That sounds like a lot, but, did it go through and active regen or something during that time? Mine has a little over 4000kms on it now. I was at 100% DEF for somewhere above 3300kms, then it has used about 25% since then. I feel like DEF usage is not linear at all.My understanding is that it's all over the place. Mine was using to much Def. I burnt 1/4 tank in a week.