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Topic: Fuel mileage dropped after running out of fuel. (Read 743 times) previous topic - next topic

Fuel mileage dropped after running out of fuel.

Last month, we had the bad experience of running out of fuel. Fuel gauge is not functioning correctly. During the next tank of fuel I noticed that the mpg was as much as a mile per gallon off. Drove about 800 miles. Fuel filter looks clean. Do you think running out of fuel caused the lower mpg? Also, in the last hundred miles it seems to be back to normal.

David
David West
2001 U320 40'

Re: Fuel mileage dropped after running out of fuel.

Reply #1 –
Do not see why it would, but I would love to know if there was a reason other then difference in filling.  Maybe you used the little reserve in the bottom and the refill took that into account and the next fill had it already there.
2025 Wanderbox Outpost 32 on F600 Expedition Motorhome
2015 Born Free Royal Splendor on Ford 550 nonslide version  for sale
Former Coaches  covering. 360,000 miles
1999 34 U270
2000 36 U320
2001 42' double slide U320
2018 Jeep Rubicon

Re: Fuel mileage dropped after running out of fuel.

Reply #2 –
I understand there is a way to adjust the fuel gauges to be correct.  Might call Foretravel to see how to do it or someone here may know. :D DAN
Dan & Shirley Stansel
2002 U295 4020 AGDS Build#6054
Towing Buick Enclave & M &  G Braking
Emerald Bay, Lake Palestine, Texas
MC# 16650

Re: Fuel mileage dropped after running out of fuel.

Reply #3 –
When I bought my MH, I wasn't sure if my fuel gauge was calibrated to allow for a very generous amount of warning before the tank was actually empty or just a faulty gauge which would result in the needle being on E with a full 50 gallons left in the tank (essentially a full day of driving).

However, after pumping and draining the tank for changing out the fuel lines, I realized that there must have been some crud on the sensors since the gauge is now displaying the proper amount of fuel in the tank and the gauge/sensors had been malfunctioning before.
Robert
Build # 5304
1998 34' U270 Cummins 6CTA8.3

Re: Fuel mileage dropped after running out of fuel.

Reply #4 –
The only way besides a flow meter to gauge MPG is to fill tank,  drive coach then note how much fuel is used to refill tank.  Calculation is miles since last fill up divided by gallons.

If you filled up with biodiesel your mpg will be lower than with straight diesel.  Also #2 diesel will give you more mpg than #1 or #1/#2 mix.

Biodiesel comes in various mixes i.e. B5, B20 and so on.  It should be on the pump.  Avoid the higher numbers.

Keith
Keith, Joyce & Smokey the Australian Cattle Dog
1995 U320 SE Extreme 40' WTBI Build # 4780, with a Honda CR-V hopefully still following behind.
Motorcade # 17030
FMCA # F422159

Re: Fuel mileage dropped after running out of fuel.

Reply #5 –
Fuel filter(s) now dirty? My Little VW TDI always gets a mileage boost after replacing the main fuel filter
Every day is a gift
Bob and Pat
2000 36 U295 cummins 350hp
Coach has been sold thanks to MOT 11/2016

Re: Fuel mileage dropped after running out of fuel.

Reply #6 –
I was able to tweak the adjustments on the fuel gauge sender a couple of times to get reasonable readings. When it got totally flakey, I had FOT put in a new sender. It is a new style. It seems to be working properly. About $120 for the part.
J D Stevens
1997 U295 CAI 36' Build #5085
2002 Subaru Outback
Motorcade 16869
Bellville, TX

Re: Fuel mileage dropped after running out of fuel.

Reply #7 –
I think I will look into the new part. Silver leaf is doing the calculating. Usually is dead on. Will change fuel filter after watching this next tank full. I feel the filter is the culprit.

David
David West
2001 U320 40'

Re: Fuel mileage dropped after running out of fuel.

Reply #8 –
Seems incredible running out of fuel with a VMSpc (Silverleaf), I ignore the gauge on dash and only regard the VMSpc for fuel burn. it has always been within 1 gal at a 100 gal refill.  Meaning when it sez have used 138.3 gal, a total refill was 139.2 gal.  So I have faith in it. The gauge is all over the place.
Do what makes you happy
Dave M

Re: Fuel mileage dropped after running out of fuel.

Reply #9 –
VMSpc is not an option for the C8.3 engine on our coach. The choices for measuring remaining fuel are fuel gauge, trip odometer, hour meter, or measure at the tank. I will be pleased to have a functional fuel gauge again.
J D Stevens
1997 U295 CAI 36' Build #5085
2002 Subaru Outback
Motorcade 16869
Bellville, TX

Re: Fuel mileage dropped after running out of fuel.

Reply #10 –
At some point I have decided to remove tank and cut a section out and install a glass (or other) section so the level can be viewed. Do not understand why this is not done when making tanks anyway. At least with this kind of thing it may help to see how clean the fuel is as well.
JohnH
Coachless, now use aircraft. 2003 Ford Travelair TC280 class C. Super shape. Just for 1 yr .
1994 Ford E350 ClassC,total renovation inside and out. Now sold.
2000 U295  36' Cummins 350 c/w Banks Stinger, Resonator upgrade,Solar, LED lites.Residential fridge with slide out pantry. Build 5674. Sold
ex 92 GV 022C ored Cummins. Sold
ex 95 GV240 cat 3116. Sold
2017 Mini cooper s & 2016 land Rover LR2 HSE  LUX.
jhaygarth@aol.com    SKP #130098
treat everyone as you would like to be.

Re: Fuel mileage dropped after running out of fuel.

Reply #11 –
John,

How about drilling a hole in the top and bottom side of the tank, installing shut off valves and then running a vertical sight glass? I use a stick to check fuel level and with exactly 6 gallons per inch on our U300,  it's easy to figure exactly how much fuel is left. I don't even figure how many gallons I put in or anything, just the ODO reading and gallons in the tank.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Fuel mileage dropped after running out of fuel.

Reply #12 –
I started using a measuring stick as well. Can't argue with measurement!  The issue with running out previously was Silverleaf had been reset during a trip and then lost track of that. With gauge not working correctly, we were then out in harms way and did not realize we we're off about 50 gallons. Some time went by between a few shorter trips and then it happened! Gives a lot of credence to never getting below half a tank without refilling.

Measuring stick is a piece of aluminum. I don't have calculation to how many gallons per inch, but can easily see 1/2 or 1/3 or whatever in about 5 seconds.

David
David West
2001 U320 40'

Re: Fuel mileage dropped after running out of fuel.

Reply #13 –
I don't have VMSpc on my mechanical motor.  Figure my mpg the old fashion way -  miles driven/gallons in mathematical formula.  I keep it all in a written fuel logbook, a hard cover record book.  I reset my mechanical trip meter every time I fuel up.  Try to fuel up between 400 to 600 miles.  Works well and I have a accurate, continuous, record of my miles per gallon.
1994 U225
build #4514

Re: Fuel mileage dropped after running out of fuel.

Reply #14 –
Quote from: PatC –
I don't have VMSpc on my mechanical motor.  Figure my mpg the old fashion way -  miles driven/gallons in mathematical formula.  I keep it all in a written fuel logbook, a hard cover record book.  I reset my mechanical trip meter every time I fuel up.  Try to fuel up between 400 to 600 miles.  Works well and I have a accurate, continuous, record of my miles per gallon.
Ditto! I do like having a functional fuel gauge as well.
J D Stevens
1997 U295 CAI 36' Build #5085
2002 Subaru Outback
Motorcade 16869
Bellville, TX

Re: Fuel mileage dropped after running out of fuel.

Reply #15 –
Quote from: PatC –
I don't have VMSpc on my mechanical motor.  Figure my mpg the old fashion way -  miles driven/gallons in mathematical formula.  I keep it all in a written fuel logbook, a hard cover record book.  I reset my mechanical trip meter every time I fuel up.  Try to fuel up between 400 to 600 miles.  Works well and I have a accurate, continuous, record of my miles per gallon.

I take it one step further... I don't use the "trip meter" (I use the really old fashioned method of subtracting the miles last time from the miles this time) and I calibrate the odometer using the "mile markers" on the side of most highways. I try to get ten mile markers in on a relatively flat road. My odometer reads 2% slow as of the last calibration. Then it's gallons of fuel pumped into miles driven times correction factor.

One other note: a few years back the State of California discovered an interesting way to defeat their test on gas pump accuracy. A new "chip" in the pump delivers accurate measure up to ten gallons; after that it delivers slightly less  fuel than it indicates. This worked for quite a while since the Weights and Measures inspectors typically used 1-gallon and 5-gallon containers to test the accuracy of the pump's delivery.

Craig
1993 U225 36' Unihome GV with PACBRAKE exhaust retarder, Banks Stinger and Solar Panels.
Toad: 1999 Jeep Wrangler 2-door soft-top.

"No one has ever had to evacuate a city because the solar panels broke."