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Fuel consumption (separate thread)
To avoid hijacking Mark’s XL2 thread below.
I was very surprised to hear that typical fuel consumption of newer coaches are 5.5 MPG or so. I understand that the old 2 cycle diesels (8V92) are fuel hogs, but am very surprised that the newest generation of diesel engines is not any better. The truckers seem to claim a 10% improvement with the newest urea injected diesels. The generation with particulate filters only may be less efficient.
I guess I’m the lucky owner of a pre-EPA diesel engine. No emissions equipment whatsoever. My engine is a 1998 Series 60 with 470hp and 155,000 mi. The coach weighs 48,000lbs.
On my recent 1,500 mile trip from Oregon to Arizona including two mountain passes, I got 7.7 MPG going between 55-62 MPH on cruise control. I admit that is going pretty slow but California insists on a 55 MPH limit if you have 3 axles or are towing and they are actively enforcing it as they are desperate for revenue. On short trips I get around 5.7 MPG. The big caveat is that I am NOT towing anything yet; my wife is following in her car. Can emissions equipment and towing explain the difference of > 2 MPG? Are the new coaches significantly heavier?
The mileage numbers are based on the Detroit ProDriver and the Silverleaf displays.
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39 Replies
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My XL2 is a 2009 Country Coach conversion, but the chasis was built in September of 2009 so it has the Series 60 515 HP, without any particulate filtering. We have always toed a Jeep unlimited 4door. Our overall average for 27000+ miles is 6.8mpg. That includes our trips out west every year over the rockies, I 70 in colorado, on the way back, and I 80 through Wyoming on the way out to Idaho. We usually drive 63 to 66 which seems to be the sweet spot mileage wise for this coach. The best we have ever averaged was 7.2 for three days headed west on I 10 with a pretty good breeze behind us.
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Homebuilder forum: subject by Ken; I bumped to top. 8.64 with 14L60 series. I don’t have answers. Seems when I ask the answer most often given is…If you can afford the coach you can afford the fuel! Not really true in my case. I could use the bus more if I could get better mileage or at least feel better about it. Does anyone have a good answer?? Bob
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The absolute sweet spot was the mid to late 90’s Series 60 coaches. John Klopp in his Royale approached 10 MPG. Until they started messing with fuel I was consistently getting 8 in my 97 which was 46,6000, and towed a 6700 lb. H2 Hummer and I used OTR. After the change in fuel formulation I dropped to 7.5 to 7.7.
The current coach is just shy of 53,000 and I still tow the H2 and use OTR all the time. I plan on 6, have gotten as high as 6.5, and as low as 5.8. I based my consumption on 5000 mile blocks and annually do a 12 month calculation. I have always recorded every gallon of fuel I put in the coach so I am confident of my averages. I have a 14L Series 60 with EGR. The EGR engines were the fuel hogs.
The good news is the Volvo engines according to Prevost are more efficient due to the EGR technology used on that engine and they are about a 1 MPG improvement. In terms of percentages that is a huge increase.
I had an 8V92 for about 15 years and it weighed 41,000 and for most of the time we had it it towed a 3400 lb. toad. It also had OTR which we used most of the time. It was geared low so it’s top speed was somewhere between 69 and 72 depending on if I was going downhill or on the flat, with or without a tailwind. I got 5.6 MPG lifetime average. I drove it at 59 to 60 MPH because of the gearing. I doubt if I could have improved the mileage no matter what I did. The last two coaches I drive at 62 mph. Why hurry? I’m already on vacation.
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I find MPG seems to be related to the number of hills or should I say mountains. Late summer of 2011 we traveled from Colorado to Maine and then home. We tried to say off Interstates once we reached Iowa. Speed was mostly 55 to 65. Total trip was about 6500 miles. ProDriver mileage for total trip was 8.4 MPG. At the time we had owned the coach for 6 years plus. This mileage for the trip was the best ever for us. Think it was slower driving and no preplanned stops. Just got home from touring a lot of Arizona driving a little more than 2000 miles with a 7.2 MPG. Our series 60 is rated 500 HP. Coach gross is 48000 pounds.
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According to my Prodriver and I think it’s close, on my last trip to
East TN (Townsend) from Nashville I averaged 9.2 MPG on summer blend
fuel at 70 MPH pulling a small trailer with my Goldwing on it. I can
beat 10 on level runs. I’ve made many mods to my ECM program and I’m
still tuning. I think I can beat 10 even in the hills. It’ll probably
be later this year before I can run the next set of program
modifications. My 8V92 got 5 to 5.5 MPG, didn’t seem to make much
different what I pulled or if I did 60 or 75 MPH. I had and still have a
3:36 final drive ratio. The difference is that I now have a .74 in top
gear instead of a 1:1 and of course a 14 liter Series 60.Ken
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From observation over the years I believe in order of impact on mileage I have found the following:
Speed (or headwind). Go fast or drive into a strong sustained headwind and mileage drops.
Hills. You never gain by coasting downhill what is lost climbing the hill.
Weight. Bus or toad, the more the engine has to work the worse the mileage.
OTR. This seems to be a couple of tenths of MPG. But keep in mind if a non OTR coach is kept at the same temps while running the generator or alternator (for inverter run AC units) the impact is likely to be the same.
That is the order of things that impact fuel consumption based on my observation. As to speed I used to do that when I was employed, but now I drive slow because it is so much more relaxing to be able to leave the cruise control on and not have to turn it on or off as I run up on slower drivers and have to wait before changing lanes to pass. The side benefit is a little better mileage but in the overall scheme of things what we pay for fuel is inconsequential compared to depreciation.
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Ken, did you do the engine/trans conversion? I would love to hear about it (in a new thread?) Things like how is the ultrashift working out? What is your rpm at 65 mph in top gear? Inquiring minds want to know.
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Most of the information is in this thread.
http://prevostcommunity.com/forum/threaddetails.asp?Category=Home+Builders&ThreadID=289
Ken
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One other thing being overlooked in this discussion is, rear differential gear ratio. I believe there are scattered about in the coaches more different ratios than the casual observer realizes. I was once told the most common is 4.56:1, don’t really know if that is true.
When someone states a high miles/gal number, one which you are nowhere near, the common reaction is to feel, I must be doing something wrong or that guy is blowing smoke up my xxx, but in fact he is correct and it is most likely due to the gear ratio of his coach.
I think your particular drive ratio will have the highest effect on your mileage over all the other reasons stated.
It is possible to get just about any ratio you want in a Prevo and it may well be worth changing out a ratio that is not compatible with your driving habits and or pocketbook. Aditionally if you go that route, consider a locking differential (that is, one which provides traction to both sides of the coach when required).
Just sayin, JIM
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I’d be very surprised to learn motorhome chassis have optional gear ratios. Generally speaking they are offered with one engine, one transmission and a standard ratio. That doesn’t mean special orders are not accepted. Unlike the 8V92 which was not happy being lugged and which had 3.36 or 3.73 gears available I think the Series 60 with the six speed transmission is set up to run around 1500 at common speeds of around 63 to 65.
Back in the 2 stroke days owners were screwing with wheel diameter, some running 24.5 wheels with 110 tires, others with 110 tires on 22.5 rims, both intended to use cheaper and more available tires than the 22.5/120 originally supplied. I don’t believe that is happening any more and drivers are sticking with the 315 tires on 22.5 rims.
I would be suspect of any mileage figures based on a single tank of fuel however.
Since I have recorded every gallon of fuel I have ever placed in any of my three coaches and I have those records available for anyone to see, I don’t even bother running a calculation on MPG until I have about a 5000 mile history. The reason is we not only vary how much fuel goes in at each refueling, we also can have single trips whose conditions are skewed, such as a two day trip eastbound across the plains with a wind at your back.
On such a trip we could not only have a huge uptick in mileage especially if the winds out of the west are in excess of 10 knots, but generally speaking we are descending in altitude. So I learned early on with my first coach that realistic averages are based on multiple refueling stops over a large number of miles. All of my coaches filled unevenly. The 97 was the worst and it would burp fuel and shut off the pump when I could still get as much as 20 gallons in it using a different pump. Then to skew the numbers even more, run the generator or Webasto or Aquahot and the numbers go down.
When I speak of MPG it is based on long term averages and it will include times I run the generator or Webasto, towing or not, running the OTR, but on heat instead of AC, etc.
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Ken thanks for joining in. Bob
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Thanks for everyone chiming in with their experiences. I’m a relatively new to these coaches, so this helps getting grounded on what is normal. Looks like 7.7 mpg not towing is not unusual.
My wife is following in our Acura MDX which gets a decent 25mpg at these highway speeds. With that our fleet average going down the highway is only 5.9 mpg. I will have to look into a towing setup. The MDX is great all around vehicle but cannot be towed. I’m pretty sure the fuel penalty for towing would be less than the 1.7mpg we are seeing today both driving.
As Jon points out, in the end these differences are a minor expense compared to depreciation and ongoing maintenance of these beasts.
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Yeah, you don’t buy one of these puppies for the fuel mileage. I never check my 8V92TA for fuel mileage and just look at it like moving a house around.
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Every H model I have owned has always been around 6 mpg 8v92,12.7 or 14 liter made no diference but I run the speed limt on the interstates
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Interesting differences reported. My H weighs 57,000 lbs. I have never gotten more then 5.8 mpg. Typically it is around 5.5 towing a Lexus GX470 SUV. Do not have ORA, do not run with generator or aqua hot running. Pulling my stacker trailer with two corvettes inside plus a golf cart drops it to around 4.3 mpg. It has been as low as 3.5 mpg Orlando to Scottsdale on I-10 with the stacker. Typically run just under 70 with cruise used as much as possible. When pulling the trailer run with mode on. We had the coach built new and mpg remains about the same since new. It is a 2006 model with just over 100,000 miles.
Is there any tuning that can be done that might improve this?
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