Community Forums

RVFunlovers · 05-13-2022, 07:07 PM

I searched and read several threads on the DEF usage of the Cummings 605.

I think I am burning about 5% DEF per gallon of diesel. Maybe a little more.

I am going to track this more closely for my next couple of thousand miles.

I have been using major truck stop DEF and filling up DEF when I stop for fuel and the DEF reads below half. So anywhere from below half to a third or a quarter on the DEF gauge.

I am not overly concerned about the DEF cost or usage but I want to make sure everything is running properly. My unofficial measurements is I am using a little more DEF per gallon of diesel than my 600 Cummins used.

Does 5 plus percent DEF gallon per diesel gallon sound reasonable?

I will know specifically how much DEF I am using per gallon of diesel and mile traveled after a few more top offs.

Another question should my DEF per gallon or mile change with my speed change? Doing 72 compared to 55 or 60? I have heard the miles per gallon of diesel changes with speed.

Bigrig2 · 05-13-2022, 07:21 PM

Quote:

Originally Posted by RVFunlovers

I searched and read several threads on the DEF usage of the Cummings 605.

I think I am burning about 5% DEF per gallon of diesel. Maybe a little more.

I am going to track this more closely for my next couple of thousand miles.

I have been using major truck stop DEF and filling up DEF when I stop for fuel and the DEF reads below half. So anywhere from below half to a third or a quarter on the DEF gauge.

I am not overly concerned about the DEF cost or usage but I want to make sure everything is running properly. My unofficial measurements is I am using a little more DEF per gallon of diesel than my 600 Cummins used.

Does 5 plus percent DEF gallon per diesel gallon sound reasonable?

I will know specifically how much DEF I am using per gallon of diesel and mile traveled after a few more top offs.

Another question should my DEF per gallon or mile change with my speed change? Doing 72 compared to 55 or 60? I have heard the miles per gallon of diesel changes with speed.

A quick search in IRV2 suggests your usage is in line. As well I believe the DEF usage correlates to gallons burned, not fuel efficiency (MPG).

https://www.irv2.com/forums/f123/big...-a-391050.html

Safe travels!

TXBart · 05-14-2022, 02:56 PM

24,818 miles we have used 3,567 gallons of diesel and 132 gallons of DEF which comes out to a little under 4%.

RVFunlovers · 05-14-2022, 03:00 PM

Thanks Vance.

I need to keep better records.

I think I am a little over 5% but I need to record the facts.

TXBart · 05-14-2022, 03:48 PM

Quote:

Originally Posted by RVFunlovers

Thanks Vance.

I need to keep better records.

I think I am a little over 5% but I need to record the facts.

I keep various pieces of data that are meaningless to anyone but me and often not very useful even to me. A carryover from a prior life.

Gary.Jones · 05-14-2022, 05:44 PM

Vance

I AM impressed. You keep the actual data and look at it for answers.

I just fill the tank with diesel when it needs filling and dump or pump in more DEF when the gauge gets to between half and a quarter tank but I’ve never tried to total it up.

My guess is that I consume DEF much quicker than I did with my 450

Thanks for real data.

Gary

brobox · 05-14-2022, 05:55 PM

When I moved up to the Cornerstone, the pickup for the toad came in handy for carry the extra DEF need for the 605. I am afraid to ask what that is....just glad I have a truck to carry enough.

Joedoggs · 05-14-2022, 07:16 PM

Awhile back I had questioned the same thing as my x15 uses approximately 5% def which is high compared to the smaller Cummins engines……I concluded that 4-6% def usage is normal with this engine after hearing from numerous other owners,talking with spartan,Cummins etc etc….unfortunately that seems normal..best wishes joe b 2019 king aire x-15

DoggieDaddy · 05-15-2022, 05:44 PM

You bought the big engine, for what reason is your own. It goes with more expense. Now you're worried about pennies? Oy.

RVFunlovers · 05-15-2022, 07:20 PM

Ha Ha. I am not worried about pennies. I just did not know what to really expect and think I might be using more DEF per diesel gallon than my 17 coach did.

I am going to try to track and check my usage for the next few months the way Vance does.