ISL 425 engine

[Rudolph]

We have a 2008 vectra, just got back from the Washington DC rally. We averaged about 6.7 miles per gallon. When climbing a long 6 to 7%grade my speed would drop to 44 or 46 mph. We tow a grand cherokee. How do we compare to others with same engine?

[Rudolph]

We have a 2008 vectra, just got back from the Washington DC rally. We averaged about 6.7 miles per gallon. When climbing a long 6 to 7%grade my speed would drop to 44 or 46 mph. We tow a grand cherokee. How do we compare to others with same engine?

[doc]

Hi Rudolph -
We have the same engine in a Freightliner chassis. Damon 40 ft Essence. This thing is heavy! (ceramic tile floors, 4 slides etc)
We have something over 2 thousand miles on it and are getting about 7.75 mpg towing a Honda Element. Got back a few weeks ago from a trip up through Franklin NC (over the mountain), then up to Cherokee and through the park to Pigeon Forge. From there to Myrtle Beach and then back to N Georgia. We ran the genset quite a bit due to the heat. With all that we were pleased with the milage. Expect it to get better as soon as we get a few more miles on it.
The Cat engine (300 hp) we had in the previous coach was getting about 9.5 towing. It had around 40 thousand miles on a 2000 Itasca Horizon.
We don't try to set land speed records, just try to stay out of the way on interstates - 60-65ish.

[jimandsue60]

Rudolph, we have an 07 and we are really close to what you get. I don't think that the 25 hp difference from the 07's to the 08's does much more than offset all the pollution stuff added to reduce emissions. Part of the year we tow about 8000 pounds and get a little less milage than you. The other part of the year we only tow 3000 pounds (mini cooper)and get a little more than you. With the mini only we are getting 7.2 on average.

Jim

[John_Canfield]

We have the ISL 400 (same 1200 ft. pounds of torque) and usually weigh about 36000 and some change (coach + Jeep.) Last summer we averaged 7.7 MPG over an 8800 mile trip (Interstate speed of 65.) This summer we did 5600 miles, averaged 60 on Interstates, and got 7.8 MPG. Our engine is broken in - if you have less than 12-15k miles on yours, you should see your fuel economy slowly improve.

We will sometimes slow down to 45 on very long grades. If it is a fairly short grade (mile or two and 6-7%, and if we can travel our usual 60-65 mph, we will generally hold our speed within 0-5 mph variance.

Some grades are killers, though. When we were climbing the Big Horn Mountains and doing the switchbacks, we were doing 30 and in second gear. Climbing Monarch Pass in Colorado (elevation change of 5-6,000 feet in a very few miles), we were doing 30-40 (forgot exactly.)

[Pigman]

We have the ISL 425 in the Allegro bus. I tow a Chevy pickup that runs around 5200# loaded. We have over 8000 miles on it and have found that at 65-67MPH, we were getting 6.8MPG when I slowed to 55MPH it went to 7.5-7.8MPG. This is figured by miles traveled and gallons put in, not on the MMDC. We use the generator very little, and would expect no more than a one or two tenths improvement if that without the genny.

John

[jimandsue60]

I should add to my post above that I can't drive 55. 65 to 70 when allowed.

Jim

[Joe-K]

I've got the Cummins ISL 425 in an 2008 Allegro Bus. My CRV toad is lighter than John's truck behind his Bus so my combined weight of the rig and toad loaded up the way we travel is a little over 41,000lbs. Only 5,000 miles on the rig, so I expect the mileage to continue to improve for a little while.

Traveling normal speed of 65, I average 7.0 MPG. Increasing the speed to 70, the mileage drops off to 6.8. Trying to average 60 on a trip, I can get close to 8.0

[EngineerMike]

ISL 425 w/the new smog "Particulate Filter" muffler package. Had an 05 build 400 previously. Both rigs give 7.9 mpg running between 58 & 62 as a rule, some 65 mixed in for fun, towing 4000#.

I've had the particulate filter burn-off cycle kick on after running 110 gal or so of Mexican diesel thru her (non-ULSD). Worked just like Cummins folks said it would, i.e. ran for 20-30 min. w/the engine exhaust warning lite lit, no change in power or drivability.

Have 8500 on it now and love the coach, including the drivetrain.