Community Forums

tom chelbana · 07-04-2018, 02:06 PM

Really enjoying the extra performance here in Wyoming with the new Cummins X15 engine. From talking with other Newmar owners here at the Newmar Kountry Klub rally this is very close to what they are getting which is 7 to 7.5 miles per gallon here in the mountains and wind. The new X15 series engine is noticeably better fuel economy then our 500 ISM in our Essex. Cummins is really making progress with keeping the performance but still getting better fuel economy. A number of ISL Dutch Star owners were complaining about their poor hill pulling power. The bottom line is the new X15 doesn't use as fuel as one would think. Newmar Man

Coral · 07-04-2018, 03:02 PM

Love that big motor. It was funny when I had a oil change at Speedco last year; the truckers were coming over to check it out and could not believe they put a 600HP in a Motorhome. Since this is my first RV I really have no frame of reference to fuel economy I just feed it and go. The power in the mountains was amazing I was passing trucks like they were crawling. (I owe a thanks to IRV2 for educating me in choosing the Spartan K3 as a must have when I was shopping for a coach).

tom chelbana · 07-04-2018, 07:36 PM

The Spartan K-3 with 600 plus X-15 has to be the best chassis available today other then the 2 million dollar coaches. With the 7 plus fuel economy at 57K pounds weight it's a eye opener. Did get our London Aire weight here in Gillette at the Newmar rally and the reading were within a couple hundred pounds from those we got at the weight stations in Oregon that were closed. With 18 Dodge Durango the total comes to over 57K pounds.
Newmar Man

kdnash · 07-05-2018, 04:23 AM

I wish the dutch star (or the MA) had an option for the 605. Test drove the DS in Florida and I felt like it was lacking power. Worried about performance out west where we spend a lot of time.
David

RKLindsay · 07-05-2018, 11:31 AM

Quote:

Originally Posted by kdnash

I wish the dutch star (or the MA) had an option for the 605. Test drove the DS in Florida and I felt like it was lacking power. Worried about performance out west where we spend a lot of time.
David

The only time I feel that our 2017 could use more power is going up significant grades. I have talked to owners of coaches with 600 HP engines, and some have said that the extra HP doesn't make that much of a difference since their coach is heavier and they might be towing a much heavier tow vehicle than we do.

Mr_D · 07-05-2018, 11:42 AM

I have an ISX 650 in my CC. Over 50,000 miles it's averaging 7.6 mpg and two rebuilds due to dropped valves in #6. Wonderful power, decent fuel mileage (about the same as our previous '02 DSDP 4090 with ISC and Banks kit).
They have cured the valve breaking problem with the new head, valves, turbo and ECM programming but Cummins is refusing to do any warranty extension to cover the known problem.
The ISX 15's don't, as of yet, have the problems

kdnash · 07-06-2018, 03:11 AM

Kevin,

Thanks for the reply on the DSDP performance. I am really trying not to let a few test drives set the stage for me not getting one.
David

Dutch Star Don · 07-06-2018, 05:54 PM

I wasn't especially impressed with the performance of my 2014 Dutch Star with the ISL. My previous coach was a 2005 Monaco Diplomat with a 400 ISL. It was chipped and had a specialized radiator fan. It would pull ANY grade out west at 55+ and had the power to recover if cut off.

When I first got the Dutch Star with the 450 ISL, I almost cried on the grades. Some were held to about 47 mph in 4th gear.

I now have 40K on the coach and I'm still trying different things on hill climbs. We just returned from a 3K trip to Yellowstone where we climbed the Baker Grade into Vegas, various grades through the Teton area and into Yellowstone and then the monster grades through Oregon, Siskyous and Shasta Lake.

On the grades that are fairly straight and reasonably short, I started bumping the coach up to about 65 mph in 5th, with a good running start and pulled many grades without losing power.

In the past, on steeper hills, I was limiting my 4th gear climbing to about 47-48 mph because I felt I was over revving the engine and missing the optimum power band. This trip, I started running it harder and cranked up 4th gear to about 52 - 53 mph, turning somewhere around 2100+ rpm. The coach didn't seem to mind.

The moral of the story. When I owned my Diplomat, I would drop it into 5th, set the cruise at 55-60 mph and relax while I climbed any grade. With the Dutch Star, I can get it to climb, but I have to be very interactive with gear shifting, initial speed at the base of the grade speed and throttle control.

CP598 · 07-08-2018, 05:00 PM

Tom or Don, did either of you happen to be staying at Grizzly RV Park in West Yellowstone around July 2-4? The reason I ask is I was there and there were several Newmar MH's camped there with banners hanging from the front of the coach. Didn't get an opportunity to read the banner or stop by their camps.

TJ · 07-08-2018, 05:11 PM

Just brought our brand new Mountain Aire 4047 (K3 500 w/ISX) across Wyoming yesterday and today, Mileage was 7.4 mpg. Ran the generator most of the day yesterday while moving to use the AC. Temps were 95+ degrees outside; very comfortable inside. Today, it was cooler and we didn't need the outside AC.

Thus far, mileage is a little better than I expected for a coach with less than 2K miles on it.

TJ