Very Dissappointed With Gas Milage

Well over a 2 week average in the city with no A/C on I averaged 19.5 miles or $48 Canadian or $45 US That what it cost to 234 miles In my 99 3.8 Intrigue. Engine runs perfect no engine lite on, complete tune-up with GM plugs and wires. I am wondering if changing the oxegen sensor will help. What you think

well, it is a 3800cc engine. The GM's were never really known for exeptional gas mileage. Some tips tyo improve your fuel economy:

1.dont use a/c
2.change air filter
3. keep up tire pressure
4. Use cruise control whenever you can
5. make sure you change your oil AND tranny fluid on time (i know of wayyyy too many people who have NEVER changed their tranny fluid...EEK!)
6. Tune up....you did plugs and wires but yes oxygen sensors and pretty well anything in the evap system.....EGR, PCV if you have it (dont think that applies to the 3.8)

Real gas or 10% ethanol? Ethanol really does suck for gas mileage. Don't forget the fuel filter as well. You sound like you are taking care of things as it is now. City miles can be pretty harsh especially with a heavy foot (like mine).

Well, the 02 sensor is a big one, BUT the O2 sensor is ignored when you accelerate, which happens a lot in city driving, so it may not have a tremendous effect.

The PCV valve is a good idea, check for any vacuum leaks as well. If you remove the oil cap when the engine is running is there any suction? Does it change how the engine runs? If you place your hand over the whole can you feel any significant suction? These are indications of a bad PCV valve, or a bad vacuum leak. But heck its only like a 5 dollar part anyway, might as well change it.

Fuel filter is a good idea as well.

19.5 is honestly not that bad for the city, it sounds like you might do a lot of short trips as well, which isnt good for mileage.

I would disagree that GM cars arent known for their gas mileage, but thats a whole 'nother topic.

Did you look into the car's fuel economy before buying it? I have the 3.5 which is supposed to be more efficient I believe and it's MPG estimates were 19 city/27 highway, so 19.5 from the 3.8 sounds pretty good to me. Especially considering my mileage has dropped to 14.5 MPG for some ever-elusive reason. Like the guys said there's also the ethanol factor, and the summertime gas is warm and has expanded more than cold season gas, that makes a small but not insignificant difference in efficiency I've heard.

Jeez, I knew the dollar has been on a nosedive for years, but $45US is now only $48 Canadian??? Last I recall it was worth 1/4 or so more! Looks like somebody better get the US dollar to a motivational seminar or something!

14.5 is downright craptacular for a 3.8, unless you have a very heavy foot and do a lot of city driving. Even so, thats the worst Ive heard in quite a while.

19.5 is a decent number for city driving. You might take some short highway runs after filling up and see how you do.

After getting back from a road trip to Oklahoma, ill argue to the death that GM cars dont get good mileage. I got 28-29 on the way there and the whole time I was there running mostly 75-80 WITH the AC on. I also pulled a whopping 33 mpg on the way back drafting semi's almost the entire way.

14.5 is downright craptacular for a 3.8, unless you have a very heavy foot and do a lot of city driving. Even so, thats the worst Ive heard in quite a while.

19.5 is a decent number for city driving. You might take some short highway runs after filling up and see how you do.

After getting back from a road trip to Oklahoma, ill argue to the death that GM cars dont get good mileage. I got 28-29 on the way there and the whole time I was there running mostly 75-80 WITH the AC on. I also pulled a whopping 33 mpg on the way back drafting semi's almost the entire way.

One of these days I'm going to drive 50 mph on the interstate and see what kind of mileage I get.

I just did a 350 mile trip, interstate on the way there, county, winding, highway on the way back, and about 110 miles city, while I was there and got 26.2 combined. Usually, I get about 30-31 mpg on interstate travelling about 75-80 mph with the AC running.

One of these days I'm going to drive 50 mph on the interstate and see what kind of mileage I get.


I sense sarcasm, but in all reality I think youd get in the high 30s, possibly even 40s. For gas mileage you want the highest gear with the lowest rpms. 50mph would put you in 4th gear, probably barely above idle rpms.

Or were you trying to imply that because I was drafting I was going slow? I assure you that was not the case.

Glad I found this forum and this thread in particular. Been checking out some issues on my Intrigue for the last couple of days.

I get between 18 and 19.5 mpg on my daily city commute ( ~ 18 miles one way - "freeway" route either at a standstill / crawl or up to 75 mph).

On the highway, I don't think I've EVER gotten more than 22 mph. I don't drive like a grandma, but not like a total maniac either (usually keep it around 70 - 80 mph on the open freeway).

I have gotten this kind of mileage since I bought the car new in 1999. Had the dealer look at it at first but got the "that's about average for this car" response. Wasn't happy with that but didn't feel like spending big $$$ to have them look for something elusive.

Somewhat relieved to see many on this forum have the same experience. Just wish I could get nearer the 27 - 29 mpg on the highway as suggested by the sticker. I guess that why they say your mileage may vary!

Dude! I would be replacing O2 sensors, spark plugs, wires, air filter, PCV, and DEFINITELY run some synthetic(Amsoil) in the engine and tranny. Since ethanol is in my gas everwhere here I used to get 30.x idriving the flat roads of NC. You should be getting very close if not better than my 3.5.

Almost sounds like a computer isn't reading something right. Does your engine warm up all the way to the halfway mark? T-stat could be stuck open.

Does your car feel fairly fast?

Hopefully someone else will chime in with something more tangible for you.

What is your rpm at highway speed? It should be around 2000 rpm for 70 mph.