ATF+4 in No-Sticker Recessed Plug G260?

[Overlord475]

Doing a 5 speed swap this weekend and my donor transmission is stickerless with 17mm recessed allen drain plugs.

No local shops sell Redline MTF, and GL-4 Non-hypoid oil is difficult to find as well.
So I picked up 2 L of ATF+4.

As ATF+4 is synthetic it shouldn’t have sulfur in it that would be detrimental to the yellow metal syncros. I am unsure of the EP rating though.

Thoughts on ATF+4 in a stickerless G260?

[jlevie]

That should be fine.

[gospeed81]

I know there's many threads on this, as I've been researching for a week. I thought I was the only one with a stickerless recessed 17mm plug transmission. The fluid that I drained out of it was definitely red and did not smell like gear oil.

Is ATF+4 definitively OK for my G260?

If I find the Redline MT-90 locally can I switch to it without ill effect, or better yet, would it be beneficial to switch?

Thanks in advance.

[jlevie]

Our E30’s have sliding rocker arms and were designed in the days when oils with high levels of ZDDP ( a lubricant for sliding surfaces) was common. Most all current oils have low ZDDP content. One story is that the ZDDP is bad for catalytic converters, though cars of that era had converters and there wasn’t a high failure rate that could be directly attributed to the ZDDP levels. Another story is that modern engines don’t have the sliding surfaces and don’t need ZDDP and ZDDP in the oil is a bit of a problem for oil recyclers. I tend to believe the latter.

To limit rocker wear you want an oil with high levels of ZDDP. One “street” oil that satisfies this requirement is Amsoil Z-Rod 20w50, another is Shell Rotella T, though I have seen some data that suggests that Shell has lowered the ZDDP content slightly. While there are several racing oils that have higher ZDDP content, they don’t have the detergent packages as they are meant to be changed frequently, like after every event or two. Consequently they aren’t a good choice for a street car.

According to what I have been able to find out (bobistheoilguy.com) a Mobile-1 filter seems to be the best choice with the BMW OE or Mann filter running a close second. I have seen cheap generic filters collapse and block/limit oil flow (not a good thing).

These engines run dirtier than modern engines and have more combustion byproducts blow by than more modern engines. That builds up in the oil and can cause gunk to form, depending on the car’s typical driving cycle. An urban cycle (lots of short low speed trips) won’t get all of the engine up to the temperatures needed to boil off the condensates and gunk will form. But a primarily rural cycle with frequent weekly trips of 20 minutes in moderate weather or 30 minutes in colder weather will get all of the engine hot enough to boil off the condensates. The nicest thing you can do for an E30 that sees a mostly urban cycle is to take it out for a 30 minute run at highway speeds once a week and shorten the oil/filter change interval.

Because of the condensates you can’t take advantage of the longer life of synthetic oil. How often to change the oil and filter is determined by your driving cycle. A purely urban cycle suggests an oil/filter change every 2500-3000 miles. A rural cycle can go to the SI service interval lights.

I like Redline 75W90 (which contains friction modifiers) for limited slip differentials and Redline MTL 75W90 in the transmission. But a high quality ATF like Redline D4 also works very well, especially in colder weather..

As far as I can determine from looking at the part numbers in the BMW ETM, the internals of a G260 transmission were essentially unchanged over the production life, even though the transmissions may have a colored tag indicating what fluid to use. A factory BMW tech rep told me that the color tag was meant to indicate to a BMW tech what fluid to use to top off a transmission. He had no idea why BMW used different fluids at different points in the production run other than changes in suppliers. If you are draining the fluid and filling with fresh you can, in my opinion, ignore the tag.