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Old 02-07-2015, 08:50 PM   #1
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How many MPGs on your DEF?

I was just wondering, how many MPGs are you getting on your DEF? It would be interesting to compare so please list your coach, GVW, motor, fuel mileage and how many MPGs you get on a gallon of DEF. I assume that most coaches have a 15 gallon DEF tank, so again I was wondering how often you have to fill it.

Larry & Cheryl Oscar, Louie, Ranger & Henry (our Springers)
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Old 02-07-2015, 10:44 PM   #2
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How many MPGs on your DEF?

Winnebago journey gvw 33,000# plus 6,500# toad. Use about 2.5 gallons per 1,500 miles. It is not a factor at about $12 for a 2.5 gallon jug. Costs me less than $50 per year at 5,000 miles. Fill it once or twice per season.

I get 10-11 mpg not pulling the toad, and 8.5 mpg pulling the toad in mountainous terrain. I don't drive slowly, 70 mph pulling the toad and 75 mph without, when conditions allow.

Love the DEF motor, clean, efficient, quiet.

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Old 02-08-2015, 07:44 AM   #3
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New coaches are set at 2% of fuel. Prier years are at 1%.
2014 Fleetwood Providence 42p
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Old 02-08-2015, 08:37 AM   #4
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To add to Pointrow, that equates to 2 gal DEF per 100 gal of fuel for newer coaches. My coach seems to be right at that 2% mark indicated by Pointrow.
Paul, Kathy, and Tux the Mini Schnauzer
2014 Tiffin Phaeton 42 LH, 2013 Honda CRV
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Old 02-08-2015, 09:38 AM   #5
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I don't understand why such large DEF tanks on motorhomes considering how far you can go on a gallon of DEF and how long old DEF can linger in a 13 to 15 gallon tank.

I've been told by a local expert to not store your MH with a lot of DEF since it can go bad when stored. This is not an issue with trucks since they travel so many miles compaired to MHs so they use the DEF up much more quickly over a short time.
John (N6BER), Joyce, Lucas (Golden Retriever mix), Bella (Great Pyrenees) and Lance (Great Pyrenees).
Tustin, CA
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Old 02-08-2015, 10:27 AM   #6
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Shelf life of DEF is determined by the temperature it is stored at. Between 12f and 86f, two years is normal. Over or under those temps, one year is normal.

As for me, the mpg is so minimal, I don't even check it. Since I put so little mileage on our mh, I normally keep it between 1/4 and 1/2 full and never put new def in unless I am going to drive it.

Ron, Sandie and Lilly
2013 Tiffin Phaeton 42LH 400 ISL | 2011 GMC Terrain SLT-2
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Old 02-08-2015, 11:23 AM   #7
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We have a 43' Dutch Star rolling down the road at 44,000 lbs. Fuel mileage is 7-8 and we use 2 1/2 gallons of DEF per 1,000 miles.

I wouldn't want a smaller tank. We run for 1,000 miles at a time, I don't want to fill it that much.

I'm hoping to start seeing stand alone DEF pumps. With the tank placement in so many different places a remote pump seems logical.
2013 DSDP 4347, all electric, 450 H.P. ISL
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Old 02-08-2015, 06:55 PM   #8
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We are between 400 and 450 mpg of DEF. Fill it about half when at Pilot at under $2.90 a gallon

Don and Nancy
[2014 40QBH Phaeton, 2015 Buick Enclave, 2yr old sisters Sara n Kaycee, Havanese, Two Segways
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