Community Forums

HHg · 06-20-2014, 04:39 PM

My 380hp ISC is giving me 9.2 over 8,800 miles. I'm a 65 mph guy, but always pull my toad. I'm quite happy with my mileage!

Hhg

CampDaven · 06-20-2014, 05:30 PM

Quote:

Originally Posted by PushedAround

Haven't figured out how to go downhill both ways yet.

Dude! It was back in grade school when it was 3 miles to school, 3 feet of snow, and UPHILL....both ways!

For the record, my average move is about once a month, about 200 miles, and about a hundred bucks.

How many folks can say they move everything they have in the world 200 miles for a hundred bucks?

Dave (RVM1)

Smitty77 · 06-21-2014, 12:56 AM

We've been running heavy about 75% of the time on this trip to Alaska. Full water, LP, RV stocked, fuel very seldom below 2/3 thirds of a tank, grey/black tanks not always empty too. Towing CRV.

4K miles on this trip so far. Running slow and steady.

Adjusted for generator and hydrohot, 7.4 MPG.

40' coach, tag and CAPS ISL370.

I'm happy with this!

Best,
Smitty

Vsilvester · 06-21-2014, 03:27 AM

Quote:

Originally Posted by mikee409

Had to take the rig back to Houston last week to Heitman truck service. Trying to get back to work quickly I drove closer to 70 mph. Yesterday we picked up the RV at Heitmans. I had my new tow bar and towed our 2001 Jeep Cherokee back to Bridge City. Well I pushed the envelope on a long straight away and topped 75 mph for a little way. WOW my Cummins makes horsepower. Pulled into Bridge City,filled up and checked my mileage. I got 6.6 mpg

,won't be doing that again. I'm just happy to have my RV back. Mike

That's about what I get with my wrangler on the back
6.5 to 7.5 68 to 70 mph
We will be switching to a new f150 crew cab next week hope it stays close with the extra weight !
Good luck with your Rig !

Ramets · 06-21-2014, 06:18 AM

Quote:

Originally Posted by Smitty77

We've been running heavy about 75% of the time on this trip to Alaska. Full water, LP, RV stocked, fuel very seldom below 2/3 thirds of a tank, grey/black tanks not always empty too. Towing CRV.

4K miles on this trip so far. Running slow and steady.

Adjusted for generator and hydrohot, 7.4 MPG.

40' coach, tag and CAPS ISL370.

I'm happy with this!

Best,
Smitty

Smitty,
If you look at a map you'll see that your mileage will be a lot better coming back. It's all downhill from Alaska.

bobkathy95 · 06-28-2014, 05:08 PM

We are looking at several coaches in the 35 to 37 ft range. They all have either the 300 or the 340 Cummins engine. These are all new to 3yrs old. Forget the smoke that salesmen blow. What are real world expectation on fuel mileage? Assume a cruising speed of 65 mph. One computation with towing and one without a tow. Is one engine particularly better than the other? If so - in what way. And lastly, while cruising - is there any difference between driving with chassis A/C on or turning it off and running the gen set to get A/C. Thanks in advance for your help.

Steve Ownby · 06-28-2014, 07:11 PM

Quote:

Originally Posted by bobkatgifts

We are looking at several coaches in the 35 to 37 ft range. They all have either the 300 or the 340 Cummins engine. These are all new to 3yrs old. Forget the smoke that salesmen blow. What are real world expectation on fuel mileage? Assume a cruising speed of 65 mph. One computation with towing and one without a tow. Is one engine particularly better than the other? If so - in what way. And lastly, while cruising - is there any difference between driving with chassis A/C on or turning it off and running the gen set to get A/C. Thanks in advance for your help.

The hp figure doesn't tell us the engine in question. Depending on the year, these hp ratings can be either the ISB or the ISC. The ISB is the economy champ among Cummins engines but also the smallest displacement. Of great importance in diesel economy is the total weight of what the engine is moving. The ISB is normally used in coaches in the 24k to 30k GVWR range. MPG improved slightly on engines with DEF systems but the cost of the DEF eats up some of that. DEF is on engines built after '10.

Diesel coaches will achieve best MPG when driven at the lowest speed that 6th gear can be held reliability without constant downshifting. This occurs within a couple of hundred rpms of the max torque rpm. Driving technique and speed range is on primary importance in economy.

Coaches in the size & power you are looking at with a GVWR of 26-30k, should be able to turn in a MPG of 8-10.

Steve Ownby
Full time since '07

PushedAround · 06-28-2014, 08:29 PM

I'd say in the 9~10 range, based on my ISB. And in answer to your A/C question I usually just run the dash AC, but if it were really hot or very hilly I'd use the coach AC to take some load off of the motor.

Cat320 · 06-29-2014, 09:03 AM

Quote:

Originally Posted by Steve Ownby

The hp figure doesn't tell us the engine in question. Depending on the year, these hp ratings can be either the ISB or the ISC. The ISB is the economy champ among Cummins engines but also the smallest displacement. Of great importance in diesel economy is the total weight of what the engine is moving. The ISB is normally used in coaches in the 24k to 30k GVWR range. MPG improved slightly on engines with DEF systems but the cost of the DEF eats up some of that. DEF is on engines built after '10.

Diesel coaches will achieve best MPG when driven at the lowest speed that 6th gear can be held reliability without constant downshifting. This occurs within a couple of hundred rpms of the max torque rpm. Driving technique and speed range is on primary importance in economy.

Coaches in the size & power you are looking at with a GVWR of 26-30k, should be able to turn in a MPG of 8-10.

Steve Ownby
Full time since '07

Good information. There are also some older coaches that have the ILS with that HP rating. One caution, we have some friends that had a coach that weighed around 30k with an ISB. They took one long trip and sold it...not enough engine for that weight.

I average 8 to 8.5 running 60.

Gordon Dewald · 06-29-2014, 09:16 AM

May a good stiff wind be always at our back.

RayJr · 06-29-2014, 09:52 AM

My 330 C7 cat does 8 and we always tow a toad. I have seen some 5.9 cummings in older Discoverty coaches do in the 10/12 range. I can deal with 8 but talking to a guy with an old prevost with an 8V92 he got 4. Even though I do like the Prevost 4 would be a deal breaker. My old Bule Bird did 8 and it was like an armored car. Keep on rolling for tomorrow we die.

Skip426 · 06-29-2014, 10:13 AM

Quote:

Originally Posted by bobkatgifts

We are looking at several coaches in the 35 to 37 ft range. They all have either the 300 or the 340 Cummins engine. These are all new to 3yrs old. Forget the smoke that salesmen blow. What are real world expectation on fuel mileage? Assume a cruising speed of 65 mph. One computation with towing and one without a tow. Is one engine particularly better than the other? If so - in what way. And lastly, while cruising - is there any difference between driving with chassis A/C on or turning it off and running the gen set to get A/C. Thanks in advance for your help.

Along with Steve's, insight to your question. I'll throw this in, cruising I-5 in CA, at 58 mph to get into 6th gear , gives the best mileage on my rig; 9.6; throw a head wind at the shoebox , the only way to describe the aerodynamics of a motor home, and I'm below 8. This attached manual , produced by Cat, has info for all diesel owners to consider.

Dash A/C vs, roof air & genset has been discussed many times here in the forums.
JM2cW. Either way cost is $1.50 to$2. an hour , what's your comfort worth.

BTW; Welcome to iRV2.

PushedAround · 06-29-2014, 10:20 AM

Quote:

Originally Posted by Cat320

Good information. There are also some older coaches that have the ILS with that HP rating. One caution, we have some friends that had a coach that weighed around 30k with an ISB. They took one long trip and sold it...not enough engine for that weight.

I average 8 to 8.5 running 60.

Maybe they just are impatient? My ISB coach rolls at 28500 fully loaded with a 3400 pound toad, and it has performed fine for the 10,000 miles that I have had it.

bobkathy95 · 06-29-2014, 02:54 PM

Greatly appreciate all the feedback. Yes, the engine I was looking at is the ISB 300 Cummins. My current Ford V-10 30 valve runs great - but it is only good for about 7 mpg. I assume it can handle a toad - but I don't know for certain. I guess if I did that, I can forget about any respectable MPG's.