MPG's?

[Cuffemdude]

Driving a 2007 Winnebago Tour with the 400hp Cummins. Purchased used this past spring. Have put around 3000 miles on since April. Around 25K total miles on the rig. Getting 5.8mpg's right now. Does that seem right? Was led to believe I would be seeing around 9mpg... Is that realistic?

[2 Stroker]

For a Cummins that is low, I get around 6.5 with 400 Cat.
Has the fuel filters been changed. What does the air filter indicator look like.
2 stroker

[GraySeal65]

Check filters and possibly an air leak in the cac or tubes? I have a 8.3 Cummins that does 9 th 11 MPG.

[windsorbill]

Originally Posted by Cuffemdude

Driving a 2007 Winnebago Tour with the 400hp Cummins. Purchased used this past spring. Have put around 3000 miles on since April. Around 25K total miles on the rig. Getting 5.8mpg's right now. Does that seem right? Was led to believe I would be seeing around 9mpg... Is that realistic?

I have the 400 as well and get 7.5-8 average towing the car. I doubt you'll ever see 9 over the long haul. I don't know how you drive, but if you're doing 70+ all the time, then maybe the 5.8 is a good number.

[A Traveler]

Same engine in a similar-weight coach.

Over 97,000 miles it has averaged 7.4 mpg. 5.8 is definitely on the low side. Over the long haul, you will never see 9 mpg. Maybe on one or two trips with a tailwind, but not consistently.

Headwinds can have a HUGE effect on mileage.

[Cuffemdude]

Originally Posted by 2 Stroker

For a Cummins that is low, I get around 6.5 with 400 Cat.
Has the fuel filters been changed. What does the air filter indicator look like.
2 stroker

Thanks for the advice. I'll be pulling it out of storage at the beginning of March and will have those filters examined and probably replaced.

Originally Posted by Cuffemdude

Driving a 2007 Winnebago Tour with the 400hp Cummins. Purchased used this past spring. Have put around 3000 miles on since April. Around 25K total miles on the rig. Getting 5.8mpg's right now. Does that seem right? Was led to believe I would be seeing around 9mpg... Is that realistic?

[Cuffemdude]

Originally Posted by GraySeal65

Check filters and possibly an air leak in the cac or tubes? I have a 8.3 Cummins that does 9 th 11 MPG.

Hadn't considered an air leak... I'm still a newbie... Cac it tubes?

[Cuffemdude]

Originally Posted by windsorbill

I have the 400 as well and get 7.5-8 average towing the car. I doubt you'll ever see 9 over the long haul. I don't know how you drive, but if you're doing 70+ all the time, then maybe the 5.8 is a good number.

I keep it at a respectable 60 mph... Was wondering if it improves with more mileage?

[BrianGlenn]

CAC - Charge Air Cooler

Do you have a Driver Information Centre (DIC) or Silverleaf (Digital Monitor) to monitor the engine parameters? Boost should reach about 30 psi on full throttle heavy load.

Brian

EDIT - How are you determining mileage? I calculate by hand as well as with the onboard monitoring.

PS - don't bother checking filters - if you have not replaced them recently yourself, just install new air and fuel filters.

[Shawn6596]

Originally Posted by GraySeal65

Check filters and possibly an air leak in the cac or tubes? I have a 8.3 Cummins that does 9 th 11 MPG.

I am also fairly new with DP's. What would an air leak have to do with MPG??

[BrianGlenn]

Originally Posted by Shawn6596

I am also fairly new with DP's. What would an air leak have to do with MPG??

If the air leak is downstream of where the air is measured ie MAF (Mass Air Flow) sensor then the engine is seeing less air flow than expected. Computer adds fuel to match expected air flow. If air is less - Poor burn efficiency - less MPG.

Applies to all engines - mostly affects forced (boosted) air applications - especially diesels that have higher boost values than gas engines.

Brian

[Dutch Star Don]

You have something going on, especially if you're doing the math by hand and have done it over several fill ups. If you fuel at one station and the coach is leaning left and then fuel at another and its leaning right, you can take an additional 5 gallons of fuel and really throw off your mileage. Many don't worry about their mpg until they see low numbers after several fuel ups.

I had a 2005 Monaco Diplomat with a 400 ISL that we bought new. It averaged about 8 on average. I found that when we took short trips (100-200) miles I found the mileage would get down in the mid 7's. On long trips where there was a lot of highway driving (350-500) miles, the mileage went to 8.5 mpg.

So......there are a lot of variables when it comes to checking your mileage. My 05' averaged 8.5 mpg over 9 years, but it was a short/light diesel pusher with little to no smog equipment. I drive my current coach the same way as my previous one, yet I'm only seeing 7.3 mpg average with the 450 ISL.

Your 5.3 mpg is an issue if you're doing all the calculating correctly, keeping it at 60 mph and averaging over several fuel ups.

[Mr_D]

With the '02 DSDP and ISC 350 w/Banks kit I used 8 for estimating fuel costs. Never really bothered with mpg.
Present 50,000# rig towing a CR-V is showing 7.6 mpg over 49,000 miles.
OP's mileage is definitely low if the figures are correct.

[2 Stroker]

Originally Posted by Shawn6596

I am also fairly new with DP's. What would an air leak have to do with MPG??

Like Brian said, if you don't have a factory information center you need something to see what is going on with your motor. My max boost is around 32. Most dash gauges when it comes to Water temp-Trans temp suck, off by 10 to 20 degs. Tools that plug into your ECM port gives you real time info.
There are 2 other ways to get it
1. Silverleaf
VMSpc | SilverLeaf Electronics, Inc.
2. Scangauge D
https://www.ebay.com/itm/ScanGauge-D...YAAOSwHnFVpgVp
Both do a good job, but the silverleaf gives more info at one time, love mine.
2 stroker