Chevrolet Impala Real World MPG

hawkman · February 2009

I just traded my 2007 LT for a 2009 LT because of the traction and ABS. This may be too early to tell but my gas mileage seems have decreased from 24 with the 2007 to 20 (2009) in normal driving with the same engine size.

This could be due to 2 main factors 1) This is a new car with less than 1500 miles on it presently 2) I am driving in the winter vrs the summer. I'll be taking on a 1200 mile trip this weekend to check the highway mpg.

I would like to hear from drivers with the 2009 to compare and see what mpg they are getting. I miss my 24 (although it was in the summer).

I know cars get worse mileage in the winter for a variety of reasons, but does the car get better meileage as it gets older and more broken in? :confuse:

rvoth · February 2009

Just a friendly reminder that you shouldn't just lock the car on cruise and let it go.

The engine should have varying speeds, so the engine parts can heat up and break in under normal hwy speed and then cool at slower at slower hwy. This should be done with the time intervals 15 min normal and 15 min at slower speed. It will greatly help the fuel mileage and overall performance of the life of the engine.

My father just purchased a SS impala , it went on a 3000 km trip and the fuel mileage was 24-27 mpg. They just went on a 500 km trip on flat land and the mileage went up to 32 mpg. This improvement is probable due to the previous trip through the mountain ,varying the speeds and allowing the V-8 engine to break in.

Still the fuel mileage hasn't reach the rated 37 mpg but it only has 4000 km and is being driven in winter. Even with the fuel management system that works very well GM's mpg for the v-8 is hard to reach.

saxe10595 · February 2009

2008 LT 50th edition. Now I have about 10k mileage. Computer shows average mileage to be 21.4. I get 26-27 on highway and 18-20 in the city. It has 18" wheels could this be cause of low mileage ? as GM claims anywhere upto 29 MPG.

quietpro · February 2009

Lots of things can cause mileage to vary. The EPA estimates are achieved at 60 mph I believe. Try setting your cruise at reasonable speed, reset the mpg average, and see what you get. It won't take a long trip to get a close approximation of mileage. Try it in both directions to help rule out any slope in the trip or head wind.
I can average above the EPA estimate at 65 mph with my SS (5.3L V-8).

BTW, the wheel size shouldn't have a great effect in highway mileage. The biggest impact of wheel size would be in city mileage where the added weight would effect fuel consumption. The effect while cruising would be minimized.

hawkman · March 2009

" Using the computer won't give meaningful numbers. "

I've found this to be true on a 2009 Impala LS. It says I got 25.3 mpg, but upon checking (miles vrs gas used) it comes out to 22.9. That too me is a huge difference. This is the second fill up in a row I have tested it and they both came back the same - way off.

quietpro · March 2009

When comparing mileage (actual vs. computer), keep in mind that you are attempting to fill the tank to the EXACT same level for an accurate comparison. If you stop the pump at an even dollar (like most people), you may be topping off with varying amounts each time. If you stop when the pump cuts off, that will vary by the fuel nozzle and how far it is inserted into the filler tube. Even 1/4 gallon will skew the results a great deal. Add to that the calibration of the pump at the gas station you're using. While they are regulated, there are still many cases where pumps are intentionally set to deliver less fuel than is indicated. Even different pumps at the same gas station can skew your results.

I have tracked my mileage since I bought my car over three years ago. I am always within a 1 or 2 mpg from the indicated amount...but less than 1 mpg difference 95% of the time. The computer in my car is extremely accurate and given the variances that I am forced to deal with, it may be more accurate than I am capable of being.

ryster · March 2009

The Driver Information Center ("DIC") in my '06 Impala 2LT is very accurate. Usually no more than 1mpg off from what I calculate manually. In fact, it is accurate enough that I can look at the calculated miles to empty before filling up and estimate how much gas the car will take (for example, if the DIC says the range is 66 miles, and the DIC shows economy of 22mpg, the car will take 14 gallons.) It is usually right on and fills to the point where gas almost overflows.

I have found when filling up that regardless of what gas station I use, the pump shuts off about 2 gallons early. Meaning, I can usually put 2 more gallons in after the pump first shuts off.

txguy · April 2009

My 01 Imp LS mileage has dropped from the early 28-32 mpg to 22-24 mpg now at 255,000 miles. Otherwise the car looks and drives great. I have been completely satisfied with this car. The only non routine work on this car has been replacing cat twice, one wheel sensor, one coolant level sensor, the radiator and then the motor mounts at 225,000 miles. The fuel gauge hasn't worked since 110,000 miles, but I got used to tracking the miles on the trip odometer. I use Mobil 1 at 3,000-5,000 change intervals, do the transmission flushes and fuel system cleaners as recommended and that's about it. Oh and the last set of Michelins on this car went 114,000 miles. GM does build good cars!

highmiler650 · April 2009

How about changing the fuel injectors? This might restore some of the lost MPG.

txguy · April 2009

I never even considered changing out the injectors. Good idea. I keep thinking I am going to trade it in, but then I haven't found anything I like better.. and of course, this one is paid for. Oh and I might change out the plugs too. This is only the second set for the car. :-) They are such a pain to change.

highmiler650 · April 2009

Although many cars have spark plugs that may last up to 100k miles I believe in changing them every 3 years or 60k miles at most.

The reason is that although they might survive much longer periods working as intended, they are notoriously difficult to remove after many years.

Even when installed properly with a bit of anti seize compound they are a pain to remove without causing damage.

I always get new plugs at around $ 2 per plug (platinum) so the investment is really not much.

Lastly, your car is paid for and anything requiring fixing is going to be much cheaper than 3 to 5 years of monthly payments, especially in these tough times.

gar_fanatic · April 2009

Wow, where are you finding platinum plugs for only $2.00 per plug?!?! The cheapest I can find Delco ones is $6.00 per plug. I won't put anything else in my 'Pala.

At 255k, have you had to replace your upper intake manifold yet?

txguy · April 2009

replaced intake manifold at 50K or so. I also use only plugs that the car is designed around, Delco.

highmiler650 · April 2009

Schucks usually has them discounted to this price on one of their flyers (state of Washington, Bellingham area).

highmiler650 · April 2009

The car will run fine on any brand as long as they are equivalent to the Delco you mention (Bosch, Champion or any other well known brand)

mobilejo · December 2010

I had a 2002 Impala that got great mileage 22-25 city and 30-32 highway, so I bought a new 2009 last year. My mileage has been terrible compared to the 2002 impala. Now I get 15-18 city and 20-22 highway, with 24 my best mileage ever on this car.

I was really disappointed in the mileage but the car is great and I love everything about it except the mileage.

sparky60 · February 2011

sparky60 · February 2011

I am wondering if anybody is having problems with gas mileage for their 2010 Impala. I checked my mileage today. Am getting 13.8 mpg. very dissapointing. I took the car in a few days ago to my Chevy dealer. They scanned everything and said all is to factory specifications.

deminin · February 2011

I get at least 21 MPG around town, and the highway mileage varies between 25 to 28, depending upon whether I am using the AC, and/or speeding. At 65 with no AC, I can hit 28. Cruising at 75 drops the mileage to 26, and anything over 80 cuts the mileage back to 25, or less. The LTZ suspension makes a great long distance higher speed road car....firm, but not harsh.

backy · April 2011

I got to drive a 2011 Impala rental on a 270 mile trip today, thanks to Delta canceling my flight home due to the wind being too strong for their little puddlejumper jet. Car had 12k miles on it. Almost all the trip was interstate at between 65-68 mph, with cruise on. Some city streets at the beginning and end, and two stops along the way. Had high winds during the trip, but mostly cross-winds. Temperature between 32-40 F. I was quite impressed with the fuel economy for a large car with a big V6: 33.9 mpg. That's in the same neighborhood as some smaller 4-cylinder cars I've driven on the highway.

hersbird · April 2011

I got 21.3 on the last tank all city and the computer and the hand calculated came out with in .2 of each other. During a highway trip tonight at about 70 over 50 miles I averaged 28 according to the computer. If I backed down to 60 the cylinder deactivation would hold speed and it went up to 33 mpg on the computer on a flat steady section. This trip tonight was with new wheels and tires that have thrown off the speedometer by 4-5 mph low. So would that mean I'm actually getting about 5% better then indicated? That means 29.4 average highway.
This is on a 2007 with the 3.9 with new 235/50/18 tires in place of the factory 16's.

Chevrolet Impala Real World MPG

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