[JohnARM]

300 miles is not enough warning?

 

[JohnARM]

When fuel stops are more than 300 miles apart, yes.

But I thought it would say "35% full" before it would say "300 miles remaining".

The DEF tank does not need to be filled as often a the fuel tank. It is not like fuel will go 700 miles but DEF only 300. The opposite is the case.

 

[JohnARM]

What is the capacity of the DEF tank?

 

[JohnARM]

Gen 1 DEF = 4.5 Gal (17.0 L)
Gen 2 DEF = 3.8 Gal (14.4 L)

Thanks! Mine will be a Gen 2.

 

[JohnARM]

Right.
So there's no reason not to tell the driver 'I need DEF in 1000 miles', so that the driver can include it in his next fuel stop.

Really? You need the car to tell you that? Just fill it every time you get fuel if that is the case. 300 miles of warning/driving range seems plenty - even in the Mohave Desert.

In fact, 1000 mile seems excessive to the point of being ignored - causing people to run out.

 

[JohnARM]

John, you're not getting my point.
I'm saying if it's going to warn you, it should give warning in ample time so that you can take care of it without making a special stop just for the DEF. It should be programmed for driver convenience, not just to make the driver satisfy the car's needs.

Since the logical way of dealing with the DEF is to include it in your next fuel stop, 300 miles isn't long enough if you don't plan on buying fuel in the next 300 miles. I don't want to be rushing home on December 26th and get a warning "fill DEF within 300 miles" when I'm 400 miles from home, had my final fuel and meal stop half an hour ago and have to drive to work tomorrow morning. That's just stupid software making my life more difficult.

I understand. What I would prefer is a separate DEF "fuel gauge" with a warning light similar to what is used in a Class 8 truck.

Alternatively, just fill it every time. I think that "too much" warning is also problematic is my point. My ex wife had a car that had a "low fuel light" at 8 gallons (20 gallon tank). She got to the point that she just ignored the light. Three times she ran it out of gas!

Programing to taste would certainly work for me also.