Gas Mileage

[57chevyragtop]

Originally Posted by 57chevyragtop

The Poll is interesting, would like to see the same type poll for the 3400 engine. I know my 3400 mileage is poor compaired to what I have read hear in this forum. 02 63k 16mpg 100% city...but I also don't drive more than 6 mi at a time mostly and figure that is why..New plugs and wires Air filter (standard AC) I also can't see how a fuel filter if it needs changed would effect mileage, but performance yes if starving for fuel. If you can give me reason to change filter and why it would effect mileage I'm listening. Isn't fuel pressure more the consideration?

Finally got that 330 mile trip in...98% highway and mileage was 34 MPG on the nose...just where I was hoping it would be. Very good for this size car in my opinion...I have concluded that short in-town trips cuts that down considerably so I am relieved that I do not have any problems concerning fuel system...2002 IMP 3400 63500mi. Checked twice, 165 mi each way..

[CT Tim]

Anyone know if there is something that could both be causing my poor gas mpg(13-14) and at the same time affecting the ac?- (it's better than nothing but the air never gets that cool even durring highway driving).

Tim

[57chevyragtop]

Originally Posted by CT Tim

Anyone know if there is something that could both be causing my poor gas mpg(13-14) and at the same time affecting the ac?- (it's better than nothing but the air never gets that cool even durring highway driving).

Tim

A little more info would help ie: mileage, year, 3400, 3800, recent tune up info if any, and against what type of temps are talking 80, 90+...Off hand there could be a leak in air sys or low on R134 refrigerant or perhaps improperly charged...compressor could be dragging or bound up. for the mileage though I would look at plugs and wires first...

[CT Tim]

2000ls/3800/100k miles/recent tune up -new wires,plugs,changed air filter,fuel filter,and complete radiator/coolant flush, temps anywhere from 70 on up.
I appreciate the response but I'm guessing this may be a rather costly fix. I mean the gas mileage issue in particular-for a car like this I should be getting more than 13-14mpg even if it is alot of city.

Tim

[57chevyragtop]

Originally Posted by CT Tim

2000ls/3800/100k miles/recent tune up -new wires,plugs,changed air filter,fuel filter,and complete radiator/coolant flush, temps anywhere from 70 on up.
I appreciate the response but I'm guessing this may be a rather costly fix. I mean the gas mileage issue in particular-for a car like this I should be getting more than 13-14mpg even if it is alot of city.

Tim

Well you may not be as far off the norm as you think, I have the 3400 new plugs, wires, etc. and I was getting 13.5-16 but very little highway 20% or so. As mentioned above I just did a 330 mile round trip and got 34 MPG 98 % highway...if both were 50/50 highway/city thinking around 23-24MPG would be the case. Only thing you can do to be sure is do a long highway only test of say 50 to 100 miles for your own comfort before you spend good money going after a solution you don't need. Those are my thoughts....dave

[CT Tim]

As far as the ac goes, I used a meat thermometer, the digital kind, and placed in the various ac vents while it was on full blast, I was receiving a readout of 57deg. while driving at varous speeds while it would drop down to 55deg. while I was idling. I'm guessing a recharge is in order although supposedly the previous owner had the (cooling unit-?) replaced at the end of last year and there hasn't been more than about 10k put on it since then. Although I can see the new parts I'm not the most mechanically inclined and am not sure exactly what was replaced considering I didn't see any receipts.

Thanks in advance for any responses-
Tim

[troy1]

I would say your a little low on R-134A your temp should be down in the upper 30's to low 40's

[sroney]

I have a 2000LS that has been a great car (125k miles now). However, last summer the gas mileage started to drop slightly. The on board computer had been saying the mileage was 24.5. And this was an average over 100,000 miles. (I had never reset the computer) So this was truly an "average" MPG.

I had the spark plugs changed at 115K, along with the wires, a fuel injector cleaning and fuel filter. Since then my mileage has steadily dropped to 24.1 on the on board computer.

This would not bother me much, but I just checked the mileage on one tank and got 19.3 MPG. I have noticed on long trips (Atlanta - Columbia SC) that I can get nowhere near the mileage I used to get.

I had the fuel pressure regulator changed per the recall that came out awhile back. Before that change the car had to be turned over for several seconds before it would start, and the engine didn't seem to have as much power. Once he regulator was changed, it started quicker, and the power seemed to be back. Now it is taking longer to start again, and the engine does not run as strong. I'm not sure if this is related to the mileage or not.

So where should I begin to look. I have always loved the mileage this car got, but now I can't help but think that something must be wrong. Any ideas??

[mighty_real]

113K miles on my '00 LS (3800) and I (still) get a faithful 23-24mpg. If it matters, this car has had a steady diet of Mobil1 (since first oil change at 6K miles) and premium fuel. Most recently I've been using Shell V-Power (premium fuel) and I find that morning cold starts are a lot easier. I feel that I've never skimped and I think that it's paying off now with continued good overall performance.

John

[57chevyragtop]

Well G! seems as though you have covered about everything in the tune up. Just a couple ot things come to mind, 1. Air filter condition. 2. throttlebody cleaning. Not much of a drop but could be a degradation of fuel quality which would be temporary the way fuel is being moved lately (formulation suspensions) That and the weather being hotter than normal as of late may have some effect. Tire pressures? Air conditioner on more often? Best I can think of...

[Stretch58]

Have a 2005 3.8, getting between 28-31MPG depending on how much 10% Ethanol I am forced to buy. When I drive up to Minnesota, all gas there has to have Ethanol in it. Came back again last Friday, A/C on all day, 100deg as I rolled into town, averaged 28+ mpg.

[57chevyragtop]

That seems to me a very good mileage considering the size the Impala. Plus it does not have the best profile for drag coefficient. There are so many variables in gas mileage ie: jack rabbit starts or just how many start/stops on a run to extra wt. carried like junk in trunk! I think most of us think we're doing more highway than we really are and therefor think our mileage is bad or something is wrong unreasonably. One can only adapt his or her driving habbits so much then you you hit the bottom line. If it's not enough then one has to decide on going to a smaller engined vehicle. As for me, I like the safety factor of a larger car and think the cost of operation is a price well paid.

[CT Tim]

I finally got a chance to go for a decent amount of nonstop highway driving (approx. 75 miles). The traffic was very light so I was able to maintain a constant speed of 65mph but I was rather dissapointed with my calculation of slightly over 22mpg.
I know people with various ford panther platform vehicles that pull a good 24-25mpg higway and they weigh approx. 800 pds. more.

[57chevyragtop]

Well that doesn't sound too good to me, 75 mi. is not a long trial but should be decent as long as the stop an go portion is less than 5%. mileage will drop quickly when you figure in town driving gets you 13-16 mpg...which seems to be about the avg for these Impalas. I know I stated in an earlier post I thought 50/50 city/highway would give around 23-24 but I am rethinking that from what I have been experiencing with my 3400 Imp. On my trips (2) 320 miles each 98% highway got me 34 MPG. I did not use steady speed in any way, 65-80 and yes 85 too! State Patrol had me on the gun but didn't come after me...whew! Now that would make the mileage factor moot for sure.

[CT Tim]

Yea, I try and keep it under 70mph considering CSP utilizes everything from planes to DOT trucks to perform radar in addition to their countless unmarked vehicles such as Impalas-rather ironic to be pulled over by one of them if the whole point was to measure the mpg in your own.
Now does anyone think I should invest any money in further researching the low mpg, or just accept it as the best this car can get?
Also, does anyone know if there was any signifigant change to the later model Impalas that would improve mileage considering I notice many people with newer models stating much better fuel economy.
Tim