DEF warning

[AH64ID]

You also have to consider that the lower the volume of DEF is in the tank the more it will evaporate, so which is worse?

 

[lpennock]

Vapor pressure in the tank should minimize evaporation. The DEF tank isn't a wide open container any evaporation would need to travel up the fill nozzle (small opening) in order to be fully lost. The raise in humidity level in the tank is also going to reduce the rate of evaporation. So IMO the DEF deterioration to heat is the bigger issue.

 

[Signal73]

Vapor pressure in the tank should minimize evaporation. The DEF tank isn't a wide open container any evaporation would need to travel up the fill nozzle (small opening) in order to be fully lost. The raise in humidity level in the tank is also going to reduce the rate of evaporation. So IMO the DEF deterioration to heat is the bigger issue.

I agree and the surface area of def exposed to air is the same as well.

 

[AH64ID]

I agree and the surface area of def exposed to air is the same as well.

Only when static, the lower volume will have more surface area when the DEF is sloshing while driving.

 

[lpennock]

Only when static, the lower volume will have more surface area when the DEF is sloshing while driving.

I agree that there is a point that that the sloshing folds over on itself rather than increasing surface area but that is when the tank is mostly full. Anything lower than 3/4 full tank (and may even be higher) is going to see the same changes in surface area. Exception being rough 4x4 trails were the angle equals the maximum diagonal angle of the tank, then anything lower or higher than the distance between the corners is actually going to see a reduction in surface area from that maximum.