: Fuel mileage (Holy cow!!!)



Dadillac
06-06-06, 10:23 AM
Up until April 28th, I had a 38 mile commute one way to work. Twenty eight of those miles were run on the NJTP. My fuel mileage was always around 21 mpg. Now that I am doing nothing more than short trips, and suburban type driving, my fuel mileage plummeted to 13 mpg. What a major difference. The only plus side to this is I only have to fuel up every two weeks now, instead of every 4-5 days. Damn

Don

parts68
06-06-06, 05:56 PM
with that kind of fuel economy you should have a tire wear issue

AlBundy
06-06-06, 06:59 PM
Did you take that Tornado out of the intake???

Dadillac
06-06-06, 08:53 PM
Did you take that Tornado out of the intake???
Nope, it is still there. If this kind of mileage keeps up, I will remove it, and see what happens. I will remain positive about it.

Don

Dadillac
06-06-06, 08:53 PM
with that kind of fuel economy you should have a tire wear issue
Please explain.

Don

parts68
06-06-06, 09:27 PM
lead foot = constant tire smoke

AlBundy
06-06-06, 10:35 PM
Nope, it is still there. If this kind of mileage keeps up, I will remove it, and see what happens. I will remain positive about it.

Don

Well while I was trying to change my TB for one of eldorado1's I found a Tornado in my intake right under my cars nose:eek: . In perfect condition nice and shinny. As far as better MPG, I wish I knew considering I didn't know it was there in the first place. If my MPGs start to suffer from its removal I will post back:thumbsup: .

dp102288
06-07-06, 09:20 AM
The only plus side to this is I only have to fuel up every two weeks now, instead of every 4-5 days. Damn

Don

You refuel less with lower MPG? Why, because of shoret trips and less total miles?

My Eldo gets 13 MPG. Very frustrating.

Dadillac
06-07-06, 10:59 AM
lead foot = constant tire smoke
I am not doing that kind of driving. Just the basic ordinary driving, just no highway, and alot of around town. As far as fueling less, yes, I am putting on way less mileage. I used to do about 425-450 miles per week, now it is around 100 miles. A tank of gas used to get me between 325-400 miles, depending on driving habits, and how long I waited to refuel. The last tank was only 220 miles. A huge difference.

Don

auroradude
06-07-06, 04:45 PM
Try and coast as much as possible. Dont drive the car feathering the gas all the way up to a stop and then hitting the brakes semi-hard to stop at the stop sign. My mother does that all the time and it drove me insane...my dad does it too but not as bad.

I dont even use the brakes, very rarely. Heres what you can do. On backroads lightly accelerate up to 20mph over the speed limit if its a secluded area (all are back here) and just let it coast all the way to the stop sign. You get much better INST mpg obviously and do NOT tap the brakes the whole way down. I hate when people do that. Just start pressing em lightly when you are getting close, just enough so that you are barely even applying them.

Oh yeah and replace them O2 sensors. Doing that at 85k miles yielded me 100+ miles extra to the tank (now getting 370 out of a tank instead of 275 or thereabouts). You do the math.

Also take out that stupid "tornado" contraption gimmick. Some people have more money than brains.

If you are driving all city let me recommend you put the transmission in "3" third manual to disable overdrive/tcc from engaging. That should be better for the transmission as it doesnt have to shift as much. I used to leave it in D no matter what and going 20mph it would lump into lockup and lope around at 1300rpm. Lame.

Another pointer..if you are going slow in town or whatever ( < 15 mph or so ), do NOT hit the gas and then the brake repeatdly (when traffic movse up a little bit..you know) So many people do this i notice. Hit the gas, hit the brake and keep repeating 20 times in a traffic jam. Just let up off the brake and let the TC move you. When you keep hitting the gas it disengages the TCC from the driveline and has to re-engage it when you hit the brake to keep the engine from stalling. Correct me if im wrong but i believe this would save gas if you make it so it doesnt keep doing this all the time. Less heat, less mechanical changes = longer life also.

Dadillac
06-07-06, 05:10 PM
Oh yeah and replace them O2 sensors. Doing that at 85k miles yielded me 100+ miles extra to the tank (now getting 370 out of a tank instead of 275 or thereabouts). You do the math.
Is that true? I know very little about the emissions system. I always thought that the O2 sensors either worked, or didn't work. So they gradually go bad? Taking mileage with them? They can be bad enough to affect mileage, but not throw a code? Please, I need more info.

Don

thu
06-07-06, 06:18 PM
I have heard of the O2 sensors failing and not throwing a code. In fact, one of the members here report that recently.

auroradude
06-07-06, 06:32 PM
Absolutely, mine did not throw a code. I know of someone who had 200k miles on their aurora and it threw a code then. Thats far too late.

How many miles do you have? I'd say if its 50k+ replace em definately. You WILL see an improvement. Just think if everyone did that how much gas would be saved.

AlBundy
06-07-06, 08:04 PM
Nope, it is still there. If this kind of mileage keeps up, I will remove it, and see what happens. I will remain positive about it.

Don

The reason I asked about it is while taking it out of my intake I noticed that it could easily turn sideways and restrict flow so I would check it just to make sure. :thumbsup:

GreenMachine
06-07-06, 09:25 PM
in heavy city traffic I get real low, probibly 13, but around the suburban driving I get atleast 14-15. 98' Deville and I have my moments of pedal pushing, whats the use of all that power if your not going to use it sometime :)

94greencaddysls
06-07-06, 09:52 PM
I do mostly city and am getting around 13-15mpg. I replaced the rear o2 sensor last week. It does not set a code city driving but it does on the highway after a couple minutes. The voltage was consistent .45 so something was up with it. I have not noticed an increase in mileage from replacing it though.

auroradude
06-08-06, 12:57 AM
Only replacing the one in the front counts for mileage. I forgot to add that. You might as well not even replace the rear one, but if you dont care about the money then replace em both. I think you guys have 4 of them on the STS haha...i have 2.

chevyorange
06-08-06, 03:38 AM
Do all STS years have FOUR?? Does the "replace only the front one" still count?

I have a new engine with poor milage but runs great (rich?). 91k when the engine was changed on original O2s. I think this is my next project.

I have the service manual so it should not be a headache - unless I need to do two or FOUR???? :)

auroradude
06-08-06, 04:57 AM
Just do the front two and see how that works. The ones after the cat dont do anything for gas mileage i believe but may lead to early cat death. Take your pick.

dp102288
06-08-06, 08:40 AM
How much is ONE O2 sensor? I don't want to get gouged at the local tire mart.

94greencaddysls
06-08-06, 01:04 PM
Car's pre-OBDII have only two o2 sensors. So pre-96 have only two. The ones around the cat are only there to insure it works. So my rear o2 is fairly important

chevyorange
06-08-06, 01:20 PM
Ok, at 93k with a new engine, and original O2s on my 1994 - I will replace both of mine. Thanks for the info.

auroradude
06-09-06, 10:09 AM
GREAT. Make sure to repost here when you get 100 miles a tank back

chevyorange
06-09-06, 12:14 PM
I will. I can already picture it on my DIC!

Thanks!

Tommy Deville
06-09-06, 07:59 PM
U know if that Tornado made a real cool turbo sound I could see leaving it in there, but ponder this, That thing is spinning at god knows how many RPMS lets say it breaks apart and throws "a fin" as we say in the biz, that piece of metal gets sucked into your head, your engine is toast my friend, heads vavles, pistons, its over Johnny.
Anyway My Deville goes form 12.5 to 16 with a mix of around town driving and highway driving, I dont like how my car feels in 3rd gear it feels like it pulls too hard in 3rd gear, but mabe thats what it suppossed to do
I need to WOT havent done it in a real long time.

94greencaddysls
06-10-06, 12:19 AM
The tornado itself doesnt spin, it spins the air. Or thats what the concept is as if it helps.

El Dobro
06-10-06, 11:33 AM
That's interesting that the tornado is spinning the airflow. If you have a MAF sensor, it has a honeycomb so the airflow is straightened out.

Dadillac
06-10-06, 09:29 PM
That's interesting that the tornado is spinning the airflow. If you have a MAF sensor, it has a honeycomb so the airflow is straightened out.
The Tornado is after the MAF. So it will still spin the air into the intake. Don't know if it is working or not, but it is there, and will probably just stay there. Also, I noticed we now have 10% Ethanol fuel here. Is that at least partly responsible for lower fuel mileage?

Don

Ranger
06-10-06, 09:52 PM
The Tornado is after the MAF. So it will still spin the air into the intake. Don't know if it is working or not, but it is there, and will probably just stay there. Also, I noticed we now have 10% Ethanol fuel here. Is that at least partly responsible for lower fuel mileage?

Don
Yup, 30 - 50%. Probably good for about 1 MPG Don.

Dadillac
06-11-06, 11:11 PM
Yup, 30 - 50%. Probably good for about 1 MPG Don.
Well, with that little extra, I would be at about 14 mpg city. Not too good, but WTF. I am just going to see how I do with this current tank, and see what's up. Maybe I just got a bad tank of gas.

Don

boricuacaddy
06-12-06, 09:52 AM
I do a lot of city driving. all stop and go. My car is getting 13.6 MPG. I did go on the expressway this weekend and my MPG shot up to 22MPG. It was a short trip, about 75 miles one way. I am amazed that it had shot up that high. I guess that 17MPG in the city that is suppose to be rated at must be for driving in a little town, where there is hardly any traffic. Not driving around Chicago.

David

thu
06-12-06, 12:23 PM
Again, it's all about the right foot.

chevyorange
06-12-06, 12:30 PM
I have a judicious right foot... I have a feeling that new O2 sensors will help, they'll arrive tomorrow!

auroradude
06-12-06, 12:42 PM
You putting em in yourself? I know the O2 sensors will help...your going to laugh when you try driving afterwards...lol

Oh yeah, enjoy having to only put 2 in. The 1996+ northstar engines have 4.

chevyorange
06-12-06, 01:14 PM
You putting em in yourself? I know the O2 sensors will help...your going to laugh when you try driving afterwards...lol

Oh yeah, enjoy having to only put 2 in. The 1996+ northstar engines have 4.

You're the one that told me to put them in, why are you laughing at me? Do I need to reset anything that I don't know how? Does the computer take a dump on me or something? Help a brother out!

i have the service manual for my car - the front O2 looks EASY, the rear looks HARD!

auroradude
06-12-06, 02:40 PM
I'm not lauging at you man, i said you are going to laugh when you start driving after you find how much more MPG you are getting.

Nope no resetting anything simply remove old ones and plug in the new ones. The one in front of the engine is the one that controls the gas mileage. The back one just checks to make sure they are working i think -- still want to replace both though

chevyorange
06-12-06, 02:42 PM
AH, good. I was worried there was some critical step I might miss.

Shoud be gettin' them tomorrow. Can't wait to pick up a few MPG!

94greencaddysls
06-13-06, 06:14 PM
It wouldnt be a bad idea to go into the computer and reset fuel trim to default values and let it adjust. Im going to go ahead and break the bad news to you though...the rear is next to impossible. My replacement bosch was about twice as big as the acdelco so I didnt get it in fully.

chevyorange
06-24-06, 03:11 PM
It wouldnt be a bad idea to go into the computer and reset fuel trim to default values and let it adjust. Im going to go ahead and break the bad news to you though...the rear is next to impossible. My replacement bosch was about twice as big as the acdelco so I didnt get it in fully.

I did the front one last weekend, and was thinking of tackling the rear this weekend. Can you get at the rear one without too much stuff in the way? I haven't even seen it yet.

Did you get that rear sucker in?

fubar569
06-24-06, 04:38 PM
then why can i only locate 2 on my 97 deville? there's one front and one rear...and that's it?

chevyorange
06-24-06, 04:41 PM
Yeah, 98 starts with the 4 o2 deal.

How hard was it to replace your rear o2?

Ranger
06-25-06, 09:13 PM
then why can i only locate 2 on my 97 deville? there's one front and one rear...and that's it?
There is one on each exhaust manifold, one pre-cat and one aft-cat.

100
06-25-06, 10:43 PM
I thought you could check the quality of a O2 sensor by checking its cross count rate... I thought if you check the count rate and if it goes 5-10+ while driving, it should be OK. Am I missing something?

Tommy Deville
06-25-06, 11:12 PM
My deville has 103k on it most of my driving is extremly short distances, when my mileage gets around 12.5 mpg I WOT and take it for a spin on the highway to get it back around 14
when i hit the road on long trips i'm a left lane driver 75 85 MPH range so i i average about 17-18 MPG some times i break the low 20's 21MPG if everything breaks right.
I think i'm gonna bring it in for a tune up and have the o2 sensors changed. Just a basic tune up on this car is expensive, I can imagine how much it will cost to chane the o2 sensors. but it will be nice to get 15 16 MPG around town again and mid 20's on the highway

fubar569
06-26-06, 02:37 AM
There is one on each exhaust manifold, one pre-cat and one aft-cat.

i will doublecheck this...i swear i didn't see anything else...but could be smoking crack again...

*EDIT* - checked with a couple online parts places...indeed apparently the "upstream" sensors must be the ones in the manifolds i didn't see...2 required....

chevyorange
06-30-06, 10:08 PM
OBD I Northstars use two (one front one rear). I have replaced the front one but have been waiting to hear from anyone that has done the rear, the book makes it look considerably more difficult.

cadillacdrvr8692
08-08-06, 12:24 PM
i believe auroradude is right...thats what ive been doing since ive got my cadillac and yes it does help i can go from 13-17 mpg's then when im coasting the correct way it will shoot up to 46-52mpg's!!! but as far as the tornado thing i was getting like 9-12 mpgs in the city and after i installed some other called the TURBNADO which i purchased on ebay for 10$ vs the tornado from autozone or Oreillys for 70$!!! ive been getting more milage on my trips since installation but who knows!!

GreenMachine
08-08-06, 01:41 PM
well the tornado or what not might obstruct airflow causing the car to run more lean....which could actually improve mileage in coasting and cruising situations. It will most certainly if its doing that make acceleration sluggish at times.

awfulpotent
08-11-06, 10:48 PM
if you want good fuel mileage buy a neon

dkozloski
08-12-06, 01:04 AM
If you want good milage do like everyone else, lie about it.

BIll_Bixpy
08-23-06, 02:04 AM
I gotta 95 concours w/a OBD I north* and I definately have four O2 sensors. I went the cheap route and only changed front 2(on the manifolds). I'm getting 18 city mpg now(up from 14) constant stop and go idling going into curb stores and all. :) 161k and going strong!!

ibarria
08-23-06, 09:25 AM
if you want good fuel mileage buy a neon

Neon?? nahh Toyota Prius.. even b:bighead: :want: :stirpot: :thehand: :worship: :thepan: :bouncy: :rant2: :crybaby: :) etter huh?

I_Finally_Have_A_Cad
08-23-06, 11:19 AM
Hey I also have a neon. It is an ugly purple, two door with a manual trans. I average 44 mpg in the summer.

It's great, I have the perfect balance of a high mpg turd and a gas guzzling luxury sedan.

Unfortunately, my wife doesn't like driving a manual, so I get stuck with it while she travels in style. I geuss I need a better balance of two devilles. All I need now is 20-40K dollars.

clarkz71
08-23-06, 01:10 PM
I gotta 95 concours w/a OBD I north* and I definately have four O2 sensors.

I would have to see that to believe it. I have a 95 Eldo and it only has 2 sensors, one in each manifold. I also have the 95 Factory Service Manual and it say's......"Two sensors are mounted in the exhaust system, 1 in each manifold". I've only seen 4 sensors on OBD 2 cars in all my years as an auto technician. What's the production date on the door decal, maybe you have a late production car that has OBD 1 but came with 4 sensors for some reason.

chuck1221
08-27-06, 10:38 AM
I have a big 97' deville and the worst mpg I have had is 20, that was in the dead of winter (wisconsin) and driving 70 - 80 mph. This summer I have been getting anywhere from 23.5 to 25.5. My average trip is roughly 20 - 25 miles non-highway diving but not stop and go. I can't complain. been a good car to me. Just turned 130,000 as I pulled in the garage yesterday. Goodluck with your car.

chuck

red_sand00
10-19-06, 07:10 PM
Speaking of fuel economy and the "tornado"..If I remember correctly Mythbusters did a stick on fuel saving items and the tornado did absolutely nothing..It actually made the fuel economy worse if I remember correctly..One would think that when the folkz design an engine they would design it to get the best fuel economy possible.. Just some little thoughtz..

Zorb750
10-19-06, 09:02 PM
Nope, it is still there. If this kind of mileage keeps up, I will remove it, and see what happens. I will remain positive about it.

Don

Popular Mechanics isn't positive about it.

Anyway, I can drive normally and keep my car under 2200 RPM all day long, too many Northstar drivers are rev heads (myself included - I CAN keep it under 2200, doesn't mean I do)

Dadillac
10-20-06, 09:38 AM
Popular Mechanics isn't positive about it.

Anyway, I can drive normally and keep my car under 2200 RPM all day long, too many Northstar drivers are rev heads (myself included - I CAN keep it under 2200, doesn't mean I do)

I am a N* "rev head" also. I use the throttle probably more than I really should. But I am not doing it all the time, just more than I should.

As for the Tornado; it is still in the car. That is only because I am too lazy to remove it, and plug up the hole I drilled in the intake tube. It has done nothing for mileage, and I suspect it has hurt acceleration a little. I will be removing it when I decide how to repair the intake tube.

No matter what folks tell me, sometimes, I just have to find out for myself. This time, everybody was right. But sometimes folks are wrong. And that is how I find things out. Just because something doesn't work for some, doesn't mean that it won't work for others. So I spent like $50 on this thing (I can't remember exactly) and it was a failure. Not the most expensive mistake I made. I will probably put it down in the basement, and keep iy for future projects. You never know when a piece of stainless will be handy.

Don

dp102288
10-20-06, 10:57 AM
^^ I hear you. Even if someone tells me "that won't work' I have to see for myself. At least you did find out, and it didn't cost you more.

infin1ty
10-20-06, 08:03 PM
Toyota also now makes a Camry hybrid that gets ~40MPG combined with ~200HP. All of the bells and whistles, but no WOTs. GM needs to do some serious R&D to regain their market share.

AlBundy
10-20-06, 08:50 PM
I still have mine that I found in my intake by mistake when I installed eldorado1's bored TB. I keep it incase the forum decides its going to give a prize to someone. I think I will try and sell in on ebay when I try to sell my original TB.