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Chevrolet Impala Real World MPG

117 messages,  Last post on Apr 15, 2009 at 11:28 AM

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What is this discussion about? Chevrolet Impala, Fuel Efficiency (MPG), Sedan

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#104 of 117 Re: Had a 2007, now a 2009 Impala LT [hawkman] by rvoth Feb 12, 2009 (9:57 am)
Replying to: hawkman (Feb 11, 2009 7:12 am) 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.
#105 of 117 mileage by saxe10595 Feb 28, 2009 (4:57 am)
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. Replies to this message: quietpro (Feb 28, 2009 7:18 am)
#106 of 117 Re: mileage [saxe10595] by quietpro Feb 28, 2009 (7:18 am)
Replying to: saxe10595 (Feb 28, 2009 4:57 am) 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.
#107 of 117 Re: 2006 Impala SS [pulgo] by hawkman Mar 28, 2009 (2:28 pm)
Replying to: pulgo (Nov 28, 2007 8:12 am) " 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. Replies to this message: quietpro (Mar 29, 2009 7:08 am) ryster (Mar 29, 2009 10:11 am)
#108 of 117 Re: 2006 Impala SS [hawkman] by quietpro Mar 29, 2009 (7:08 am)
Replying to: hawkman (Mar 28, 2009 2:28 pm) 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.
#109 of 117 Re: 2006 Impala SS [hawkman] by ryster Mar 29, 2009 (10:11 am)
Replying to: hawkman (Mar 28, 2009 2:28 pm) 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.
#110 of 117 '01 IMP LS 3.8 255,000 miles 22-24mpg by txguy Apr 14, 2009 (10:41 am)
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! Replies to this message: highmiler650 (Apr 14, 2009 10:54 am) txguy (Apr 14, 2009 10:59 am) highmiler650 (Apr 15, 2009 7:14 am)
#111 of 117 Re: '01 IMP LS 3.8 255,000 miles 22-24mpg [txguy] by highmiler650 Apr 14, 2009 (10:54 am)
Replying to: txguy (Apr 14, 2009 10:41 am) How about changing the fuel injectors? This might restore some of the lost MPG. Replies to this message: txguy (Apr 14, 2009 10:59 am) highmiler650 (Apr 15, 2009 7:14 am)
#112 of 117 Re: '01 IMP LS 3.8 255,000 miles 22-24mpg [highmiler650] by txguy Apr 14, 2009 (10:59 am)
Replying to: highmiler650 (Apr 14, 2009 10:54 am) 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. Replies to this message: highmiler650 (Apr 15, 2009 7:14 am)
#113 of 117 Re: '01 IMP LS 3.8 255,000 miles 22-24mpg [txguy] by highmiler650 Apr 15, 2009 (7:14 am)
Replying to: txguy (Apr 14, 2009 10:59 am) 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.

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