M6 vs A4 highway mileage - Pontiac GTO Forum
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post #1 of 37 (permalink) Old 09-26-2004, 10:30 PM Thread Starter
 
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M6 vs A4 highway mileage

I am considering getting a '05 GTO with the automatic (or maybe a '04 if I decide I shouldn't wait on a LS2). I've noticed with the LS1 '04s the M6 mileage rating is 17/29 while the A4 is 16/21. I imagine the LS2 will be comparable.

Does anyone know why the automatic's highway mileage is so low? The LS1 in the Vette and F-bodies did not have such a drop in highway mileage when going from M6 to A4. The T/A's with M6s are 19/28 and the A4s are 18/26.

I've got a '88 GTA with the 5.7/A4 and a '01 T/A with the M6. Comparing the two, I know my next car will be an auto, but the GTOs low hwy #s are alarming considering what that engine does in the F-body.

Thanks,
Brent
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post #2 of 37 (permalink) Old 09-28-2004, 03:53 PM
 
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Not sure yet why the mileage is so different, but don't forget about the $1000 gas guzzler tax on the auto. It's like rubbing salt into the wound.
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post #3 of 37 (permalink) Old 09-28-2004, 06:27 PM
 
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I tried to find out why that was... Both the A4 and the 6 speed have the same final drive gear ratio. And the A4 has a 'lock up' torque converter once in 3rd.

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post #4 of 37 (permalink) Old 09-28-2004, 07:46 PM
 
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George, the 4L60E trans has an overdrive ratio of around .75:1. The six speed trans actually has two OD gears. Fourth gear is 1:1, fifth is around .75:1, and sixth gear is .5:1.
The final drive ratio for the auto trans car would be approx 2.60:1 and the manual would be 1.73:1. The F-bodys had the same setup, so I still don't know why the auto trans GTO suffers so much. Maybee someone will come up with an answer.

Brian
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post #5 of 37 (permalink) Old 09-28-2004, 10:15 PM
 
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Hey Brain... Your right... opps, heres the ratios, is this amount enough to make that much differance in MPG?

Even though is article is for the 2005 the ratios are the same as the 2004

http://www.newagegto.com/05GTO.html
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post #6 of 37 (permalink) Old 10-01-2004, 08:23 PM
 
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Quote:
Originally Posted by George8211
Hey Brain... Your right... opps, heres the ratios, is this amount enough to make that much differance in MPG?

Even though is article is for the 2005 the ratios are the same as the 2004

http://www.newagegto.com/05GTO.html

That's a 30% difference in gears which is enough to give that difference. Something else to look at is the range for highway driving of both cars. The number on the sticker is an average, but sometimes that range is more telling.
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post #7 of 37 (permalink) Old 10-11-2004, 09:34 PM
 
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what kind of mpg is everyone getting? i have 600+ miles and havent averaged over 15 mpg with half of my driving on the highway. i havent driven it hard and still no increase.
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post #8 of 37 (permalink) Old 10-12-2004, 08:17 AM
 
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Originally Posted by rickglow
what kind of mpg is everyone getting? i have 600+ miles and havent averaged over 15 mpg with half of my driving on the highway. i havent driven it hard and still no increase.

16-18 mpg by the tell tale little gage. I drive through the city on 'backroads' 25-45 speed limit (I'm usually 5-10 over the limit). I haven't had a chance to go on a long distance trip with it to see what it will get on the Interstate yet though...
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post #9 of 37 (permalink) Old 10-12-2004, 11:58 AM
 
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Mileage

I have taken two extended highway trips with my GTO so far, with approximately 800 highway miles. Average MPG on those trips is 20, according to the digital gauge. I have yet to compare to amke sure that readout is accurate.
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post #10 of 37 (permalink) Old 10-12-2004, 06:55 PM
 
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I've also taken a couple of trips in my M6. Went to S Georgia last month... approx 450 miles one way and averaged 25mpg according to the digital thingy. That was doing 65-85mph pretty much the whole way. I think my average speed for the trip was 76. In town, I'm averaging 17mpg.
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