Fuel Mileage

[nealnfl]

Just drove a 2006 XL-II 1300 miles from Missouri to Florida. The best average mileage I could get was 5.3 MPG. Obviously there is something not right. I would think 6.5 should be average. Seems I have to get into the turbo more than any other coach I have driven. Any ideas for Detroit Diesel to check on?

[BrianE]

#1 suspect would be a turbo leak. A clogged injector might be suspect but would check the clamps and turbo case first. Don't know your experience so pardon if you considered use of generator.....Typically about a gallon an hour.

[Mark3101]

How fast? I don't get much more than that when running 70-75 mph. I can get better by slowing down of course.

[merle&louise]

Nealnfl,

Is the 5.3 the reading from the ProDriver or are you calculating it the old fashion way: total miles / gallons used. If you are using the ProDriver be sure to set it back to zero.

Brian brings up a good point, are you running the generator with 3 CruiseAirs running?

What are you towing?

How fast are you driving?

All of the above have to do with mpg.

I must admit though I get 7.2 mpg towing a Honda Pilot driving 65 mph and 7.7 not towing anything. If I slow down to 60 mph and not towing a vehicle I can get 8.0

[merle&louise]

Speaking of fuel mileage - has anyone noticed that the price of diesel is EQUAL to the price of REGULAR unleaded gasoline!

What's up with that? Remember when it was .50 per gallon more expensive!

I noticed that equality of price at two different truck stops in my home town. The truck stops are locally owned (not Flying Js or TA, etc.)

[jack14r]

The 06 would have the EGR engine and if you drove 75 mph or more 5.3 would not be too far off,I would check the codes in the message center display,but since you did not say anything about a CEL I doubt you have a problem.

[gmcbuffalo]

Tuga I can remember when diesel was cheaper than regular gas.

[Jon Wehrenberg]

We as observers have noted fuel consumption discussions ever since we owned our first coach. It was an 87 shell, 8V92, weighed 41,000 and over almost 15 years delivered a constant 5.6 MPG. My typical interstate speed was 62 MPH towing 3400 pounds. In 1990 when we bought our first coach and started to go to rallies owners were complaining about mileage while at the same time going to DD to get the power turned up from 475 HP to 500. Prevost was eventually convinced to up the HP on new coaches. So back then owners wanted hot rod performance but were unhappy with mileage.

Our second coach is a 96 shell, Series 60 weighing 46,600 towing 3400, 6700 or 5300 pounds. Driving the same 62 MPH highway speed, started around 8 MPG and when they started changing the fuel forumlation mileage went down and is now consistently 7.5 MPG. I still have log books with every single gallon of fuel I have ever pumped into the coaches recorded along with the mileage and location. I can also point out when I was able to buy diesel almost anywhere for $.899 per gallon.

Later coaches started getting heavier, especially those with slides, the EPA standards for the engines changed, and I noticed most owners drive at higher speeds. It all adds up. There is a huge penalty in MPG as speed increases. That is the single element totally under the control of the driver. There is a point in MPH where the mileage falls like a rock. When I have run hard in the 70 to 75 MPH range I think it costs about 1 MPG. The other factors which influence MPG are weight, over which we have a degree of control, but limited. The terrain also is a big factor because no matter how long the downhill run, it never compensates for the fuel used going up the hill. Regardless of how the coach is equipped with AC, the more AC is used the lower the mileage, but not as much as running into a 15 knot headwind for example.

I have learned a few things over the years regarding mileage. The nozzle will not always click off when filling at the same point. As a result checking mileage on a single tank is going to produce inaccurate mileage figures. I base my mileage on annual readings and the Pro-Driver and the fuel pump calculations when allowing .5 GPH for the generator hours come out almost exactly. I reset the Pro Driver at my service intervals of 5000 miles so I am looking at the equivalent of about 3 or 4 refills. At that point whether fuel is calculated or read from the Pro Driver the numbers come out the same unless there is a significant use of the generator which is not reflected in the Pro Driver, but is reflected in the cost of fuel to run the bus.

One point I will always make mostly to help myself put this into perspective is our use of fuel and its cost is chump change compared to the big picture. On newer coaches depreciation and loss of earnings on invested capital represent the largest ongoing expense associated with ownership and the difference in the cost of fuel from 5 MPG to 8 MPG even at today's prices is not much more than a rounding error when looking at the cost of ownership. I don't think we should worry about our MPG or fuel cost at the pump. I do seriously believe however if all things are constant and we see a significant change in what normal fuel consumption is then we should take note and try to determine the cause.

Regarding Neal's original post, if he drives 20,000 miles annually (a lot based on the average use by POG members) his cost for fuel at 5.3 MPG and $4.00 per gallon is $15094. At 6.5 MPG it costs $12307 or a savings of $2787. If Neal's annual usage is less than that that difference shrinks proportionately. Anybody care to guess the depreciation on a 2006 XL or the loss of earnings on the capital invested in that coach?

[phorner]

I pretty much see the same mileage as Jon.

Although we don't have that as extensive a history, we consistently get between 7.4 and 7.7 MPG. Not much variation over the last 20k miles or so.

I typically drive at 65 MPH and always tow our Hummer, although it is the lighter, H3 model. The last time I weighed our bus, it hit the GVWR right on the nose at 48,900.

[merle&louise]

I noticed today in my home town that a truck stop had diesel priced $.26 BELOW the price of unleaded gasoline!

Does anybody know why this reversal has taken placed?

I'm happy to see the reduction in price, but I was just wondering why?