eagle1328
colorado
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Joined: 03/19/2012
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Considering up-dating from a 1997 7.4 to a 8.1. Many reasons for not considering a diesel. The 97 8.1 gets 14 highway 9 loaded. When I hit the Colorado mt. passes 10,000 + feet towing 9000# the mpg goes to 7/8. thannks
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NewsW
US
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Joined: 02/06/2012
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Skip diesels for now... wait until the SHTF settle down in 5 years.
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donn0128
Pronounced Ore-gun
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Joined: 04/21/2005
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All you need to do is search the RV forums. The 8.1L will get you maybe 8 towing and maybe 12 empty. Definitely worse than what you are saying now.
Donn,Lorri,Max (The Rescued Lab)
Resident Know It All 
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Nomadac
Columbus, IN
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Joined: 11/22/2004
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I have a 2001 2500 Suburban 2wd with 8.1L 4:10 axle ratio and got 9+ mpg towing our 32' Avion that weighed 7600# towing at 70 mph. The city/highway was 12/14+ mpg.
Arnie
2003 Travel Supreme MH
38KSO1 Cummins ISC 350HP
2004 Honda Pilot w/SMI Air Force One Brake Sys.
1963 Pontiac Grand Prix 20' Enclosed Car Trailer
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rvten
Crossville,TN
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Joined: 11/30/2000
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Did not see this was TV.
Tom & Bonnie
Crossville, TN.
Aspect 29H 2008 Type C
Ford Flex SEL 2010
There is no B+
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Devocamper
West Haven CT
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Joined: 02/15/2004
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We had a GMC with the 8.1 allison combo, great TV . towed our TT and then our 5th wheel with no problems but only got 5-8 mpg towing and maybe 10-12 empty . If you dont mind feeding it this combo is a great TV. The other problem is range if it is in a short bed it only has a 26 gal fuel tank so you make many stops for fuel on a long trip. The GMC 2500HD ext cab short bed served us well but the 3500HD dual rear wheel duramax allison is better for what we are now towing .
08 NU-WA Hitchhiker Discover America 339 RSB
07 Chevy 3500HD LT1 EXT Cab LB DRW D/A
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BenK
SF BayArea
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Joined: 04/18/2002
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My GMT400 7.4L/4.1's with LT265/75R16E's gets 10MPG city, 12-15MPG highway
and 7-8MPG towing heavy from sea level to Lake Tahoe (+8K passes)
I drive HARD
-Ben Picture of my rig
1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
Sold the boat (looking for another): Trophy with twin 150's...
51 cylinders in household, what's yours?...
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Ford Man
Tennessee
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Joined: 04/30/2005
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I know a guy that had a 8.1 liter in a 2500 GMC and towed about 12,000 lbs. 5th wheel and he told me that he averaged 6 MPG here on the East Coast.
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Gale Hawkins
Murray, KY
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Joined: 07/22/2007
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454 Vortec (7.4L) and 8.1L should be about equal MPG.
Fully loaded MPG should be in the 5-10 MPH depending on many factors.
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nremtp143
Georgia
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Joined: 08/29/2010
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I have an '01 3500 CC LB 4x4 with the 8.1L/Allison combo, and it gets 10-12 empty and 6-7 while towing a high profile 40ft 5er. Absolutely love the truck, just wish it would tow my new 5er better. It can pull it, it just downshifts a lot and revs very high.
2012 Sandpiper 365SAQ, Goodyear G614s, TST TPMS
2010 F350 DRW 6.4L 4x4, Edge CTS, B&W Companion, Viair 10007 air system, Firestone Ride-Rites,Flo-Pro cold air pipe
2001 Excursion Limited 7.3L 4x4, V/B Springs
2001 Silverado 3500 DRW CCLB 8.1L/Allison 4x4
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