Fuel economy with 400 Cummins ISL

[TerryM]

We are into our first long trip with our new 34 FDDS Alpine Coach. This trip we've traveled 1437 miles from Yakima to (at this time) Apache Junction, via Jackpot, Ely, Las Vegas, Indio and Phoenix, with good days and windy days, mostly around 65 MPH but sometimes around 60 MPH. We're towing an '05 Colorado which weighs about 4,400 lbs the way it's loaded. We have about 3,300 total miles on the 400 Cummins ISL. We've gotten about 7.8 MPG so far this trip. Is this about average, or can we expect even better after a few more break-in miles? What are some others getting for mileage? By the way, I love driving this coach. I'm disappointed when I have to stop.

TerryM
'06 34 FDDS
'05 Colorado Toad

[TerryM]

We are into our first long trip with our new 34 FDDS Alpine Coach. This trip we've traveled 1437 miles from Yakima to (at this time) Apache Junction, via Jackpot, Ely, Las Vegas, Indio and Phoenix, with good days and windy days, mostly around 65 MPH but sometimes around 60 MPH. We're towing an '05 Colorado which weighs about 4,400 lbs the way it's loaded. We have about 3,300 total miles on the 400 Cummins ISL. We've gotten about 7.8 MPG so far this trip. Is this about average, or can we expect even better after a few more break-in miles? What are some others getting for mileage? By the way, I love driving this coach. I'm disappointed when I have to stop.

TerryM
'06 34 FDDS
'05 Colorado Toad

[Jim A]

We have an '04 36 MDDS with about 22,000 miles on it now. Same ISL engine. I also stay around the 65 mph range. We probably average about 8.5 mpg towing a Honda CRV, which is lighter than your toad. We took a 6 week trip to the east coast last fall and averaged 8.5 for the whole trip. Got as much as 10, and as low as 7 with a strong headwind.

If somebody gets a lot more than that, I don't want to hear about it!!

[Audrey & John]

We have an '06 36 FDDS, and it seems to have averaged about 7.2 mpg since day 1. I usually drive in economy mode, and rarely above 62 mph. We tow a Jeep Liberty. Quite honestly we're delighted to get above 8 mpg average on a trip - and we are seeing closer to that these days as compared to when we first got the coach. The mpg is calculated by our VMS system.

An owner of a 1999 Alpine told us the mileage improves once you get more miles on the engine?

Audrey

[EngineerMike]

I've got about 2700 on mine now. Started w/average in mid to high 7's, but its now up to 8.2. I did some calculations after it turned 8.0 to calibrate the rate of change, and I'm on schedule to hit about 8.3 or 8.4 ultimately. Might squeak up to 8.5 if the planets align. I drive 62, but sometimes when passing see 70+ and rising (hee hee).
BTW on last trip saw lotsa big company trucks doing in the high 50's on Hwy 40; must have made some calculation about fuel mileage vs. trucker pay rates for overtime, and opted to save the $3/gallon diesel.
I too have heard that after break-in (somewhere tween 10 & 20K) things would settle up to a steady state above the early mileage. I'm happy above 7.5. Drives like a dream.

[jerry davis]

We have a 05 36' and tow a RAV4. On our trip back to California from the Yakima rally we got about 8.5mpg cruising at 60-65 mph. We have 6k on the coach. We to, really enjoy how the coach drives.

By the way, we had a great time at the rally and met some great people with all sorts of good info for us first time coach owners

[skyguy62]

Our's is an 05 FDQS with 11,400. We arrived at the factory Friday from NH for some significant debugging. The coach was loaded close to max and we are towing an 05 Wrangler Unlimited. Having done a four conor weigh the tires were set at 110 frt and 95 rear. Mileage average was 6.85; best was on secondary hwy at 50-55 did 7.5, worst MN andND with strong hdwnds 4.8 Have to admit I am an aggressive driver with a coach that loves to GO! The two biggest factors that I have noticed is Headwinds 20 to 30 mph and putting cargo in tow car diesles like to push not pull.

[Cruzer]

Speed is the biggest factor. I don't have an Alpine, but I have the 400 ISL Cummins and my 40' coach grosses at 32,000 lbs so it's gotta be similar. We too tow a 2005 Wrangler Unlimited or a 4,660 lb Grand Cherokee Overland. It seems that the toads don't make much odf a difference but the speed sure does. Our time is limited at this point in our life and we travel some great distances to get where we want to go - which is always out west in the mountains. So, we do pick 'em up and put 'em down. If the speed limit is 75 out in Montana and Wyoming and that's what the truck traffic is going - we'll be right in there with them.

When you punch through the wind at 75 MPH there is an awful lot of drag on the coach. Slowing down 10 or even 20 MPH makes a huge difference. I've "seen" 9.1 but those conditions are rare. When moving along at 70-75 I'll find I get 6.7 MPG going westbound (uphill) and low 7's eastbound. I've gotten as low as 6.4 when doing some real serious mountain climbing. If I could drive 55 MPH I have no doubt that I'd be in the 8's but it just doesn't fit at this point in time.

Plus, as Skyguy mentioned, headwinds are just as bad because they will add just as much drag as that same amount of additional speed would. We haven't had a chance to test the toad cargo theory because we normally don't load the toad. We did have a stuffed grizzly bear in the Cherokee once (don't ask ) but being stuffed, he wasn't that heavy.

[Jim&MaryJo]

On my 04 34FDDS/10K miles (no toad), I've checked -with reasonable certainty- 2 times posting:

8.9 Yreka - Anaheim
9.0 Barstow - Cedar City -Barstow

Both times, I tend to keep up with cars running 65-75mph, even on grades.

[Wayne R]

Just finished an 850 mile trip from Kerrville Texas to Casa Grande AZ in an 05 40FDQS towing a Toyota Tundra D cab. 16600 miles, we averaged 8.0 per the Silverleaf unit. Overall since day 1 is up to 7.9. We are full timers so we are loaded heavy but have not weighed the coach.

[Cedar41]

5123 miles to the East Coast, 62 MPH, 8.5 average for the whole trip. Coach has 21000 miles, 400 Cummings.

[Tom and Patty]

We don't have the 400 ISL, but has anyone checked the mileage reported from the silverleaf against mileage calculated by fill-up and miles? Not counting the genset of course.

[SteveS]

I was parked next to a 2003 MDDS, 40 ft, 400 ISL last weekend who pulled a Jeep Liberty and his average mileage was 8.5, solid. He monitored RPM rather than speed and kept it at 1600 rpm. As for me and my 350 ISC, I run at 63 mph, tow a Jeep Libery, and just averaged 9.1 mpg covering 3600 miles the last 2 weeks.

[dgerstel]

I have a 2002 34fdds W/ 350 ISC towing a Pymouth Grand Voyger. I always check mileage by fillup and with Silverleaf VMSpc, taking gen use in to account I have found the Silverleaf to be very accurate. My normal speed is 65 to 70 and get 8.5 MPG. With fuel prices up I slowed down to 60 and got aprox. 9.3 MPG for a few trips. On one trip from Reno area to Las Vegas towing a large flatbed trailer with golf cart at 55 MPH I got 10.4 (very unusual.)

Dale