I see a lot of information for BMW 335d cars, I'm only assuming that the 4 cylinder diesel is the same. Any urea based DEF will work in a 328d? BMW, of course, is the most expensive. VW is in the middle and then apparently truck stop DEF is cheapest.
Anybody have experience with DEF working/not working?
Also, most information for DEF tanks seem to be for the 6 cylinder cars, anybody have info on tank size, active/passive tanks, etc for 328d?
Yes! DEF is DEF is DEF...is DEF.
DEF is 32.5% urea and 67.5% de-ionized water. DEF is made to an ISO standard and is used worldwide. DEF is a commodity item and it's all the same regardless of brand or where you buy it from.
I buy Peak branded DEF in 2.5 gallon jugs at my local Walmart* store and it's the cheapest of all. I DIY all DEF fills because it's so easy to do. A DEF fill in my '12 X5 35d lasts about 15k miles. I don't keep any spare DEF around because DEF is available everywhere and supposedly has a shelf life of around 1 year. I simply buy some 2.5 gallon jugs of DEF after I get the low DEF warning and the 999 miles to no-start countdown. Even with my driving around 1k miles/week that still gives me plenty of warning and time to get some fresh DEF and fill it up.
Avoid doing DEF fills from a bulk DEF dispenser at truck stops. The DEF is perfectly fine to use. The problem is the "water hammer" effect created when the DEF tank goes full can blow DEF out through the air stone vents for DEF tank. The DEF dries up and crystallizes in the air stone vents and they get clogged. So later as the car pumps DEF out of the tank, the vacuum created collapses and cracks the tank. The DEF tank is expensive to replace if this happens. BMW dealers were filling from a bulk fuel dispenser and many DEF tanks got cracked. BMW issued a Service Information Bulletin (SIB) about doing DEF fills. BMW dealers won't do a DEF fill if the DEF level reported through their diagnostic software is above a certain level. I don't know if they still use bulk fill dispensers to do DEF fills.
Only gravity fill the DEF tank with a funnel or fill from an AdBlue bottle. I recommend saving the AdBlue bottle and cut a hole in the bottom of it to use as a custom funnel for future DEF fills. Fill the DEF tank SLOWLY to let all air escape. The BMW SIB says to avoid overfilling the DEF tank but the problem is you won't know it's full until DEF overflows out the fill port. This is OK when gravity filling from a funnel or using an AdBlue bottle. It's forcing DEF in from a bulk DEF dispenser that tends to blow DEF through the air stone vents when the tank goes full. Only gravity fill the DEF tank. An easy way to check if the vents are clogged is to note whether there is a vacuum present when you open the DEF fill port. The DEF tank should not be under a vacuum. If you get a big wooosh of air going in as you open the DEF fill port, an air stone vent might be clogged.
I don't know if a 328d has 1 or 2 DEF tanks and what the capacity is. My X5 35d has 2 tanks consisting of an active tank and a passive tank. The SCR system works from the active tank and uses a transfer pump to draw DEF from the passive tank to keep the active tank filled. I suspect it was designed this way because there wasn't enough space available in a single spot to use a single tank system. The DEF capacity is required to be large enough to last a service interval (i.e., 10k miles). The total DEF capacity in my X5 35d is 5.95 US gallons. I don't know what the DEF capacity is in my 535d and whether it uses a 1 or 2 tank system.
Good luck.
