Fuel Milage

[Jerry Emert]

About 1200 miles in the last week slowly going up 95 from Florida to DC and now, again slowly, going down I81 through Shenandoah.  Aladdin says I'm getting 7.5 MPG so far at about 62-65 most of the time.  Could that be accurate with this C-12.   I've seen lots of other posts saying 5-6.  Just curious, not that 1.5 means much.
Thanks
Jerry

[Steve Huber Co-Admin]

Jerry,
That's typical for the non-chipped C12s (455 hp). I get ~7.8 overall running at 65. If i run 60-62 it jumps to around 8
Steve

[Marty and Suzie Schenck]

I get 8.0 pulling my 2005 GMC 5200lb. pick-up truck and 8.7 pulling my 2014 Fiat Pop 2063lb. I have got as high as 9.5 solo on flat land. Those figures are real miles (odometer cross checked with GPS miles) divided by gallons. My Silverleaf computer is always within 1.5 gallons used. I drive between 60 and 65 with Allison set to economy mode. My coach scales in at 38,900 lb. with the pick-up behind it. Marty

[Mike Groves]

Marty,

First I'll chime in about mileage.  Mine was 8.5 on the silverleaf going east across country them coming back to the pacific coast.  But I try like crazy to keep it under 60.  As long as I get 57 and 6th gear, I'm happy.  Oh, an towing nothing.

Now, to my off topic to Marty.  My wife's car is a fiat 500 sport (like the pop outside), so what sort of modifications did you have to do to it?  Does it show much?  We got a tow setup with the coach but I've never used it.  The previous owner said he'd used it with a Jeep which is what I have, but we were more interested in tying her Fiat to it.

Thanks in advance for any info you can provide.
Mike

[Dick Simonis]

My 2000 PT with the 425 hp C-12 avg 8.5 over 20,000 miles and now my Maquis with the 505 hp seems to get a reliable 7.5 driving 65...so yeh I would think you are right in the ballbark

[Marty and Suzie Schenck]

Mike, I purchased a Roadmaster tow bracket online (can't remember from where but I will look) for $399. delivered to my house. I installed it myself with a little help from a son-in-law in 2 hours (instructions said 4). All you see in front is 2 one inch round holes that receive the towbar brackets and the electrical socket. I had to run a hot lead from the battery to the power outlet so it would be hot all the time to run my Brake Buddy. Not that I need it for extra stopping but I want it for break-a-way safety. Right now my tow lights are magnetic and they plug in just inside the rear hatch. I am sure glad I have a rear camera, I can't feel it back there. LOL Marty

[Mike Groves]

Thanks Marty,

That's what I was thinking.  Would be like towing nothing at all, plus when you use it you're getting back all the fuel economy.

Mike

[Fred Brooks]

  I get the identical mileage as Mr Huber puliing our CRV at the same speeds. Fred

[David T. Richelderfer]

I get from under 5 mpg to over 6.5 mpg, depending upon... things... which I don't know what they are.  One time on a trip from Butte to near Boise I got 6.8 mpg going down I15 to Rexburg, then on US20 to Mountain Home and filled up at the Boise Stage stop.  Several trips I have got under 5 mpg.  My estimate of mileage over the 12,000 miles I have put on this coach is between 5 and 5.5 mpg.  My toad is a 2002 Chevy Avalanche which weighs in at just over 6,000 lbs.  The coach and Avalanche weigh over 48,000 lbs when full of fuel and water.  Most of the 12,000 miles have been when pulling the Avalanche.  I usually drive from 60 to 67 mph on open roads depending upon speed limits, and I always use cruise control whenever possible.  My foot is rarely on the throttle or brake in open road driving.  I do most of my accelerating above 30 mph using the cruise control, and most of my slowing down to about 30 mph using the Jake.

The Marquis has an oil bath air filter and a reworked exhaust with a "performance" muffler.  It makes a lot of noise when accelerating and especially when the Jake is activated for slowing.  I would rather not hear what others are getting for mileage because it makes me wonder why I am not getting those efficiencies.  I would rather hear what folks have done to successfully gain mileage.  It appears the prior owner of my coach tried several things from air intake to exhaust changes to improve its mileage.  I would enjoy getting 7 to 9 mpg.  Oh well.....  As they say, "If you have to ask, then you probably can't afford it anyways."

[Mike Groves]

David,

I don't believe there's a real mystery regarding how yours compares to the older coaches.  Yours is simply heavier.  I think, for example, mine on average is probably no more than 33-34000 lbs (I am towing nothing), and I get around 8.5, so if you do the ratio mathematics, that would put yours at about 6 assuming both our numbers are right.  I've never weighed mine but I believe the max including a tow is only 36000 or so on the card up front, and so I am guessing I am not doing that. 

I believe Gerald has a heavier coach in the SMC era than most of us, given his tire pressures.  What are you getting for fuel economy Gerald?

Mike

[Dave Atherton]

Answer to your question on mileage you are doing very good on fuel mileage with C-12. I Had many many read outs on trip mileage doing Diagonostic work engines. Sometimes fuel loss will go
down when fuel filter is nearing end of it use ( needs changing.)  note: at time of new fuel filter
install ( cat 2 micron ) You have a -5 psi pressure loss in your fuel system, when fuel filter
is nearing replacement pressure loss across ( cat 2 micron ) will be at -10 psi. If you have a
Sliver leaf it should show fuel pressure loss. At this point fuel mileage should drop off and power
loss.  With today's fuel, roads, wind, speed, weight of unit all comes into play. In talking to
other C-12 owners mileage may be different but reading out your ECM history you will know
just what your engine is getting for mileage and how many gallons of fuel that engine has used.
Dave Atherton Retired Cat Mechanic

[Gerald Farris]

I have a 2 slide 40 ft. 2000 Marquis that I average a consistent 8 MPG pulling a 5200 pound Jeep GC.

Anyone who is using the tire placard behind the driver's seat for the weight of their coach may be fooling themselves in a dangerous manner. The placard on my coach states that the max vehicle weight is 36500, however I have weighed the coach 3 times and it is always from 38400 to 39000 pounds. Of the original 11R22.5 tires that came on my coach there was only the RF tire that was not overloaded at 120 PSI. That is the reason that I changed to 295/80/22.5 tires for the extra weight capacity. As a fulltimer, I know that I carry more "stuff" than the average vacationer, but I can not stress the need to weigh your coach enough, and never guess about your weight or tire inflation.

Gerald   

[Jerry Emert]

Thanks to all for replies.  I was expecting worse so I am happy especially because I am towing my Dodge 1500 4X4.  The State of Florida charges me extra because they say it weighs more than 6k.  Thanks again.
Jerry