Some DEF Advice For Us 3.0L Owners

[ILSilverado]

So today I decided to add DEF to the tank even though it was only showing two bars low. The manual shows if you are showing 1/2 full it will take the whole 2.5 gallon jug. Well I was showing two bars and about 3600 miles on the odo since new.

I'll be darned if it didn't take the whole dam 2.5 gallon jug. I left the engine running so I could watch the gauge as I was dumping it in. So I would say its safe to fill between 3500-4000 miles. I didn't do any towing just regular combined hwy and city driving.

[greco2003]

I don’t think the def gauge is an actually gauge though I think it estimates it based on mileage. At least that’s what it did on the Colorado’s according to the guys on the site. I can’t speak on the Silverado’s though. 

[Skip H]

My gauge was showing one digit past 1/2 and I put in 2 gallons and the gauge went to full. JFYI

[Wintersun]

Normally a gallon of DEF lasts for 100 to 125 gallons of diesel fuel burned. On the Duramax the DIC show gallons of fuel used and that is my indicator for when to add DEF.