I'm little bit worried when i look at my fuel consumption. I'm worried bigtime but my cadillac garage here in the Netherlands said the fuel consumption is normal with these cars!!??

I mean, 9.41miles to the gallon. that's 10.6 gallons lost in 100 miles..that's not normal, it's not a streetmachine with 500+bhp

Ok, we're talking city driving here, no highway, yes airco is on from time to time. But still, isn't this just a little too much.

When driving on a highway it does 21 to 23 miles to the gallon.

Can you guys give me your fuel consumption experiences with a sts northstar from 1994-1996.

There is definatly something wrong, or you are really driving hard. My SLS gets 18 city and 26 highway, your gears are steeper, but it shouldn't be causing that much of a difference.

1. When was it last tuned up?
2. Are you getting any codes?
3. Is your transmission going into overdrive?

That is really low.... In the most ridiculous city driving, I've never seen below 17.5.... never.

Something is definitely wrong... fuel leak somewhere???

Does it run okay???

I had a leak from a fuel pump fitting once.... it leaked pretty good when running, but not hardly at all when parked.

I BLEW a fuel line on the 79 Eldo, years ago... that drastically reduced my mileage, heh heh... I made it about 10 miles, using a full tank of gas. Coasted into a semi-truck service place, and they fixed it. What a stinky mess....

Just random thoughts.... but I would say, something is not right.... the only reason I share these stories is, the cars ran fine, even the 79, gushing fuel... so it's possible you're leaking, if the car is running good...

Something is definately wrong. My '73 Eldo with a 501 got better than that. Open the intake again and turn the key ON to pressurize the fuel system, but DO NOT crank/start the engine. While pressurized, check the fuel rail and FPR for leaks. Also put a fuel pressure guage on it and see if it holds pressure after key off. If not, perhaps a stuck open injector.

Not to post steal but ever since I've had my car my avg around town is anywhere from 12-14mpg. My recent 700 mile highway trip I avg 23.8mpg. I go WOT once a day I would estimate. The car has new plugs, wires, cleaned out intake and TB, cleaned egr, fuel filter, air filter. Should I replace the FPR? I've checked it the way described but have seen no leakage. Any ideas?

Should I replace the FPR? I've checked it the way described but have seen no leakage. Any ideas?
No. If it ain't broke, don't fix it.

That is really low.... In the most ridiculous city driving, I've never seen below 17.5.... never.

Something is definitely wrong... fuel leak somewhere???

Does it run okay???

I had a leak from a fuel pump fitting once.... it leaked pretty good when running, but not hardly at all when parked.

I BLEW a fuel line on the 79 Eldo, years ago... that drastically reduced my mileage, heh heh... I made it about 10 miles, using a full tank of gas. Coasted into a semi-truck service place, and they fixed it. What a stinky mess....

Just random thoughts.... but I would say, something is not right.... the only reason I share these stories is, the cars ran fine, even the 79, gushing fuel... so it's possible you're leaking, if the car is running good...
What kind of check and/ or fix did you perform? I posted some time ago about my 1994 STS and the faint gas odor I smell in my garage after shutting off the car, so maybe I have a leak that occurs only when driving, too. I get only 12-14 MPG in city driving, driving about 10 miles a day.

DR, the easiest thing to do is what Ranger suggested.... turn the key on, but don't start the car. You may be able to hear the fuel pump running.

The idea is that when the car is parked & shut off, the fuel pressure system is not pressurized.... so there's little to no leaking.

Now, with the key on, car not running, it WILL run the fuel pump and pressurize the fuel system. Lines, injectors, filter, everything. So, with the key on, go over the thing very carefully, and try to find the leak.

If it's a leaky injector, that's different.... those would have to be checked individually.

But step one is probably to eliminate some sort of exterior fuel leak. The smell will probably take you in the right direction.

DR, the easiest thing to do is what Ranger suggested.... turn the key on, but don't start the car. You may be able to hear the fuel pump running.

The idea is that when the car is parked & shut off, the fuel pressure system is not pressurized.... so there's little to no leaking.

Now, with the key on, car not running, it WILL run the fuel pump and pressurize the fuel system. Lines, injectors, filter, everything. So, with the key on, go over the thing very carefully, and try to find the leak.

If it's a leaky injector, that's different.... those would have to be checked individually.

But step one is probably to eliminate some sort of exterior fuel leak. The smell will probably take you in the right direction.

Thanks a lot. I'll give it a shot this weekend and report back.

I'm little bit worried when i look at my fuel consumption. I'm worried bigtime but my cadillac garage here in the Netherlands said the fuel consumption is normal with these cars!!??

I mean, 9.41miles to the gallon. that's 10.6 gallons lost in 100 miles..that's not normal, it's not a streetmachine with 500+bhp

Ok, we're talking city driving here, no highway, yes airco is on from time to time. But still, isn't this just a little too much.

When driving on a highway it does 21 to 23 miles to the gallon.

Can you guys give me your fuel consumption experiences with a sts northstar from 1994-1996.

Hi fellow Dutchman,
just in plain Dutch, our STS does in the city "1 op 6" and has an average of "1 op 8" so that would be 14.2 miles/gallon and 18.9 miles/gallon if I'm not making a mistake on calculating.

Any loss of power?

My '02 has a plugged cat and the mileage dropped into the 12-13 MPG range... Car runs like a pig though... It would have to be really plugged to get you into the 9's... To a point where I doubt it would run.

If the engine is running to rich you would notice a change in performance.I have a 93 N* vin 9 which are gas guzzlers :alchi: .Im getting 15 city 28 hwy when I got the car it was getting 11 city 19 hwy :thepan: it was running very rich.In very heavy city trafic your MPG can go way down but hwy it should be a prety much a true avarege yours is very low unless you are running at very high speeds 85 +.

With a N* running that rich it wouldnt take much peddle to get that engine screaming.Wich was the case with my car when I got it.

This is what it was running like performance was way up but what told me it had a problem was on the highway at steady a cruiseing speed there was a slite engine cutout.The ecm was catching the rich mixture and compensating for it thus a split sec of fuel shutoff.

The cause was the last O2 sensor was giving the ecm a false reading causing
the rich mixture. The only way we found the cause was to put the car on a
computer diag in the shop and my mech who owns a N* new what the correct
ecm controls readings should be and replaced O2 sensor BIGO MPG up 50% :thumbsup: .Of course the awsome power the engine had was back to normal.

Just my .02: If in the city, you mean stop and go every block and very short trips so that the engine hardly gets up to temp, I would say that mileage is acceptable. Your highway measurements really measure it's efficiency. Are there any codes that would suggest emmission or spark failure. 12.5% reduction for each dead cylinder. I think you just live on a hill..No?

I agree with delzy, if you have a lot of constant stop and go traffic the mileage will suffer as a result. 9.4mpg would be about what I'd expect if you had to stop and then accelerate every block, or if you spent a LOT of time sitting and idling.

Something is definately wrong. My '73 Eldo with a 501 got better than that.

500

check your air filter and make sure that your brakes aren't dragging.

Air filter will have no effect on a fuel injected engine. A dragging brake will however.