04 Tropi-Cal ONLY 6mpg on Cruise & Economy Mode

[kinodeeno]

Daughter inherited vehicle a few days ago. Model T-350, Turbo CAT 350. 7800 miles. Basically empty except 1/2 tank water, full fuel, 1/2 propane, couple of cases beer & wine. No food, no clothes, no tools. Flat land cruise control in Economy Mode via I-10 So. Cal > Phoenix > Tucson at 57>63mph with 3200lb Nissan Xterra 2wd. Whopping 6 > 6.5mph on 2 different fills. Tested Air Filter gauge via push button at bottom. Factory Serviced @ 5000 miles.
Any ideas Thanks in Advance

[kinodeeno]

Daughter inherited vehicle a few days ago. Model T-350, Turbo CAT 350. 7800 miles. Basically empty except 1/2 tank water, full fuel, 1/2 propane, couple of cases beer & wine. No food, no clothes, no tools. Flat land cruise control in Economy Mode via I-10 So. Cal > Phoenix > Tucson at 57>63mph with 3200lb Nissan Xterra 2wd. Whopping 6 > 6.5mph on 2 different fills. Tested Air Filter gauge via push button at bottom. Factory Serviced @ 5000 miles.
Any ideas Thanks in Advance

[Steve & Betty]

I have an 05 and didn't get much better at that milage. It will get better as you drive it. make sure you get the valves adjusted around 12,000 or so and you will see an increase in milage. It sounds like it wasn't driven much so be patient. just to add, you will never get great gas milage with this engine. Cummins will get about 1-2 miles per gallon better according to the machanic that serviced mine last. Just make a note where all the cheap fuel is as you travel, LOL.
Steve

[bdpreece]

With my 04 which now has 32k miles on it I get about 8mpg this using my own numbers since the onboard computer lies, You really don't have enough miles on the coach yet to even say the engine is broken in. Things will get better but it will never be great. Another thing to check is what flash level the engine is at. This may require a trip to a dealer which naturally won't be cheap. Don't waste your money on the valve adjustment until at least 30K. I have talked to certified diesel mechanics who don't even recommend it then as cost effective.

[bdpreece]

Something else I was told which I actually did. Disconnnect the starting batteries reconnect then take it out and drive it like you stole it. Evidently the Allison transmission has a memory which sets shifting etc. It really made a difference in my start up from a dead stop.

[kinodeeno]

Thank You bdpreece.
Next question ... What is The Flash Level in which you commented in one of your reply's, please

[bdpreece]

The flash level is the program loaded into the ECM (electronic control module) that tells the engine how to operate. During warranty if you had problems Cat would upgrade your program for free. Out of warranty I think it is about $100 to update. Some of the changes were just for emissions and caused other problems that had to be fixed. This can be done at any Cat shop and I also believe Freightliner will do it to. You might want to join the Cat RV Club or at least check out their web site. They also have a Yahoo group for discussion on Cat only.

[Mike Canter]

A couple of items or questions here.
1. I thought I read in my Allison transmission book not to use economy mode if towing a dingy. Have they changed this recommendation in later years?
2. If you disconnect your battery and clear the memory and drive it like it is stolen I agree it will start with different logic but surely after a period of time it will change the logic back to match how you really drive? Also I don't see how that is going to change anything when the motor home is driven ata steady pace at highway speeds.
3. The Economy Mode in the Allison only changes shift points in that they are not as high in Economy Mode. This Economy Mode will not change steady state highway driving.
4. The other thing to double check is that if you are driving too slow the transmission stays in 5th gear and does not shift into 6th gear. I find that if I drive in the 55-58mph window my MH may stay in 5th gear. Check that.
5. On may MH I have a boost gauge and for better fuel economy I try and keep the boost down as low as possible while accelarating which means not keeping your foot to the floor.

[kinodeeno]

Thank You, Thank You to Everyone .....
Life Is A Learning Experience!