AC Delco vs other DEF

Found this on the IRV site. Appears to be an email response from Blu on. how to decipher there date code for 2023.

Partimewages said:

As I suspected there isn't a expiration date just a manufacturer date.

Click to expand...

def doesn't and has never had an expiration. there is no hard rule on when def is no good anymore.

from my understanding the emissions system has nox sensor that measure nox before def injection and after and it adjusts the ammount of def used based on how much nox is being eliminated. if it is at full injection and nox is not being lowered enough it will throw a code.

the water is used to keep the urea from crystallizing. too high water content not enough nox reduction too high urea and injectors will clog.
urea degrades from uv light and heat the colder it's kept the longer it takes for it to degrade.

so there is no "expiration"

that's why I test all def before I put it in the def tank. 32.5% is what ideal def is supposed to be. do not add water to def do not add urea to def. if the mix is off when tested pour it in a garden some where and get a new box.

personally I will toss a box of def if it's under 31%. I have never seen def over 34%

I typically keep my def tank full and run it nearly empty 2 to 3 times a year usually I use a towing session to do that since it uses a lot of def while towing.

when I buy boxed def I look for boxes in pristine condition with zero damage or fading. thus is a good sign the def was stored out of the sun and fairly new. the date code is no indicator of quality.
def code with a made label of 6 months old could be bad if stored outside in direct light during a texas summer while a 3 year old jug could be good if stored inside in a cool dry back of a store.

date means nothing

According to the DEF manufacturers and distributers, DEF does have a shelf like -- about 2 years.

Shell says best shelf life when stored between 23F and 86F (-5C to +30C)
Some others recommend slightly different temperature ranges.

From Shell's product brochure:
STORAGE AND HANDLING
All DEF is designed to breakdown at elevated temperatures.
Industry standard requirements specify storage between
23° F (-5° C) to 86° F (30° C) for maximum shelf life.
The box housing the DEF bottle helps prevent exposure to
sunlight and other UV light, also helping to maintain shelf
life. DEF is typically made with a shelf life up to 2 years
from the time of manufacture. Signs of problems in storage
will include crystals forming in containers, pressurization
of sealed bottles or loss in volume


Another article about DEF storage and shelf life:
Know the Shelf Life of Diesel Exhaust Fluid - Blue Sky Diesel Exhaust Fluid (blueskydefna.com)


OWI (makers of BlueDef) says:



And lots of others