# Everything you ever wanted to know about about BMW diesels but where afraid to ask?



## bayoucity (Jun 11, 2010)

Flyingman said:


> Absolutely they have both!


Are you joking?


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## d geek (Nov 26, 2008)

I thought some of the X5's did not have dipsticks?


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## UncleJ (May 7, 2006)

The gassers do not have dipsticks -- only the diesels. And those are "carefully hidden" for some reason so folks don't know they have them. I think that doing away with the dipstick is a huge mistake.:tsk:


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## floydarogers (Oct 11, 2010)

UncleJ said:


> The gassers do not have dipsticks -- only the diesels. And those are "carefully hidden" for some reason so folks don't know they have them. I think that doing away with the dipstick is a huge mistake.:tsk:


I have yet to read, in any of the BMW or Porsche ones I follow, one instance of low oil causing engine damage. Yeah, there is confusion about what the yellow and red warnings mean and confusion when the sensor failed (safe and the lights went on), but not having a dipstick has not caused any problems (except for DIY'rs that can't be bothered with putting in the right amount of oil when changing it.):dunno:


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## dThree35 (Mar 23, 2012)

The attachment made for interesting reading. Nothing too illuminating for the consumer but still some nice trivia in there.

Wow, the complexity of the DDE and emissions systems used to make it 50-state legal. :yikes: Pilot injections and relays inside of piezo electric injectors :wow:



DnA Diesel said:


> Everything (or almost) you wanted to know about North American BMW diesels (the M57D30T2, a.k.a. M57Y engine).
> 
> Happy reading.
> 
> ...


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## 2010xdrive35d (Jun 19, 2019)

Very much enjoyed this read. : popcorn: Never knew how complex these engines were. Then it's a BMW diesel on top of that. Learned alot! :thumbup:


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## n1das (Jul 22, 2013)

I know this thread and the post I'm quoting are several years old but there's a lot of misinformation here that needs to be cleared up instead of getting perpetuated any further.



Max Schnell said:


> 1 - Be careful not to overfill the tank. Apparently diesel can flow over into the vent/charcoal filter and cause a check engine light. I did this once trying to "pack" the tank. BMW service instructed me not to "pack" the tank. LOL.
> 
> Now I set the pump nozzle on the first notch(slowest input). When the nozzle clicks off I wait a few seconds and hand fuel it slowly until the second click off occurs then I stop fueling. Never overflowed it since using that technique. Actually the manual says to stop fueling at the first click...that is considered "FULL".
> 
> 2 - When tightening the fuel cap don't over do it. Insert the cap into the filler neck and turn it gently until it clicks ONCE then leave it be. Over tightening will result in a check engine light.


It is perfectly safe to fully top the tank off all the way to liquid at the top of the filler neck. There is no need to allow room for expansion like with gasoline. This is a total non-issue with diesel fuel. You might want to be careful to avoid spilling diesel fuel on the car body but it is completely safe to top the tank off all the way to liquid fuel at the top of the filler neck. This is also the only way to get accurate and consistent mileage numbers.

There is no evaporative emission control system in a diesel vehicle so there is no charcoal canister or any other complex evap system stuff that gassers have. The evap system is a gasser thing and N/A to diesel. Evaporative emissions from a diesel vehicle are so low that they are a non-issue and there is no need for an evap system.

Leaving the fuel cap loose or completely off will not trigger a check engine light. It won't happen because it can't happen. Same with over-tightening the cap, if that's even possible. The tank is not a sealed system like in a gasser and there is nothing monitored in that area to trigger a check engine light because there is no evap system in a diesel vehicle.



> 3 - I don't care what the OEM recommended oil change is. I'm changing mine every 5,000 miles.


Old school is still alive and well. *Sighe*



> 4 - If you ever have the opportunity to use #1 diesel (premium) do it! It will result in much better fuel mileage.


#1 is related to Kerosene, IIRC, and is not "premium." DO NOT USE.
Only ULSD (Diesel #2) is to be used.


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## Nyc Dito (Jun 11, 2015)

n1das said:


> I know this thread and the post I'm quoting are several years old but there's a lot of misinformation here that needs to be cleared up instead of getting perpetuated any further.
> 
> It is perfectly safe to fully top the tank off all the way to liquid at the top of the filler neck. There is no need to allow room for expansion like with gasoline. This is a total non-issue with diesel fuel. You might want to be careful to avoid spilling diesel fuel on the car body but it is completely safe to top the tank off all the way to liquid fuel at the top of the filler neck. This is also the only way to get accurate and consistent mileage numbers.
> 
> ...


Good to know, thanks!

I changed my fuel cap when I first purchased the X5 35d in February.I always do that with any BMW I purchase with a gas engine. I did notice the other day, mine doesn't "click", only when turned hard enough. No light or issues like I would most likely have in a gas vehicle.


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## alacey (Mar 14, 2018)

AutoUnion said:


> BMW diesels have a heavier duty battery (at least this is what I read) than petrol models. This is because in the winter, you have to heavily rely on the electric accessories for heat before the engine has actually warmed up. The battery has to run the glow plugs, electric aux heater, heated seats, heated steering wheel, iDrive, heated active urea tank, etc before the engine is up to operating temperature. BMW (thankfully) put in a higher spec battery for this reason.


I know this is an old (but good) list, however, I will have to disagree with this. The reason for the heavier duty battery and starter is because you need more force to crank a diesel due to the much higher compression ratios and thicker oil that is generally used.


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## robnitro (Aug 3, 2016)

It's also false because when the engine is running the battery is not powering the devices but the alternator is. The only load on the battery are the preglow, computers, lights and cranking. Glow does take a lot of power, each one pulls around 20-30amps when cold for up to 30 seconds, which does require a good capacity (ah) battery, not just a high cranking one which yes, is due to the much higher compression. Our compression is approx 1.7x that of a gas engine, so figure 1.6x3 would be the cranking of a 5.1L gas engine if it was a linear slope (it's not but I don't have details on that).

Don't tell me the battery runs loads after that, as bmw and some try to say. No, voltage is above 13.5v when started which means the alternator is powering all that plus charging the battery. The only way the battery would be used once engine is on is if the voltage was below 12.5 or so, which doesn't happen unless your alternator is dying. I'm an industrial electrician with a lot of experience in dc battery/charging backup systems and the crap I hear from bmw makes me sick. In DC parallel circuits, the higher voltage source always gets the load. On AC there's more factors besides voltage like phase angle and power factor.


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## Nyc Dito (Jun 11, 2015)

Good info Robnitro, thanks. One question, whats a proper idle voltage? I just ask because in another thread you said you had 14.8v and im nowhere that, i think im at 13.8v. My battery seems in great condition though according to btool app...


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## Doug Huffman (Apr 25, 2015)

*I don't think so. Glow plugs are low mass ceramics that FLASH*



robnitro said:


> Glow does take a lot of power, each one pulls around 20-30amps when cold for up to 30 seconds, .


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## syoe (Jun 19, 2018)

Awesome post


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## robnitro (Aug 3, 2016)

So then it's less power needed with these plugs. That means that we aren't using up much amp hours then but really need the cranking amps to turn the engine over.


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## Doug Huffman (Apr 25, 2015)

High torque starter has 3:1 reduction planetary reduction gears.


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