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Vbp6us Vbp6us is offline
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Default Which oil do I use for the AT transmission? - 11-12-2018, 09:37 PM

I want to change the oil but I'm unsure what to change it with. What's a better oil to use?


2010 335i AT: Stock
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Ron Vogel Ron Vogel is offline
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Default 11-12-2018, 11:34 PM


Although it has been reported the Mercon SP works just fine in the ZF transmissions. do a Google search for Mercon 6hp28 and decide for yourself

Last edited by Ron Vogel; 11-13-2018 at 12:46 AM..
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BevsM3 BevsM3 is offline
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Default 11-13-2018, 04:30 PM

I went with the kit ECS sells, it comes with Redline fluid. Tranny’s been great. BTW you will need 2 more quarts as the included amount is not enough. Could not find it locally so it cost me time.

535i xdrive
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PR3CI5N335i PR3CI5N335i is offline
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Default 11-14-2018, 06:11 PM

I used the OEM transmission fluid from BMW at 80k. Never had an issue with 680whp.

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HyTeK HyTeK is offline
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Default 11-24-2018, 03:02 PM

Had Redline D6 put in at 45k miles, and now at 72k. Most of that time the car was around 400-450bhp with xdrive on a 2009 e90. Had the adaptations reset at that time. Shifts were a little slow/clunky the first 500 miles or so, but has been smooth ever since.
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BMW135xi BMW135xi is offline
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Default 11-26-2018, 08:41 PM

Factory is pretty good oil or Lifeguard 6 ZF.
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HyTeK HyTeK is offline
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Default 11-26-2018, 09:22 PM

Just for reference. This is a conversation I had with my old tuner. This is the reason I went with D6 over OEM or other fluids. Granted there was deeper discussions at the shop, but this was the beginning of the talks revolving what to use in our tranny.

I recently had with An Engineer/Transmission fluid expert friend of mine Nick, who works at an independent lab and testing facility in Sweden. His facility does independent testing of transmission fluids and their affect on wet clutch assemblies. Nick also did his internship at BMW in Munich.

Redline D4 doesn't meet DexronVI requirements, definitely due to the higher viscosity and possibly also because it might not have the same additives (hard to say, because specs don't necessarily have requirements about what or how much additives are contained, as long as it passes certain tests to meet those specs). D6 meets LG6 and DexronVI specs and is backwards compatible with DexronIII. DexronVI has more friction modifier additives and has a lower viscosity, but the additives make up for that and protect the clutches even better despite the lower viscosity. The extra friction modifiers found in DexronVI lubricants make for a better clutch engagement. It's smoother because right before the clutch plates come in contact and lock, the friction modifiers (FM are weak surface active molecules) shear off the surface reducing the sudden high friction engagement. FM are similar in principle (but different in chemistry of course) to EP (extreme pressure) additives in GL-5 gear oils, but FM works at much lower contact pressures found on clutches.
Using the D4 with only DexronIII specs would be worse in just about every way. The viscosity is slightly higher, hurting economy and it likely won't protect any better, definitely not the clutches in the case that it has fewer FM additives.
But it all depends on how they formulate their additive packages. A thicker base oil with the same additives as D6 would probably be smoother, but it's hard to say what they actually do. The D6 meets the requirements of the Lifeguard 6, so I'd see no reason why you shouldn't just use the D6. LG6 is probably fine too, but it's hard to find specifications on that.
Another note is that at -20F outside, I don't think the car shifts significantly softer(Here nick is referring to his 99 BMW 530d that he drives in sweden)than when it's 100F out with a hot transmission. The oil viscosity is something like 500 times more viscous and I think that although the perception of clutch engagement harshness is dependent on viscosity and additive packages, it's more dependent on the additives. Even a thick oil is squeezed out pretty quick as the plates are designed to do that quickly/efficiently so they will engage in close to the same time, but the additives and clutch design will determine more the harshness of the engagement. It's the final engagement that you feel, not necessarily the very short time leading up to it (the fluid film won't transmit so much anyways). The difference between D6 and the D4 at 120C (the clutch contact temperature can be up to 150C driving it hard) is pretty small, and certainly not 500x difference. It's actually about a 1.2x difference at 120C and 1.15x difference at 150C by my math.
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rcpro88 rcpro88 is offline
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Default 11-26-2018, 10:19 PM

I used the redline ATF stuff. I actually flushed the trans via the transcooler and have no issues with the car hooking up from a dig and hard knockdown shifts. Trans has 185k miles on it fyi. Did partial flush at 100k and a full at 130k. ***** SAT flash helps a lot for those with a 535i/unable to use the alpina trans flash.

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