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Old 08-07-2016, 09:42 PM   #81
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My olds 88 would eat injection pumps I finally got rid of it when I had problems with the top end. Never got any help from GM.
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Old 08-08-2016, 11:25 AM   #82
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Question to the group....
What is a good speed/rpm to maintain while cruising down the Interstate to get the best gas mileage??? I have seen a lot of various answers on this topic. I have a 2012 Ram 3500 that has been stripped of all the EGR stuff and updated with a tuned chip with 5 programs. I pull a 2013 Forrest River Viper XLR Toy Hauler. I have tried every speed from 60 - 70 and can not find a good setting that produces decent MPG's.
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Old 08-08-2016, 11:38 AM   #83
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Question to the group....
What is a good speed/rpm to maintain while cruising down the Interstate to get the best gas mileage??? I have seen a lot of various answers on this topic. I have a 2012 Ram 3500 that has been stripped of all the EGR stuff and updated with a tuned chip with 5 programs. I pull a 2013 Forrest River Viper XLR Toy Hauler. I have tried every speed from 60 - 70 and can not find a good setting that produces decent MPG's.
Now that's a can of worms!!!! It just depends on your setup. For my duramax, it's anything under 1900 rpm. I probably do best at 65 to 68 mph, but I always run 70 so I don't have to pass/be passed by a lot of semis. Not a whole lot of difference in mpg. I usually avg 11mpg towing over a long trip.The 'how slow can I go' group will say to run 55. If you have already tried a speed range of 60 to 70 I'd say you've got what the you've got as far as mpg.
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Old 08-08-2016, 01:14 PM   #84
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I have a Silverado 3500 diesel and my best mpg is at 63mph. I get passed a lot


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Old 08-08-2016, 01:17 PM   #85
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my input probably doesn't matter much for your situation because I'm using a gasoline TV. However most of our travels happen in Utah, highway speeds are 80mph in most places so semis blow bye me all the time, I stick to 60-65. Anything more I get down around 10mpg
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Old 08-08-2016, 02:49 PM   #86
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My brother had an early 80s vintage Isuzu diesel pickup. I'd wager a bigger POS than those Olds diesels?


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Old 08-08-2016, 03:44 PM   #87
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Question to the group....
What is a good speed/rpm to maintain while cruising down the Interstate to get the best gas mileage??? I have seen a lot of various answers on this topic. I have a 2012 Ram 3500 that has been stripped of all the EGR stuff and updated with a tuned chip with 5 programs. I pull a 2013 Forrest River Viper XLR Toy Hauler. I have tried every speed from 60 - 70 and can not find a good setting that produces decent MPG's.
Lots of variables on this, but my particular truck / trailer seems the happiest at about 70, which is about 1600 RPM. It will climb most grades at that too, save for the longer and steepest grades.

MPG... I have seen between 11 and 13 from this rig driving at 70 with the cruise set.
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Old 08-09-2016, 11:50 AM   #88
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Just to get the facts, not debate politics: do you have a source for the claim that the Prius and other hybrid and batter electric vehicles produce more carbon over their whole lifecycle?

Here's a recent report from the Union of Concerned Scientists: Life Cycle Electric Vehicle Emissions (2015) | Union of Concerned Scientists.

Summary: "the Union of Concerned Scientists undertook a comprehensive, two-year review of the climate emissions from vehicle production, operation, and disposal. We found that battery electric cars generate half the emissions of the average comparable gasoline car, even when pollution from battery manufacturing is accounted for."

Of course, no one makes a Prius or Volt, etc. that can come close to towing a TT! So, back to topic: pulling uphill in cruise. Last month, I got nervous going 55 near the top of Willamette Pass in Oregon as I saw the tranny temp going well into the 200's. I pulled over at a viewpoint and let the engine cool a bit. No warning lights or anything, just feeling that we were pushing our 2010 Avalanche 1500 (gas) too hard. Was I too conservative? I saw a tranny temp discussion here a while back but it was outdated. Any wisdom?
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Old 08-09-2016, 11:56 AM   #89
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Upgrade to an external trans cooler.


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Old 08-09-2016, 12:16 PM   #90
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Best economy from 60-70 mph? Physics pretty much demands that to be 60mph, especially with a high top-flat rear door toyhauler. Assuming the truck is in the highest gear at 60 mph, you always will get the best mpg when the car-truck-train-spaceship-whatever is in the highest gear with the torque converter locked up and going the lowest speed possible to maintain that condition. It's all about aerodynamic drag at highway speed.
More on topic, I had a 2005 Duramax that seemed more then willing to try and self destruct on big grades towing big loads. Would it have? I don't know, but seeing the EGT and transmission temp climbing like that while passing semis made me back off before finding out. They should have EGT gauges standard on every diesel from the factory. It also can help with fuel economy because as that thing climbs the economy goes off a cliff.
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Old 08-09-2016, 01:53 PM   #91
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Correct me if I am wrong, but in the owners manual for my 2008 it tells you NOTE to use cruise control if you are in town haul mode
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Old 08-09-2016, 02:05 PM   #92
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Correct me if I am wrong, but in the owners manual for my 2008 it tells you NOTE to use cruise control if you are in town haul mode


You absolutely use cruise control and tow/haul mode together with the Allison. GM calls it Cruise Grade Braking. It's a feature that helps maintain downhill speed. Works like a charm in my 2008.


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Old 08-09-2016, 02:06 PM   #93
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You absolutely use cruise control and tow/haul mode together with the Allison. GM calls it Cruise Grade Braking. It's a feature that helps maintain downhill speed. Works like a charm in my 2008.


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Cut and paste from the owners manual:

Cruise Grade Braking (Allison Transmission[emoji768] or Hydra-Matic[emoji768] 6-Speed Automatic Transmission)
Cruise Grade Braking assists when driving on a downhill grade. It maintains vehicle speed by automatically implementing a shift schedule that uses the engine and the transmission to slow the vehicle. Cruise Grade Braking operates while Cruise Control is engaged in Tow/Haul mode to assist in maintaining vehicle speed under loaded vehicle conditions. It utilizes vehicle acceleration and deviation from desired speed to determine the correct gear for the operating condition.
If vehicle speed is above the desired speed the transmission will downshift to slow the vehicle. If vehicle speed is near or below desired speed the trans will upshift, allowing vehicle speed to increase.
While in the Range Select Mode (RSM) mode, cruise grade braking is not available.
See Automatic Transmission Operation on page 2-28.


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Old 08-09-2016, 03:46 PM   #94
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I recently pulled our 5th wheel from flat Illinois to Gatlinburg, TN... the truck never had an issue pulling any grades with the cruise on (I did lock it in 5th gear in the hills). Downhill with cruise on and exhaust brake in the auto setting was super nice too.... the tranny will grade brake and the truck will vary the amount of closure on the turbo to maintain the set speed. Trans never exceeded 180, oil never exceeded 206, coolant never exceeded 200. I haven't added an EGT probe in the manifold yet, but post turbo EGTS didn't really increase much at all over the cruising temps.
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Old 08-10-2016, 10:59 PM   #95
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For my experience. The slower you go the better fuel mileage you'll get. Wind resistance is a mpg killer. And mpg increases exponentially as speed increases. For my truck, a 6.7 cummins, RAM with 3.42 axle, I keep it above 1500 RPM. 55 mph would be ideal as far as mpg goes but I'd get run over on the interstates. You pay dearly for speed when you are pulling a parachute. ha.
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Old 08-11-2016, 08:57 AM   #96
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The EPA being involved with is is a travesty. They shouldn't meddle in such affairs. I have the JGC EcoDiesel and easily get 25-28 mpg but if you get the same vehicle in Australia you are flirting with 50 mpg. So I ask you, is it better to get 25 mpg and save 10% on emissions or get 50 mpg? You would think that you are doing more for the environment by doubling the mileage, therefore using less fuel overall.

The Prius which everyone raves about is another scam as it's lifetime carbon footprint, from manufacture thru disposal is almost triple that of a Chevy Malibu with a six cylinder.

To think they have brainwashed these people into thinking they're helping the environment but in truth they're actually hurting it.
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