| [GMCnet] Interesting mileage comparison. A no tech post. [message #367023] |
Sun, 03 October 2021 02:16  |
BobDunahugh
Messages: 2465
Registered: October 2010
Location: Cedar Rapids, IA
Karma: 11
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Both GMCs are very well maintained. Didn't really want to post this. But I find this too fascinating. Sorry.
Got this 76 GMC for our daughter last May. Our 78 GMC Royale Heavy
76 -455 10,500 LBS X 78 -403 12,000LBS
Towing a Tracker 2,900LBS. 4 down. X Towing a Chavy Uplander Van 5,350 LBS. On a Dolly. Total GVW 13,400 LBS X Total GVW 17,350 LBS.
Engine milage 18,000 Engine mileage 38,000
Howell EFI EBL Howell EFI EBL
No cold air induction in grill X Cold air induction in grill
Synthetic Engine oil X Standard mineral oil
E-85 gas E-85 gas
Headers X Stock exhaust manifolds
3-inch exhaust system X 2.5- inch stock exhaust system
3:42 Final Drive. X 3:70 Final Drive
One A/C unit on roof ( Wind Drag. ) X Two A/C units on roof. ( Wind Drag. )
Trip speed. Mostly 65 to 70 Trip speed. Mostly 65 to 70
Larger outside rear-view mirrors Same larger rear-view mirrors
Lt 225/75 R 16s LT 225/75 R 16s
Tire pressures at 60 PSI Tire pressures at 60 PSI
Aluminum 16 rims Aluminum 16 rim
Cruise control used Cruise control used
Center axle disc brakes Linz Center axle disc brakes Harris
8.9 MPG X 9.3 MPG.
No real point to be made. Just interesting. the X makes note. That of those differences. To me. Seeing that the 403- 3:70 FD. Got better MPG. And pulling just under 4,000 LBS more. Then the 455- 3:42.
It's been noted many times. That the 403s love RPMs. I pull my 24 ft enclosed race trailer a lot. With a GVW of around 24,000 LBS. That's like pulling another complete GMC along as a trailer. People on this site. Have seen that trailer at some GMCMI events. With that trailer. I generally keep the RPMs above 3,000. Plus. Those higher RPMs help keep trans temps lower. I rebuilt that trans myself in 2004. Has over 100,000 miles on it. All is still well.
Bob Dunahugh
78 Royale since 2003
4 real COPO Yenkos
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| [GMCnet] Re: Interesting mileage comparison. A no tech post. [message #367026 is a reply to message #367024] |
Sun, 03 October 2021 13:40  |
James Hupy
Messages: 6806
Registered: May 2010
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Before we had ethanol laced gasoline, my coach, a heavy 1978 Royale with a
403 and 3:07 final drive would achieve a steady 11-12 mpg at a steady pace
of 60 or so. But, it wouldn't pull the hat off your head. So, I set about
doing some "technical enhancements", namely a 3:70 final drive, Doug
Thorley plated headers, carb enhancements as well as ignition recurve to
take care of the lean mixtures that the headers caused.
It then would run like a scalded dog, climb grades with any coach, and
still got 10-11 miles per gallon at 65-70 mph on regular non ethanol fuel.
Then came the ethanol laced fuel. Sad day in my opinion. My mileage
dropped to 8-9 mpg. No other changes.
When we crossed Canada coast to coast, they still had non-ethanol fuel
and my mileage on that trip went back to 11- 12 mpg.
So, don't blow no smoke at me and tell me that ethanol laced fuel is
good for me. Corn farmers get a heck of a subsidy for growing corn for
alcohol. Them, it is a benefit. You and me? Not so much. Rant off!
Stay well out there. Judy got her 3rd Covid shot yesterday. No ill
effects noted.
Jim Hupy (Double J Royale Express)
Salem, Oregon
On Sun, Oct 3, 2021, 10:41 AM Dave King wrote:
> Bob, I think I note that the fuel used in both vehicles is E85. Is that
> correct ? If correct why E 85 ?
> --
> DAVE KING
> lurker, wannabe
> Toronto, Ontario, Canada
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| [GMCnet] Re: Interesting mileage comparison. A no tech post. [message #367035 is a reply to message #367024] |
Sun, 03 October 2021 21:49 |
BobDunahugh
Messages: 2465
Registered: October 2010
Location: Cedar Rapids, IA
Karma: 11
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________________________________
From: Dave King
Sent: Sunday, October 3, 2021 12:41 PM
To: gmclist@list.gmcnet.org
Subject: [GMCnet] Re: Interesting mileage comparison. A no tech post.
Bob, I think I note that the fuel used in both vehicles is E85. Is that correct ? If correct why E 85 ?
--
DAVE KING
lurker, wannabe
Toronto, Ontario, Canada
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