Do older coaches get better mileage?

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Do older coaches get better mileage?

October 27, 2011, 11:32:03 am

At some point in the 1990s Foretravel changed their body styles significantly. Versions in the early 90s and the late 80s had what looks like more aerodynamic styling while later (and current) models.... not so much. This change certainly increased the useful interior space of the coaches but I am wondering if the change to a more vertical front had an effect on fuel economy. I'm sure there are Foretravel owners here who have owned both styles. Did you notice any difference that could be attributed to the body change (and not just a larger engine)?

Re: Do older coaches get better mileage?

Reply #1 – October 27, 2011, 11:50:14 am

Reasonable question. No reasonable answer.

In addition to shape changes, the following changed, with each change affecting MPG:

Weight gain

Larger engines (heavier weight and often requiring heaver transmissions, rear axle, etc).

Different transmissions (one of the few things that IMPROVED with the newer ones with 6 speeds with lock up torque converters in 2-6 gear ones).

More frontal area-- both height and width, so even the same drag coefficient would produce more aerodynamic drag.

Stricter EPA emissions requirements

But, net net is that the older coaches generally DO get better MPG than the newer ones! An honest 10 MPG AVERAGE (not just I once got one tank over...) was common on the U225, U240 and close to that on early U280's.

Our AVERAGE over 157,000 miles with every gallon recorded and calibrated speedometer is 11.3 MPG. Ya, I HAVE made some mods, but friends with stock U240's still get 10

Brett.

Re: Do older coaches get better mileage?

Reply #2 – October 27, 2011, 12:02:19 pm

Brett does keep meticulous records..Me, not so much. But, on average, with our 93 u225 we got approx 9 MPG. Don't have any accurate MPG numbers on our 95 U320. So far on our 2002 U 320 we are lucky to see 71/2 MPG. I have just started to use the economy mode, so, hopefully, that will increase. FWIW

Re: Do older coaches get better mileage?

Reply #3 – October 27, 2011, 12:22:48 pm

More to do with weight than anything else.

Re: Do older coaches get better mileage?

Reply #4 – October 27, 2011, 12:32:03 pm

Quote from: Dave Head – October 27, 2011, 12:22:48 pm

More to do with weight than anything else.

Absolutely true in hills/mountains. Aerodynamic drag a much more significant factor on flat ground than is GCW. I was surprised about this myself, but in spending a month working with the engineers at Caterpillar on the "Understanding Coach (RV) Performance" document, the physics was well laid out.

Re: Do older coaches get better mileage?

Reply #5 – October 27, 2011, 01:01:23 pm

Yes, very reasonable question but lots of factors.

Older, single bumper, lower U240s, U225s will have less frontal area, get better mileage on the flat. Will also weight less so better mileage in the hills/cities.

5.9 Cummins should get better mileage on the flat or in the hills and especially in town. Less internal friction overcomes a few more revolutions per mile plus weight is less.

36 footer will get better mileage than a 40 footer everything else being equal because of weight, most difference being in hills, cities.

Light loaded weekender will best a full timer in hills, towns especially if only partial propane, water fill.

Incorrect front end alignment can use more fuel and tires.

Pulling toad will lower mileage, a little on long trips on the plain, a lot in mountain country (and speed).

Running tires at max listed cold pressure on side of tire will give better mileage and performance. Some tire brands may get very slightly better fuel mileage. Watch the Michelin ad on TV.

Any change in altitude uses lots of fuel raising 30,000 lbs three or four thousand feet. The downhills don't make up for it. City driving out of lock-up also use a ton of fuel. Anytime you use the brakes, you use fuel getting back up to speed. Those of us living in the west will get much less mileage than you flat-landers.

Where we live is all hills so always full throttle or Jake brake. Lucky to see 5 mpg if going to local campgrounds. On the flat at 55 mph, we have gotten up to 13 mpg.

Betting a line of Foretravels with same tire pressure on the same FLAT road would get within a mile or so to the gallon at 55 mph with the low 5.9 Cummins the best of the bunch.

Re: Do older coaches get better mileage?

Reply #6 – October 27, 2011, 01:50:52 pm

1989 Grand Villa 36' with Detroit Diesel--not towing toad--hot summer day with cruise and air on--10.6MPG (forgot to mention, engine not totally broken in at 67,000 miles)

Still lots better than our 31' class C gas with 460 Ford at 4.5MPG

Re: Do older coaches get better mileage?

Reply #7 – October 27, 2011, 02:01:23 pm

Our 1997 U295 gets around 7 mpg. The engine is a Cummins C8.3-325. It is mechanical and has no electronic controls. Based on reports I have read, the newer engines with fuel injection control by electronic control units get better fuel mileage for similar loads.

Re: Do older coaches get better mileage?

Reply #8 – October 27, 2011, 02:28:16 pm

Our 1996 U295, C8.3-300, weighs about 26-27K and will get about 8mpg not towing. 7.5 towing Wrangler. This is one of the most fibbed about topics in the RV community IMHO.

Re: Do older coaches get better mileage?

Reply #9 – October 27, 2011, 04:31:53 pm

Quote from: Steve & Ginny Hill – October 27, 2011, 02:28:16 pm

This is one of the most fibbed about topics in the RV community IMHO.

LOL. No doubt about that. But lots of people just guess, too. Very few keep good records or even bother with a calculator at a fill-up.

We just bought (or at least made the deposit on) a 1993 U225. The current (almost ex) owner says he has gotten 14mpg coming out of the Cascades into the Puget Sound area. Since it's a 60-mile run down from 4,000 feet (Stevens Pass on US2) I suspect he's right. Claims 10-12mpg average but has no records; or at least hasn't shown them to me.

He has also mentioned some techniques to us about getting better mileage (like not keeping the pedal to the floor). What is the "economy mode" mentioned earlier.

We live in central Washington almost halfway between Seattle and Spokane. Our RV experience runs all the way from an old Dodge camper-van ("Van de Camp") (which got 7mpg!) to an 8-foot Alaskan camper, to a cab-over camper, to a 29-foot Alpenlight pulled by a Dodge diesel pickup, to a 19872 Streamline 21-foot trailer, to assorted tents. We also spent 5 years cruising the Pacific in a 32-foot sailboat in the 1980s (which makes us confident that we can manage life in a 36-foot motor home). My father-in-law has owned an assortment of motorhomes since the 1970s so it's pretty much in the family tradition.

And my wife is a school bus driver. I'm expecting her to give me lessons.

Thanks for the data. Nice forum you guys have here.

Re: Do older coaches get better mileage?

Reply #10 – October 27, 2011, 04:49:59 pm

Quote from: wa_desert_rat – October 27, 2011, 04:31:53 pm

He has also mentioned some techniques to us about getting better mileage (like not keeping the pedal to the floor). What is the "economy mode" mentioned earlier.

A previous thread on the mode button.
Economy, transmission

Allison Mode Switch

Re: Do older coaches get better mileage?

Reply #11 – October 27, 2011, 04:53:16 pm

Quote from: Dave Head – October 27, 2011, 12:22:48 pm

More to do with weight than anything else.

I'm going to have my DW go on a diet,

My 1994 U300 6V92 never did better than 6.9 mpg... about 17,000 miles all around USA.

Re: Do older coaches get better mileage?

Reply #12 – October 27, 2011, 05:29:05 pm

I am light loaded, but pull a Tahoe. This trip I'm using VMSpc again and my mileage has been consistent at 9 mpg this time out...

Re: Do older coaches get better mileage?

Reply #13 – October 27, 2011, 06:00:00 pm

I've been avoiding posting this as it seems anyone posting higher than normal mileages is deemed to be a liar. However on our 9k mile trip just finished, mileages and fuel pumped were carefully monitored for the first 7500 miles, at that point the odometer but not the speedo gave up the ghost. The speedo coincided exactly with speed indicated by gps so I assume the odometer was accurate also.

Area covered- South Tx - Yellowstone - Arkansas Ozarks - Smokies - S. Tx.

No toad, so nothing pulled, but a certain amount of in-town driving for grocery gettin etc. as necessary. Based on the number of coaches that blew by me, and the fact that I, in turn, passed maybe ten during the whole trip, my pace was leisurely. Mostly cruising in the high 50's to low 60's, up to an interstate cruise of 63-65, rare blasts to 70 to blow the soot out. A fair amount of cruising Yellowstone, back roads, blue ridge pkwy, 45 mph or so. My leisurely pace was somewhat driven by the fact that directional stability of this coach blo...er, is lacking. Presently addressing this.

Tire pressure lowered per Wayne at FOT to 85 front, 80 rear, Mich XZA3 LR H. Coach weighed a couple times with full fuel, provisions, tanks partial, right at 28K. Engine is 8.3 Cummins, mechanical inj., 300 hp. This is a bus style 96 U295.

10.375 mpg on the nose. That just happens to also be the mileage I got with my prior rig, an F350 4x4 diesel with a 10.6 Bigfoot camper on top. I'm real happy with the change!

Chuck

Re: Do older coaches get better mileage?

Reply #14 – October 27, 2011, 06:01:21 pm

I keep records of all mileage traveled and all fuel filled. Our average over 29,600 miles is 7.6 miles/gal and includes lots of mountains and flat.

We weigh in at 30,200 with full fuel and fresh water. and tow a ~3000 lb Subaru. Usually travel with full fresh water tank.
If we're running late to our next stop, we may run at 65-70 mph, but usually travel at 60.

99 U270, 36', Cummins ISC 350 hp.

Re: Do older coaches get better mileage?

Reply #15 – October 27, 2011, 06:25:50 pm

One thing I learned for sure is that you have to take the average mpg over lots of miles. I thought my U225 got 10 or 11 mpg at times on certain trips but the overall average was closer to 9 mpg at an average of 62 mph.

Re: Do older coaches get better mileage?

Reply #16 – October 27, 2011, 06:37:47 pm

On our 2100-mile trip last month across Colorado into Utah and Arizona and back: 9.4 mpg pulling a 2700 lb Pontiac Vibe. The U280's gross weight is around 27,000 with a C8.3 Cummins, 300 hp.

Re: Do older coaches get better mileage?

Reply #17 – October 27, 2011, 07:46:10 pm

At any given weight/horse power.
Drag is to the Square of speed.

Re: Do older coaches get better mileage?

Reply #18 – October 27, 2011, 08:14:28 pm

Quote from: Bill Chaplin – October 27, 2011, 07:46:10 pm

At any given weight/horse power.
Drag is to the Square of speed.

Yep. Slow down if your goal is fuel economy. Also, be aware of what your engine is doing. To me, driving this coach brings back very pleasant memories of years of driving VW campers...typically with blueprinted/balanced engines, you could feel/sense the power curve, hear the exhaust scavenge. Be one with it. How you attack grades is a huge factor. Also, (strapping on flame suit), there's no such thing as a fast coach. There are fast airplanes, fast cars,fast motorcycles, somewhat fast boats, but fast coaches are like fast turtles.

Quote from: Kent Speers – October 27, 2011, 06:25:50 pm

One thing I learned for sure is that you have to take the average mpg over lots of miles. I thought my U225 got 10 or 11 mpg at times on certain trips but the overall average was closer to 9 mpg at an average of 62 mph.

Yes, and diplomatically said I might add. Of course, there are other, major variables that affect economy. Headwinds are a major factor, ambient air temp is another of course elevation, humidity all figure in. "Sorry baby, the density altitude is too high today,plus we'd be bucking a 15 mph headwind, we're staying put." Good luck selling that one.

Quote from: Bob Hall – October 27, 2011, 06:37:47 pm

On our 2100-mile trip last month across Colorado into Utah and Arizona and back: 9.4 mpg pulling a 2700 lb Pontiac Vibe. The U280's gross weight is around 27,000 with a C8.3 Cummins, 300 hp.

Sounds pretty close to what I'm getting when you factor out the toad. This 8.3 mechanical engine comes in several horsepower variants, I'm guessing that the higher hp versions have larger injectors which is great when you need to go to warp, but not so when you're running at the low hp levels that economical cruise takes. Those nozzles lose efficiency when running at lower volumes.

Chuck

Re: Do older coaches get better mileage?

Reply #19 – October 27, 2011, 08:42:01 pm

Felt it was time to mention the mechanical condition of your engine, transmission, brake drag and of course the normal speed, wind, weight all make a difference, One reason the auto makers are now recommending 0W-20 lube oils, and the diesel engine makers lower oil pressure to reduce fuel burn, it takes more power/fuel to make 60 psi lube oil pressure, my ISM is 34-36 psi, I had to ask about that, all good, how I found out about the lower pressure settings. But the Biggie is the FOOT on the pedal. I can have the VMSpc show 10.0 mpg for a good while, but I get bored at that mode of driving, it also can show 3.2 mpg so normal runs from 7.2 - 8.8 it all depends on towing, speed and attitude etc.

Re: Do older coaches get better mileage?

Reply #20 – October 27, 2011, 08:52:30 pm

The bottom line is that as few miles as most of us put on our coaches each year, MPG just isn't that critical. If you are a trucker driving 100,000 miles per year plus, 1 or 2 mpg means a lot in fuel expense. At 10,000 miles per year it is not terribly significant when you consider the cost of our coaches and the cost of annual upkeep. IMHO

Re: Do older coaches get better mileage?

Reply #21 – October 27, 2011, 09:29:36 pm

Seeing these real-life numbers sure is a help for me. I understand that there are many factors that go into the final fuel economy number, but I wonder if somewhere, maybe buried in some shop manual, is a "best economy" rpm number. I realize that such a number is more of a laboratory number than a real world one, but I would think that it would certainly be a good starting place.

Experts, please add to my education.

Re: Do older coaches get better mileage?

Reply #22 – October 27, 2011, 09:42:34 pm

I feel my ISM is at its a best at 1350-1450 RPM, in general the lower the rpm the better fuel efficiency in general, In Foretravels case, I am certain Foretravel and Cummins have spent a lot of time figuring the rear gear ratio, tire size to get the best fuel burn for the average old goat that purchases these things.

Re: Do older coaches get better mileage?

Reply #23 – October 27, 2011, 10:08:54 pm

Quote from: kb0zke – October 27, 2011, 09:29:36 pm

Seeing these real-life numbers sure is a help for me. I understand that there are many factors that go into the final fuel economy number, but I wonder if somewhere, maybe buried in some shop manual, is a "best economy" rpm number. I realize that such a number is more of a laboratory number than a real world one, but I would think that it would certainly be a good starting place.

Experts, please add to my education.

I don't know if I qualify as an "expert" but I can tell you that RPM would not necessarily be an indicator of anything other than the crankshaft revolutions per minute. If you were driving on a flat road at 1500RPM you would not be using as much fuel as if you were climbing a hill at 1500RPM. There are more variables than just RPM that enter into the equation.

Re: Do older coaches get better mileage?

Reply #24 – October 27, 2011, 10:11:32 pm

Did some experimenting on the long cross country: flat road 60-63 right at 10. Bump up speed to 65-67 9.5 and 70 ish 9. I think I might get to 10.5 if I stayed at 55 but that is really hard to do as 60 feels like I'm just lumbering along. I don't think the styling amounts to much. It is weight and horsepower. I have a friend with SOB about 32' but with two slides and a Ford V10 who gets 7 driving 55-60. He doesn't believe I get 10.

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