MPG discussion

Topic: MPG discussion (Read 2375 times) previous topic - next topic

Re: MPG discussion

Reply #25 – July 26, 2013, 08:28:38 pm

Applause!

Re: MPG discussion

Reply #26 – July 26, 2013, 08:34:25 pm

While I may not agree with Craig on all subjects, he hits it on the head here---exactly. With a much heavier 102 inch U300, we get between 5.5 and a shade over 12 mpg. Craig will kill us on the hills and city driving as far as fuel goes but with our 3.07 rear end, 60 mph and flat ground, it is almost an equalizer on the plains. With his weight, frontal area and a lower numerical rear end, I expect he could get 14 mpg or better. Two speed rear end would be the key here like some Country Coaches have. The Cummins B engine is really excellent for everything.

If you have a 36 foot DDEC U300 you will get 12 mpg at 60 mph on flat ground, no headwind. If you don't, you need to run 110 psi in the tires COLD (and leave them alone on hot days), have proper front end alignment and not have any exhaust manifold leaks to reduce turbo pressure. New tires really reduce mileage until they are well used. You also have to make sure the transmission is locking up as that can also kill mileage (upper second, third and fourth in our 350hp DD). Full timers with lots on board and full tanks will see a little less MPG. Mechanical engines will use 3 to 5% more fuel.

Electronic mileage is great but I measure the tank with the rig exactly flat using 6 gallons per inch. I can get within one eight inch dipping it. ODO is right on.

Our old mechanical DD 4107 Buffalo bus with less weight, less frontal area and a lower numerical rear end got even better mileage, especially in hilly country.

Pierce

Re: MPG discussion

Reply #27 – July 27, 2013, 12:55:44 am

Quote from: gam – July 26, 2013, 04:17:31 pm

.For us that's about 1060 gallons of diesel and 430 gallons of gas.That's an avg of 14.76 mpg, better then pulling a 5th wheel with a pickup? Gam

One of the big reasons we got rid of the 5er and moved to a Class A was the ability to choose what we tow; boat, Jeep, glider, sedan, trailer for the in-laws, Harley on a trailer, kayaks on a trailer... my choice. The ability to tow 3 in-line notwithstanding (in some states - but not the one I live in).

That is versatility! But there were many other reasons; not the least of which was the marvelous view of the countryside which our pickup never managed to give us.

Craig

Re: MPG discussion

Reply #28 – July 27, 2013, 02:54:34 pm

Forgot to add to check air cleaner telltale as this made a big difference on ours. Replace the stock good/bad indicator with one with the numbers. Then check with DD, Cummins or Cat to see how much restriction each engine can work with. Operate at full throttle on a hill and then check the number on the telltale. You can then plan ahead for air cleaner change.

A non-contact thermometer to check for dragging brakes is another good tool to potentially increase mileage as well as giving longer pad and disk life. Something like the model below:
Non-Contact Infrared Laser Thermometer

Drive down the road and stop without using the brakes on an incline and then check brake temps for one warm or hot one. Naturally, set parking brake.

Pierce

Re: MPG discussion

Reply #29 – July 27, 2013, 03:58:52 pm

Quote from: Pierce & Gaylie Stewart – July 26, 2013, 08:34:25 pm

With his weight, frontal area and a lower numerical rear end, I expect he could get 14 mpg or better. Two speed rear end would be the key here like some Country Coaches have. The Cummins B engine is really excellent for everything.

Don't Craig and I wish!!!! I know that there are times that we can hit 14 mpg, but without a flow meter, we never see it. But it does average out in the long run to a respectable 10 to 12 mpg. I think the Banks system is helping Craig. We don't have one, but I have toyed with the idea of turning it up some. We are still stock from the factory as far as I know. But I am running synthetics. I have never seen a overall average of 12 mpg, but have way to much up and down around where I travel. Will find out if she can do better this coming winter when we head to Galveston, then hopefully west to Arizona.

Pierce mentioned the idea of a two speed rear end. Might help on down hill runs, but I doubt we would get it into high range much. The 5.9 lacks torque and power for that. I relate it a lot to the old Detroit Diesel 6-71 238hp engines the company I hauled for had when I first started. They would not get out of their own way hauling 80,000 lbs with a 13 speed underdrive Roadranger! There were hills in Pennsylvania oil country that I had my doubts of making it to the top. But they were fun to drive when empty weighting only 25,000 lbs (aluminum tankers). And we were empty almost half of our mileage. They may have been a similiar horsepower as the Cummins 5.9, but when you put that power through the Foretravel's Allison slosh-box, a lot of momentum is lost.

Re: MPG discussion

Reply #30 – July 27, 2013, 05:12:49 pm

Quote from: Pierce & Gaylie Stewart – July 27, 2013, 02:54:34 pm

A non-contact thermometer to check for dragging brakes is another good tool to potentially increase mileage as well as giving longer pad and disk life. Something like the model below:
Non-Contact Infrared Laser Thermometer

Drive down the road and stop without using the brakes on an incline and then check brake temps for one warm or hot one. Naturally, set parking brake.

Yet another RV tool that every owner should have!!! Under $40. So many uses; some of them impractical but fun ("hey, I'll bet you $10 that the hood of that toad is hot enough to fry an egg!")

We should make a list.

Craig

Re: MPG discussion

Reply #31 – July 27, 2013, 05:37:18 pm

Quote from: Dave M – July 27, 2013, 04:59:29 pm

318 & 13 speed is lil better barely.

Hey now Dave, I use to pull 8 axle Michigan steel trains cross Ontario, from Lackawanna, NY into Michigan, grossing somewhere around 135,000 lbs with that combination. That is where I found out just how much torque a 4 & a quarter Cat had when they walked away on the hills with more weight! When I graduated into a 335 Cummins, I thought I was in seventh heaven!!!

Re: MPG discussion

Reply #32 – July 27, 2013, 06:04:58 pm

Quote from: Dave M – July 26, 2013, 02:30:34 pm

I gotta fess up, the last venture Thru Wy, Mt, Co, Ka, Ok, Tx and back home over 4700 miles, the average per the VMSpc was 7.5 mpg. Considering towing the Ford pickup woth the ATV ( heavy), temps in the upper 90"s, miles of strong head winds, miles of quartering winds ant as high as 6500' elevation, and most driving in the 70+ish, am not unhappy, yes 35 mpg would be nice, but I still am in the real world.

You know that if you got 9 mpg you would have saved onlyy 100 gallons on 4700 miles or $375 or .08 a mile

Be happy

Re: MPG discussion

Reply #33 – July 27, 2013, 06:16:55 pm

Quote from: LI_Pets – July 27, 2013, 06:04:58 pm

You know that if you got 9 mpg you would have saved onlyy 100 gallons on 4700 miles or $375 or .08 a mile

Be happy

You can save a lot more than that with good fuel economy. The extra miles you can travel on a tank, coupled with the GasBuddy smartphone app, means that you can plan a trip more effectively and keep money in your wallet. Turns out that a lot of places are selling fuel priced higher than the national average. With my old pickup truck and a 5th wheel I had to re-fuel every 300 miles or so whether the price of fuel was reasonable or not. With an RV capable of going 1000 miles between fillups I can use a smartphone app to check my route for fuel at the best price; often UNDER the national average or at least less than many places along the freeway.

Then your smartphone can tell you how to get to that low-priced fuel and you can even check to see if it's easy to get to the pumps.

Craig

Re: MPG discussion

Reply #34 – July 27, 2013, 06:48:37 pm

When it's all said and done...it's like Roger said:

"How many miles per gallon?" I get this question all the time. I am happy with low 8's. range is mid 7's to mid 9's. It all depends on the roads, the wind, driving speed, towing or not and of course the driver. My answer is that our coach uses everything we put in it, sometimes faster than others. I like to include the miles and fuel used by our Jeep Wrangler and come up with a fleet average MPG rating. It is not uncommon for the Jeep to be driven 1/3 to 1/2 of the miles the coach is driven on any given trip.

I'm drivin' a 40' U320 and drive it conservatively averaging, low to mid 8's from NW coast to SE coast diagonally. I tow a Hyundai mini-station wagon, called the Elantra Touring, manual trany. and get 30-35 on it.

..so if half my mileage is above 30 and half below 10, then I'm near 20 mpg on an annual basis. That is as good as any Greenie/wishful thinker out there, or others with slide rules. I'm gonna play so gotta pay, and in the end, I don't think I'm doing bad.

Re: MPG discussion

Reply #35 – July 28, 2013, 10:45:57 am

For me, there are two main components in achieving good fuel mileage after the basics (friction: tire pressure, wax/Rejex; weight reduction; speed; mechanical).
1. Attitude - consistency in driving 'gracefully' - a soft foot on the
gas, and a soft foot on the brake. Awareness and anticipation of traffic conditions is huge.
2. Monitoring - Electronics is a huge plus - that boost gauge can be
used the same way a vacuum gauge can be used in a normally aspirated vehicle. Achieve the lowest boost for steady speed and you will be amazed at the difference at the pump.

Re: MPG discussion

Reply #36 – August 02, 2013, 06:42:47 pm

Filled fuel tank to the tippy-top... just over 75 gallons. Then 27-gallons of LPG. Then off to Scooteney Reseroir, 38 miles away, for shakedown of coach after all the work. Also did some checking on mpg with the logbook.

We have traveled 2969.5 miles since our very first fillup in December of 2011.
With the latest fillup we have put 272.463 gallons into the fuel tank.
Overall mpg for life of the coach is 10.8987 mpg.
However the last 1,124.6 miles we put 95.98 gallons of diesel into the tank for a mpg of 11.716 mpg.

I think this reflects a learning curve on my part plus the first 300 miles of driving included 200 miles through the Cascades on I-90 plus long grades up and down near the Columbia River. Even so, no trip around here is flat (even though it appears to be that way, often enough). But I am learning to drive the coach smoothly and keep the boost pressure at 10psi or below (after reading Dave Head's remarks).

So I got to thinking that while the speedometer seemed to track well with the GPS perhaps the odometer had an error. So on the way home this morning (38 miles) I checked the odometer against the mile markers along the highway and discovered that we show 0.1 miles less than we actually travel every 5 miles. So every 50 miles we actually travel 51 miles... and every 100 miles we actually travel 102 miles.

So our overall mpg is actually 11.1167mpg and the last 1200 miles is actually 11.9504 mpg.

So, not exactly 12mpg but pretty close.

Craig

Re: MPG discussion

Reply #37 – August 02, 2013, 08:53:20 pm

Dave! Don't forget that you wont be happy until and unless you wear out your generator (as stated in the past), so add fuel for that A.C. and refrigerator!

Dang, now your down to my 20 mpg average.

(old math)

Re: MPG discussion

Reply #38 – August 02, 2013, 09:01:36 pm

Quote from: Dave M – August 02, 2013, 07:17:40 pm

Finally found the secret of figuring honest fuel mileage, very simple. Coach VMSps showed 7.5 mpg, but figuring in the toad and ATV, my mileage becomes 22.5 mpg, Simple new math

Well, rats! My Wrangler only gets 17mpg so even with the new math I'm only 14.5!!!

Craig

Re: MPG discussion

Reply #39 – August 02, 2013, 09:40:07 pm

Quote from: Dave M – July 27, 2013, 04:59:29 pm

Oh yes, a 238 & a 13 sped Road Ranger works great teaching how to row your way up/ down the road as it is non stop shifting just like rowing a boat.
318 & 13 speed is lil better barely.

Barely, but a buzzin dozen warmed up good with a manual 5&4 and 4.11 gears now we getting somewhere, and oh yea straight stacks. That's why I'm near deaf but it was fun till the 1693 TA 425 Cats showed up.

Re: MPG discussion

Reply #40 – August 02, 2013, 09:56:08 pm

We get an honest 8 MPG (calculated with my wallet at the fuel island) towing the jeep most of the time running 65-70. Been the same for 8 years, all east of the big river. I suspect that will go down once we get out west, although we where out there NM, Utah, Co, MT, ID with a SOB 36' with a 5.9 towing a 20' trailer an the fuel mileage seemed to avg about the same on the round trip from Florida.

Re: MPG discussion

Reply #41 – August 02, 2013, 10:00:43 pm

Craig,

How many pickup trucks get that good mileage? A lot of older Suburbans and non-diesel trucks only see 7 mpg. Hard to believe a huge RV can be so economical. My old SOB only got 4.8 before the engine change. How much longer before everyone realizes diesels don't have to smell badly and you don't have to oil your feet and hands at the pump.

Pierce

Re: MPG discussion

Reply #42 – August 02, 2013, 11:12:57 pm

Quote from: Pierce & Gaylie Stewart – August 02, 2013, 10:00:43 pm

How many pickup trucks get that good mileage? A lot of older Suburbans and non-diesel trucks only see 7 mpg. Hard to believe a huge RV can be so economical. My old SOB only got 4.8 before the engine change. How much longer before everyone realizes diesels don't have to smell badly and you don't have to oil your feet and hands at the pump.

Pierce... we seem to be shooting ourselves in the foot here in the USA as far as "state of the art" goes. Of course, Detroit never made a car they hadn't already made... but still....

I had a 1970s Dodge Class B van that got 7mpg no matter what I did. I even installed an aftermarket cruise-control, fuel monitor computer and it still only got 7mpg. Luckily, gas was only about 70-cents a gallon; too bad I didn't have much money. I would have been overjoyed to get 11.95 mpg!!!

We bought a 1984 VW Rabbit Diesel that got 55mpg and was actually sporty to drive (as long as you didn't insist on snappy acceleration). It could out-corner most cars in the curves, too.

My 1994 Dodge 3/4-ton with the Cummins 5.9 gets about 20mpg but never got more than 11mpg towing our 29' Alpenlite 5th wheel.

Why we don't have diesel hybrid cars is beyond me; an easy 80mpg the way the Prius does it but if it were done the way a locomotive does it (the diesel generating electricity which the vehicle then uses for propulsion) we should get up into the low 100s.

Craig

Re: MPG discussion

Reply #43 – August 02, 2013, 11:44:20 pm

Quote from: wa_desert_rat – August 02, 2013, 11:12:57 pm

We bought a 1984 VW Rabbit Diesel that got 55mpg and was actually sporty to drive (as long as you didn't insist on snappy acceleration). It could out-corner most cars in the curves, too.

One of the best handling snow cars I've ever driven!!! But one that I had, had blow-by so bad that it would fill up the intake, and when you hit a hill it would just take off flying and they was no stopping til the oil got through the system. She went through all kinds of oil. The blow-by finally caught up with her

Re: MPG discussion

Reply #44 – August 03, 2013, 05:29:48 pm

We just returned from a 1700 mile journey from MI over to Niagara Falls and the Anirondack Mountians. Drove through the mountains and over to the 1000 Islands region. On a side note...a beautiful trip if you haven't seen the area spend some time there...I averaged 11.8 running between 55-63 MPH. That's using my pen and paper lol...it was out first week long trip and we are happy with it. It sure beats the 8 MPG pulling the TT with the Escalade!!

Re: MPG discussion

Reply #45 – August 10, 2013, 01:07:01 pm

With our 91GV with the 3208T cat diesel towing an 09 Ford taurus at 60 to 65 mph over a 10,000 mile trip we averaged 9.5 mpg. Trying to get an accurate mpg no. on a short trip is tricky as the fuel line to the tank is long and I have had differences of up to 5 gallons before auto shutoff. I usually go until it shuts off automatically and then top off until it wont take much more. Doing it the same way every time is important. ---- Fritz

Re: MPG discussion

Reply #46 – August 10, 2013, 04:51:21 pm

My friend drive his giant dually diesel PU and fifthwheel to TX every winter from MN for a four month stay. He says he gets about 7-8 mpg. Once there however they rarely go anywhere because that big PU only gets 8-9 w/o the fifthwheel. We were in TX and NM and points between MN there and back againg and got a pretty honest 7.9 We also put on about 1000 miles on our Wrangler which averaged about 16 mpg. We are OK with what we have. If we want to use less fuel we just don't go as far. We are planning a 3 month spring trip to SE US. We try to average about 75 miles a day. Another way to use less fuel.

Roger

Re: MPG discussion

Reply #47 – August 10, 2013, 08:43:24 pm

Short trip this summer, 3500 miles, avergaed 8.7 for entire trip. GA to CO, NE and return. One oddball fillup showed 11.2, damned if I know why, did not include that fill in overall average.
Gary B

Re: MPG discussion

Reply #48 – August 10, 2013, 10:09:17 pm

I'm going to get the MPG I get no matter what. Taking all the fuel in gallons and all the miles and doing the math it comes out to 9.0. I don't subtract for generator since in 18 years it has only 600 hours. Don't use the Aqua Hot (you can have it if you take it out and terminate all the hoses, etc.). I'm sure when in Illinois or some other flat state we might be getting maybe as high as 12 and in those with hills we could be as low as 5. Remember that, while you don't get the return on the downhill that you invested on the uphill, you do get some reprieve. I've got lots of other things to worry about than mileage here or there.

Re: MPG discussion

Reply #49 – August 10, 2013, 11:13:59 pm

Hmmm, how do you hear water?

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