in the drive some mornings when the temps were in the 20's and 30's.

Even then I can under stand with all i have done, fuel mileage will be reduce, but unless my tune were in the 11's all the time, I really can't foresee how does one but thru 10 gallons of fuel in only 107 miles?

 

[sscamino]

Just for the heck of it check the injector harness for any warn bare wire on the under side especially above the EGR . If the inj. wire heats up it will soften and lay on egr .When it grounds on the egr or intake,this makes the injector go wide open and have a rich condition.

 

[L8TRH8R]

I'd hope you'd see much better then that!

 

[mikestertwo]

With the type of driving you do and the cold weather your mileage isn't surprising. The combination of short trips, low speeds and cold weather kills mileage. The engine never has a chance to warm up. If your not running at least a 180 degree thermostat you should be.

 

[novaderrik]

short trips kill mileage.
idle time kills mileage.
big aftermarket injectors can kill mileage.
a heavy right foot kills mileage.
running in cold weather kills mileage.

 

[williamsGN]

Fill it up, take it for a long drive being modest on the pedal, after 100 or so miles, refill and divide miles by gallons just filled. Your results may be better. I get 14 or so driving around town getting into it occasionally, 18 or so on the freeway. As I've always said, people claiming 25+ mpg on these cars need to go buy a calculator. If you're daily driving in low temps, you should consider a 180 or 195 stat.

 

[SHADOWII]

if you have a fuel rail gauge chick to see how fast it goes to zero psi. then check the dipstick for a fuel smell in the oil. You may have a leaking injector that can wash the cylinder down. Ask me how I lost my original engine in the 86!

 

[DavzGN]

Check your O2 counts and blm values. A bad O2 or a vacuum leak can kill milage too.

David

 

[zhorner]

I would expect something to be wrong. all things considered 10 mpg is low for a gn with your mods IMO. I would do like "williamsGN" said. Fill is up, cruise around 100 or so miles then refill and see. I have very similar mods and get 17 full-empty with a lot of in town driving.

 

[GNRick]

I get 12 in city with same mods as yours. On my other car when the milage dropped from 15 city down to 10 I changed the fuel filter and that fixed it. Ever see the black specs in the bottom of a gas can? I don't know what that is but I'm sure it clogs up your fuel filter eventually.

 

[whitehot1]

What spark plugs are you using?

How old is the o2 sensor? Like mentioned the o2 sensor will definately lower gas mileage. Rockauto has good prices on o2 sensors,even with shipping added they are cheaper than the autoparts store prices.

 

[NorEaster]

Fill it up, take it for a long drive being modest on the pedal, after 100 or so miles, refill and divide miles by gallons just filled. Your results may be better. I get 14 or so driving around town getting into it occasionally, 18 or so on the freeway. As I've always said, people claiming 25+ mpg on these cars need to go buy a calculator. If you're daily driving in low temps, you should consider a 180 or 195 stat.

I have got 25 mpg after my bailey chip install with lean cruise activated. And belive me, I know how to figure out mpg.

 

[highboostgn]

I must get around that...after a week of 8 miles round trip back and forth to work i run a tank down to half

 

[V6sleeper]

With my car it all depends on how hard is the right foot,i can get as bad as 9 mpg and as good as 20 mpg..ive actually tested it....any of my other cars dont have that wide of a range no matter how hard i beat on them...

 

["Turbo-T"]

To answer some questions....

Running AC43TS plugs, with less than 500 miles on them.
O2 sensor is at least 5 yrs old and it's the AC Delco purple wire brand
I'll try checking the cross counts.
Fuel filter I changed about 2 yrs ago, probably haven't even put 10k on the car since the change.
I do have a fuel psi gauge but it's electric. Will have to hard wire it so it's on all the time to see how fast the rail psi goes down.
I do have a 160 degree T stat in the car. I never changed it b/c it seems everyone claims the 160 t stat is the way to go. i can try changing it.

I will also try filling it up and going on an extended cruise to see if the mpg gets better.

 

[L8TRH8R]

Making boost should be your biggest fuel consumption problem, if you're driving granny style and getting 10mph, something up. My experience is similar to the stated above, my car can get any where from 5-28 mpg depending on my rt foot.