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Old 11-24-2017, 04:50 PM   #15
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I don't think the mpg difference is as much as some think it is.
I'll weigh in at 5 MPG, have never hit 6. It weighs 47,000 plus towing 7,000 = 54,000 total.
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Old 11-24-2017, 04:58 PM   #16
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I'll weigh in at 5 MPG, have never hit 6. It weighs 47,000 plus towing 7,000 = 54,000 total.

5.5-6.5 on our ISX15 with 600hp. 45,000+ Jeep

Been getting better mileage as year went on. Not sure if due to weather, location in country, fuel, or engine breaking in. Could be all of those factors.

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Old 11-25-2017, 06:27 PM   #17
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I average 7 to 7.5 but I only have the EGR. No DPF or DEF injection system. That can and will affect MPG.
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Old 11-26-2017, 12:53 PM   #18
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I'll weigh in at 5 MPG, have never hit 6. It weighs 47,000 plus towing 7,000 = 54,000 total.
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Old 12-20-2017, 11:51 AM   #19
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I'll weight in. I get 9 mpg with my ISL 35k lbs. Never heard of a ISX getting even close to me. Usually 5-7. Thats thousands of $ over 10 years.
Then the 60k more for the ISX?
Could be 75k plus more maint with ISX.
Same floor plan and layout too? Then you sit in parks or at home 98% of the time. 2% driving.
This exercize is a no brainer for many of us. Unless you rich or.....
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Old 12-20-2017, 02:40 PM   #20
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My 40 ft coach has a 350 Cummins. I run out of speedometer before I run out of power. Granted the 550 HP will get you up a long grade faster but I’m in no hurry to get anywhere.
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Old 12-20-2017, 08:45 PM   #21
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Just got a Newmar London Aire with K3-605 X15 and on 1st 1500 trip averaged 7 which is about what our 04 Essex with the 500 ISM got. The new coach wights 6,000 pounds more. The ISM got around 6 mpg the 1st 40K and then worked it's way up the 7 the next 100K.
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Old 12-21-2017, 11:37 AM   #22
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Over 47,000 miles my ISX is showing 7.6 mpg. Weight is 46,700 dry and I tow a CR-V. I did the Ugly Fix last year, seems to take longer to warm up now but runs well with no warning messages on the SilverLeaf.
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Old 12-22-2017, 07:03 AM   #23
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Firstly, no one has ever complained of having too much horsepower or torque!

Our 2011 Revolution came with the ISL, our current coach has the ISX. We're several thousand pounds heavier now yet I get almost identical mileage to what we realized with the ISL (7 to 7.5). The only "downer" is that the ISX uses a lot more DEF. The extra power is well worth it.
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Old 12-22-2017, 03:51 PM   #24
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I haven’t looked at new models recently but does the the ISL9 have a side radiator? I would assume so. Those are much easier to service. Ours is an old 2002 ISL 400HP @ 39,000lbs GCW (with tow) no problems here. Engine components very easy to get to.

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