We just sold our U320 36 ft with the ISM 450. Our average mpg was 7.5 towing and driving 64 mph. We always have to climb mountain passes here where we live, my question is we now have a 40 ft. Nimbus with the ISM 500, we always tow and looking for a better mpg average. Does any one have experience with this configuration and have figured out at what speed to get best fuel burn? and or best RPM? I also recently read an article on keeping the Allison trans. in economy mode when in hilly terrain to minimize backshifting and therefore increase mpg.
The lifetime mpg of our 1999 40ft U320 is 8.5. We do our share of mountains and tow a Honda. Previous owner towed, too. On Interstates we cruise at 60 to 62, whatever it takes to stay in 6th gear. We do this in California, too, where the speed limit for us towing is 55. But as every CA driver knows, unless you do something to distinguish yourself from the other drivers and bring yourself to the attention of the CHIPs, 7mph above the stated speed limit is OK. At least I never got a ticket doing it (since 1967).
I-8 is virtually outside our door here in El Centro, CA. The speed limit is 70 and the only time drivers go that slow is on an exit ramp.
best, paul
Gary,
All modern turbo, inter-cooled diesels are most efficient at lower RPM-- at or just above peak torque RPM. The less high RPM work you do the better your MPG.
And, yes Economy Mode helps you run at those lower, more efficient RPM's.
Brett
Us - 7.2 MPG over all. 450 Cummins, 40'
Don't get me wrong, MPG is important from an engine efficiency standpoint. I monitor the MPG to ensure there is nothing getting to the point where something needs maintenance or some sort of attention. Otherwise, I knew going in that the fuel efficiency-consumption picture was dismal when going the diesel pusher route. And, since I don't travel 100,000 miles per year, the cost is not that much when compared to purchasing airline tickets and hotel rooms and all meals for a two month vacation.
I've averaged 8.3 mpg since I've owned Forrest.
Anywhere from 6.9 (a leg that includes going over Killington Mtn. in Vermont) to 9.5, depending on conditions and fuel type (ours loved B20 bio when we could find it). Life of the coach (according to VMSpc) is 7.4
Darned good for a small house :D
7.1 mpg during the two years we have had the coach. We drive 65 mph when the conditions are favorable. We have seldom used economy mode on the transmission. We usually travel with a full tank of fresh water, full tank of propane, and we run the diesel generator as needed. We tow a Jeep that weighs 4,080#. The engine is a C8.3-325 (all mechanical, no electronics) with Banks Stinger.
From NAC to Chicago with generator running for most of trip 8.9 From Chicago to U.P of Michigan 9.3 From U.P. to Chicago 9.0 (Very strong beam and stern winds). '95 U320 with M11 engine and no tow.
Keith
I've always assumed my 1999 M11's electronic MPG did not account for fuel consumed by the generator.
Yes? No?
best, paul
wife and I agreed on between 60 and 70 mph . overall mileage is 8.0 mpg, but I often see wife going 80 mph plus. She cannot tolerate riding behing a truck and has to pass. BelieveI could get better milegage if wife would cooperate.
Brett: To get into "E Mode" requires action on drivers part? Must push mode button to "E" Is this correct? If you do nothing then it will be in reg mode. Tks DAN
On the vast majority of RV's YES. We have had a couple of people post that theirs was not programmed that way???
Easy to VERIFY:
After the engine is warmed up, the next time you are accelerating from a stop up to highway speeds, do it in "regular" mode (i.e. you don't push the mode button. Do it at WOT (wide open throttle). Note the max RPM in each gear before it upshifts.
At the next stop, push the "mode" button and do the same (wide open throttle to cruising speed).
Economy mode will upshift at lower RPM!
Our over all average is 8.2. That is running the gen set as needed, Aua hot and driving average 64 mph and towing a Saturn Vue with the tanks normally full
The road and area of USA makes a large difference in your dreaded MPG games. Heck over the Christmas / New Year Holiday, I drove (no toad) from home in Va to southern Fl, (Arcadia), was easy getting over 9+ mpg, both ways, I drove my normal 65-68 mph and had a very nice trip. When traffic got heavy/crazy/nuts, I parked and slept awhile.
I have also had trips that getting 8 was a challenge, due to terrain and my attitude at the time.
So in the end, everyone can get the great mileage, it just takes some right foot sense.
My opinion
Dave M
Normally I do 63 mph. It's a good "never have to pass" speed. 8.5 towing the Tahoe. I get nervous going much over 68. In case you get the wrong impression I have no issue doing a buck and a quarter in an Audi V8 Quattro (having owned four). I just drive what is comfortable for the vehicle.
I would bet with tag I would be more comfortable with higher speeds.
That's what I do on the Interstates, too, let someone else pass. The other advantage is having a lot of real estate from me to whoever is in front of me. A real safety plus.
A pretty relaxing way to go.
best, paul
Thanks for all the input, after reading a very interesting link [Catrvclub...understanding performance] that Brett posted on another thread, its quite obvious that mph is a key factor in fuel consumption. Not worried about it, just was wondering as our salesman said we would be getting a lot less mpg with this newer coach compared to our U320.
Time will tell and, as always we will not sit at home because of fuel cost or mpg....heading over to the sand dunes at the Oregon Coast with the ATV's...."Life is Good"