Community Forums

Josh2129 · 09-01-2015, 09:12 AM

Looking for other Mountain Aire owners with the ISX12 500 hp engine and hoping to compare fuel mileage. I've had my coach for about 6 months and driven about 10,000 miles. I'm generally drive the speed limit or slower. I tow a Jeep Wrangler and rarely run the generator. My average, according to the trip computer is 6.1 mpg. I have been up to 6.3 mpg on occasion. I have a service appointment in Gaffney in October and just wondering if this is something I need to ask about. My previous coach was an Entegra Aspire with the ISL 450 hp and I got around 7.4-8 mpg. I haven't notice any more power or torque with the 500hp over the previous coach with 450. Is this normal?

John
2015 Newmar Mountain Aire 4503
2013 Jeep Wrangler Moab Edition

Stretch · 09-01-2015, 11:53 AM

Nobody so far has answered you so I'll put in my 2 cents. Our coach got about 6.3 mpg according to the built in computer. We now have 45,000 miles and it has come up a bit .25 mpg. So we have big engines hauling heavy coaches and a heavy toad. I recently added a "chip" called the Ugly Fix. I am now averaging 7.8. It is made for Detroit Series 60 engines only right now. You might look em up. I am on a long cross country trip. CA to NYC. That is where I am getting the 7.8. All of our other miles were done in mountainous ca or and wa. So I am Leary of recommending the ugly. Two other thoughts. On our coach if I cruise at 55mph the tranny will stay in fifth gear all day. I need to speed up to 60 mph and drop back to 55 to be sure it is in 6th. Also remember to push the economy button on the shift control. It changes the shift pattern to improve mileage.

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spinn · 09-01-2015, 01:02 PM

John welcome to the Newmar family. Like Stretch I can't comment directly but our ISM averages around 7 now and slips to 6.5 with the slightest bit of encouragement. I think I would look at gross weight differences between the 2 coaches as a factor. I know that others here will suggest the right RPM for you to use to max your economy

resullivan · 09-02-2015, 06:45 AM

What is your typical average engine temp running at highway speeds, 60-70 mph?

Josh2129 · 09-02-2015, 08:24 AM

I'll take a look at the temp gauge next time I have her on the road. Hanging out in Vegas for another week. Typically I think it runs cooler than the last coach. I don't remember ever seeing the temp gauge above the half way mark. (that doesn't sound very scientific).
Thank you all for the input.

John
2015 Newmar Mountain Aire 4503
2013 Jeep Wrangler Moab Edition

CampingCajun · 09-02-2015, 09:16 AM

As you put more miles on your coach the mileage should improve a little. That is a lot of weight to move down the highway & requires a bit more fuel than a smaller/lighter coach.

Scottybdivin · 09-02-2015, 09:53 AM

Quote:

Originally Posted by Josh2129

I'll take a look at the temp gauge next time I have her on the road. Hanging out in Vegas for another week. Typically I think it runs cooler than the last coach. I don't remember ever seeing the temp gauge above the half way mark. (that doesn't sound very scientific).
Thank you all for the input.

John
2015 Newmar Mountain Aire 4503
2013 Jeep Wrangler Moab Edition

What is your loaded weight? I also can't help with your ISX but I did make an interesting observation last week. We are around 43500 + 6200 for the F150. We averaged 6.3 on a 1600 mi trip to New Mexico. We got about 5.8 on the way up and 6.8 on the way down. It is amazing how much difference there is when you go from 800 to 8500 elevation and back.