We have a new 2013 Fleetwood Expedition. I thought the DEF tank was suppose to be 5 gallons. It read at the dash and the tank gauge half full. I added 2.5 gallons and it only came up to 3/4 full. I checked for the tank size in the manual and its not mentioned where I can see. Anyone know? Based on that, it sounds like 10 gallons.

What chassis?? Our Journey has a Freightliner chassis and it has a 10 gl. tank

On my Ford, the tank is five gallons. When it said it was 1/2 empty, I bought a 2-1/2 gallon container and poured it in. It took all of it. Then, the next time when it was showing 1/2 full, I put the same amount in, and it was full after only 3/4 of a bottle. I think the gauges/monitors on the DEF tank are about as accurate as the gauges on your typical RV black tank. On the good side of things, I'm getting about 1100 miles per gallon on my DEF.

DEF is Not Fuel so it has no bearing on Mileage!What it does is clean the Exhaust system and reduce pollution.

robatthelake wrote:DEF is Not Fuel so it has no bearing on Mileage!What it does is clean the Exhaust system and reduce pollution.But there is still a mileage factor to it. You consume the DEF over time and miles. Like I stated, I go about 1100 miles on one gallon of DEF. AT that rate, I could go about 5500 miles on one five gallon tank of the stuff.

On my 2013 Tiffin Pheaton with a Freightliner XCS chassis the DEF tank is 13 Gallons.

DEF tank size | Good Sam Community

TucsonJim
Explorer II
Oct 25, 2013
robatthelake wrote:
DEF is Not Fuel so it has no bearing on Mileage!

What it does is clean the Exhaust system and reduce pollution.

But there is still a mileage factor to it. You consume the DEF over time and miles. Like I stated, I go about 1100 miles on one gallon of DEF. AT that rate, I could go about 5500 miles on one five gallon tank of the stuff.
robatthelake
Explorer
Oct 25, 2013
DEF is Not Fuel so it has no bearing on Mileage!

What it does is clean the Exhaust system and reduce pollution.
TucsonJim
Explorer II
Oct 25, 2013
On my Ford, the tank is five gallons. When it said it was 1/2 empty, I bought a 2-1/2 gallon container and poured it in. It took all of it. Then, the next time when it was showing 1/2 full, I put the same amount in, and it was full after only 3/4 of a bottle. I think the gauges/monitors on the DEF tank are about as accurate as the gauges on your typical RV black tank. On the good side of things, I'm getting about 1100 miles per gallon on my DEF.
We_Cant_Wait
Explorer
Oct 24, 2013
What chassis?? Our Journey has a Freightliner chassis and it has a 10 gl. tank

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