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Chevrolet Impala Real World MPG

123 messages,  Last post on Apr 21, 2011 at 11:06 PM

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

Messages Page 9 of 13

#74 of 123 Weekend experience by nosirrahg

Oct 29, 2007 (3:13 pm)

We rented a 2007 (or 2008, I actually didn't notice) 3.5l Impala for a long weekend trip to Kansas City recently. I put over 1,000 miles on the car, and had the compressor running pretty much the entire time (AC on the drive up, and defroster running all the way back), and averaged 29 MPG. The DIC showed closer to 31 MPG, but when I got back and tallied up the receipts, it came out just over 29. Still not bad considering there were four of us plus luggage in the car most of the time, and I was driving 70+ MPH for the bulk of the trip.
 
My only complaint about the car was the lack of a center armrest (and more importantly, cup holders) for the rear seat passengers; otherwise it was a great Interstate cruiser.

#75 of 123 '08 Impala 3.5 purchase being considered by dave8697

Nov 06, 2007 (7:10 pm)

I read a lot of differences in mileage reports. There are a few key factors and a few medium factors in mileage. Key ones are how much braking, how much accelerating, and how much % of time just cruising in high gear. Medium factors are correct tire pressure, clean air filter and how fast acceleration is. Other factors are if you are a drafter or a draftee, wheel alignment, tire type, engine tune, flatness of terrain and how fast you go on the interstate. Aerodynamic Drag is a function of velocity squared. At 70 mph, relative drag effect is 4900. At 80 mph, drag effect is 6400. 14% more speed created 31% more drag force on vehicle. Luckily, mileage doesn't drop 31% when you speed up to 80 mph due to high powered engines and well designed transmissions in cars. Even wind can effect mileage. If I drive into the wind both ways on my 47 mile commute, it will reduce my mileage. I Think The best way to compare mileage is to take a 200 mile trip at no more than 75 mph and report that number only. Any city number or number for a short stop and go commute is greatly affected by the factors listed.
 
I drive my son to college in his V6 Mustang too often and it's an 85 mile trip of which only 30 miles is on an interstate. I counted the lights and discovered there were 60 of them. Thats a stop at an average of every 1.4 miles. The car gets 29 mpg on these trips. I thought it was highway driving until I counted all the lights. It gets 29-30 driving the 47 mile commute to work. Even With heavy stop and go rush hour traffic averaged in, it gets 27-28. The stop and go driving is 20% of the trip distance but adds 20 minutes to the time to get there or back. I do not know the true trip mileage for the car, but don't expect more than 31.
 
I see a special price on an '08 Impala locally and the opportunity won't come around again. The LS model with a 3.5 liter V6 seems to be capable of low 30's on a trip according to some posters here. My work commute usually gets me 28 mpg for my 3800 Buick and 29 mpg for the 3.8 L Mustang. Based on this I think the Impala could get 29-30 commuting. The Impala is a lighter, smaller, lesser powered, smaller engined car than my Buick.
 
When I looked into a Cobalt, I was expecting about 32-33 for my commute but didn't get one. This Impala opportunity is at a better price than the Cobalt price was at the time. Can anyone say that the Impala 3.5 is not capable of better mileage for me than my pair of 3.8 liter cars (28 and 29)?

#76 of 123 Re: '08 Impala 3.5 purchase being considered [dave8697] by nosirrahg

Nov 06, 2007 (8:54 pm)

Replying to: dave8697 (Nov 06, 2007 7:10 pm)
I've got a 2000 Impala with the 3.8, and my highway mileage runs comparable to your own experience. While I don't own a current issue Impala, I've rented one two or three times. I was a little disappointed with the mileage on this most recent trip (almost all highway, but didn't average over 30 MPG as hoped). However, a couple of years ago I rented a 2006 model (3.5l), and driving from southern Illinois to Terre Haute, IN at the posted 65 MPH speed limit (and with the AC on), we averaged at or just over 36 MPG (both on the DIC and manually calculated). I posted the precise results on Edmunds somewhere, possibly in this same forum (though I don't remember).
 
If my commute involved a lot of highway miles, I wouldn't hesitate to buy a 3.5l Impala. On the worst of days it'll equal the best mileage you're getting with the 3.8l cars, and on it's best days it'll do much better.

#77 of 123 2008 LTZ gas mileage by norbnancy

Nov 10, 2007 (7:50 pm)

My 2008 LTZ has 4900 miles and produces 25.9573 MPG since new. The worst was 20.6 MPG, the best 30.1 MPG. I think it may get better when and if it loosens up. It still feels tight- doesn't seem to roll freely. I am basically satisfied with the fuel mileage. The car otherwise, is perfect. My 30.1 MPG stint was about 240 miles on I-75 in Michigan at 65 to 70 MPH.

#78 of 123 2006 Impala SS by quietpro

Nov 28, 2007 (7:47 am)

I just finished a trip for the Thanksgiving holiday and set a new record for gas mileage with my SS. I would like to look at a topographical map to confirm my suspicions but I believe I'm gettng better mileage based on a overall down slope on the trip. I fill up at the same gas stations to and from my destination so I can gauge the difference in each direction of travel.
 
Here are my results:
 
Northbound legs
25.34 mpg/54.1 mph and 27.37 mpg/67.1 mph
 
Southbound legs
29.33 mpg/69.7 mph22 and 22 mpg/64.1 mph
 
I cheated a little on the 29.33 mpg leg by resetting the car's trip computer after I accelerated to cruising speed. However, the car's indicated fuel mileage was actually slightly lower at 27.7 mpg. I attribute part of this disparity to possibly filling the tank a little more prior to this leg. But, even if I added an extra half gallon at the end, which I know I couldn't have fit, the mileage would have only dropped to 28.7 mpg.
 
The leg listed first is through fairly level terrain through SC, NC, and VA on I-26 and I-77.
 
The leg listed second is through the mountains of VA and WV on I-77.
 
These results are consistent with other trips I've taken over the same route. This is why I believe I may be seeing an overall result of uphill vs. downhill mileage over the course of the leg. It's pretty interesting, though, as my mileage has continued to improve as the car wears in. I now have about 29.5K on the odometer. Regardless, getting over 25 mpg, UPHILL, with a V-8 engine producing over 300 HP is damned impressive. One last note, I achieved these latest results on 87 octane...so maybe I was producing a little less than 300 HP. The lower octane doesn't seem to affect fuel economy so I plan to use it for the road trips from now on.

#79 of 123 Re: 2006 Impala SS [quietpro] by pulgo

Nov 28, 2007 (9:12 am)

Replying to: quietpro (Nov 28, 2007 7:47 am)
You say:
"I cheated a little on the 29.33 mpg leg by resetting the car's trip computer after I accelerated to cruising speed. However, the car's indicated fuel mileage was actually slightly lower at 27.7 mpg. I attribute part of this disparity to possibly filling the tank a little more prior to this leg. But, even if I added an extra half gallon at the end, which I know I couldn't have fit, the mileage would have only dropped to 28.7 mpg. "
 
To calculate MPG one should simply divide the miles traveled by the amount of gallons on the receipt after the fill up.
 
Using the computer won't give meaningful numbers.

#80 of 123 Re: 2006 Impala SS [pulgo] by quietpro

Nov 28, 2007 (10:10 am)

Replying to: pulgo (Nov 28, 2007 9:12 am)
The computer on the 06+ Impalas is actually pretty accurate. While I never get the same number when calculating mileage manually, it's usually within .5 mpg.
 
You are assuming too much when you state that all that is required to calculate mileage is to divide the miles by gallons at fill up. Filling a fuel tank isn't an exact science since the cutoffs at various pumps will vary. Also, most people usually pump to an even dollar amount. You can never be certain you have filled your tank to the exact same posiiton everytime. That's why I go with averages to compensate for those variances. As I stated, I believe I pumped a little more fuel into the tank before that last leg than I did at the conclusion. That would give the impression that I achieved better fuel mileage than if I managed to squeeze an extra half gallon or so into the tank. I acknowledged that in the post (accounting for mileage if I were to calculate based on an extra half gallon of fuel).

#81 of 123 Re: 2006 Impala SS [quietpro] by pulgo

Nov 28, 2007 (1:27 pm)

Replying to: quietpro (Nov 28, 2007 10:10 am)
To eliminate all those variances I calculate my mileage averaging the last 10 fill ups. This would be for approx. 4k miles.
 
Since I always drive the same route the only major changes happen when the colder (not really very cold) season starts in November or when it starts to warm up in March.
 
Here in Vancouver, BC, the lowest temperatures we get are around 20 degrees F and don't stay for long periods of time.
 
By the way, I own a 2007 Sentra that is in for service today and the loaner I got is a 2007 Impala. What a nice car! If I believe the computer I am getting 32 MPG on my commute and that would be awesome!

#82 of 123 Re: 2006 Impala SS [pulgo] by quietpro

Nov 28, 2007 (2:26 pm)

Replying to: pulgo (Nov 28, 2007 1:27 pm)
I average as much as possible but my commute often involves traffic jams which aren't uniform. The best I can do is average over the last few trips which WERE consistent even though temperature and speed will vary slightly.
 
32 mpg in a V-6 Impala is very feasible...especially with the 3.5L engine.

#83 of 123 3.5 V6 vs 2.4l 08 Malibu by zeeboy

Apr 19, 2008 (10:39 am)

Seems the 3.5 V6 is nearly as fuel efficient as the new Malibu in real world numbers.

Messages Page 9 of 13

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