ZF TE-ML, MAN 341, MB 236: what do gear oil approvals mean?

Turn over a can of mineral 80W-90 and read the back: ZF TE-ML 02B, 05A, 12L, 12M, 16C, 17H, 19B, 21A, then MAN 341, MAN 342 and Scania STO. Eight codes from ZF alone, and the salesman presents this as an argument: “The more codes, the better the oil.” It sounds logical. In fact a long list says only that the oil has been tested for many different units, and for your unit all that matters is what is specified for that very unit on its plate or in the service book.

How fluids for automatics differ from oils for manual gearboxes has already been covered in the article on fluids for transmissions, and API categories and SAE viscosity in the article on GL-4 and GL-5 gear oil. Here we deal with the codes of the makers of gearboxes, axles and trucks.

How to read a ZF TE-ML code

ZF TE-ML with a number is a ZF lubricant list, and each number belongs to a separate family of units. Here are the lists you meet most often on cans:

ZF has not maintained lists 08 and 09 (steering gears) since 1 April 2015: they are now Bosch lists.

The letter after the number is the class of lubricant within one list, and the letters mean something different in each list. In TE-ML 05, class 05A is a gear oil, while 05C is an oil with additives for limited-slip differentials. In lists 03 and 04, classes 03D and 04D are ATF, while 03A and 04A are engine oils. And in TE-ML 12, class 12G is not even an oil but a grease. So 21A and 14A have nothing in common except the letter.

Every approved oil has a list number such as ZF004860: “ZF” and six digits. The number belongs to one formulation, and one number sometimes appears against four classes from different lists. An approval is valid for 12 months and is extended only if the oil maker confirms that the formulation has not changed, and each new edition of a list replaces all the previous ones (how to check this is covered in the article on how to check an oil approval).

Why there are so many codes

The eight ZF classes from the start of the article come from the data sheet of one mineral 80W-90: truck gearboxes (02B), axles of construction machinery (05A), axles of buses and trucks (12L, 12M), rail vehicles (16C), forklifts (17H), transfer cases (19B) and tractors (21A). Hence the most frequent codes in our catalogue, too: 21A, 05A, 17B, 19B and 12L. As a rule these are ordinary 80W-90 or 75W-90 gear oils that the maker has taken through several lists. And 03D, 04D, 14A and 17C are found on ATF that ZF permits in Ecomat automatics, forklifts, marine and off-road gearboxes. The tractor lists 06 and 21 also include universal tractor oils, engine oils and ATF; why a gearbox with wet brakes is not filled with “whatever was left in the barrel” is explained in the article on oil for machinery.

In most of its lists ZF warns outright that the list merely documents lubricants tested for compatibility with its units, and is neither a recommendation nor a statement that one lubricant is better than another. So eight codes are not “eight levels of quality” but eight classes for different units, and for each unit of your vehicle only the class specified for it counts.

This applies to cars too. Classes 11A and 11B in TE-ML 11 (or, without a product list, a mineral ATF to the former Dexron II/III) are fluids only for the old three-speed and most four-speed ZF automatics. The newer five-, six-, eight- and nine-speed automatics (and the four-speed 4HP20) are filled with a special fluid (some versions of the 5HP18 are an exception), and for a fluid change ZF refers you to the part number of the carmaker’s original fluid. Although ZF calls these gearboxes maintenance-free, it advises changing the fluid at 150,000 km, and sooner under severe conditions or when the history is unknown. More in the article on universal ATF.

The interval is tied to the class

In the ZF lists, a long interval comes with the class of the oil, not with a “good” gearbox. Here is what ZF writes for gearboxes under TE-ML 02 (change at whichever comes first):

The 02E intervals apply only to gearboxes whose breather hose is routed to a dry place; without one, the 02L intervals apply (except for TraXon and buses). ZF also states separately for each group of gearboxes which classes may be used at all.

It is the same with Ecomat bus automatics: with a class 14A ATF the fluid is changed after 30,000 km or every year, with classes 14E and 14F after 150,000 km or every three years. What is more, on the first switch from 14A or 14B to a fluid with an extended interval, ZF requires an intermediate change: within 60,000 km, two years at most. Voith does the same for its DIWA automatics: a fluid to H55.6335 lasts up to 60,000 km, one to H55.6336 up to 120,000 km, and a fluid of the higher class, according to the oil makers, covers the lower one; the exact interval also depends on the type of gearbox.

Filling a class 02B oil and changing it at the 02E interval means running it at least three times longer than ZF allows. And one more thing from the same lists: any additives put into the oil afterwards change it unpredictably, so ZF does not permit them and accepts no liability for damage they cause.

Truck codes: MAN, Mercedes-Benz, Volvo, Scania, Allison

Truck makers write their own codes, and each divides them by unit:

MAN 341 is found on oils for synchromesh gearboxes (MAN’s own oil is an 80W of category GL-4), MAN 342 on oils for drive axles and final drives (GL-5), MAN 339 on ATF. I have not found in MAN’s public documents what the types after the number mean (Z2, E3, M3 and so on), so check the type against the vehicle’s documentation, not against a “similar” code.

The Mercedes-Benz 235.x sheets are gear oils for gearboxes and axles, the 236.x ones are ATF. After the group split, the truck sheets, like the engine-oil ones (see the article on oil for a truck), were given DTFR names: 12 for axle oils, 13B for manual gearbox oils, 13C for ATF.

Volvo is a good illustration of why a code is read together with the unit. Its 75W-80 oil for I-Shift gearboxes (97307, 97318) also suits older VT gearboxes, but Volvo expressly forbids it in gearboxes with overdrive (ATO), which need the 75W-90 version, and in automatics, Allison included. The same make, the same tractor unit model, two different oils.

Scania has kept separate oils for axles (letter A) and for gearboxes (letter G) since 2017. The former universal STO 1:0 is now an axle oil, although it may still be used in the gearboxes of vehicles built before 2017.

Allison recommends TES 668 fluids for its on-highway automatics; TES 295, TES 468 and TES 389 fluids remain approved, but even so Allison advises considering a switch to 668 at the next service. For each specification Allison publishes a list of approved fluids, and the data sheet of a genuinely approved fluid usually gives the approval number. In our catalogue, “Allison C-4” on ATF cans almost always comes after “meets”.

How to check a gear oil

1. The unit’s plate and the owner’s manual. On ZF gearboxes covered by lists 01 and 02 the list number is given on the type plate. For other units ZF does not promise this, so look for the code, together with the class or type, in the vehicle’s manual or service documentation.

2. The class, not just the list number. “TE-ML 02” without a letter is half a code: 02B, 02L and 02E have different intervals.

3. Approved or “meets”. In our catalogue ZF codes appear more often as approvals, whereas the Mercedes-Benz 235/236 sheets, on the contrary, appear almost twice as often as “meets”, that is, as the oil maker’s own statement. The current ZF lubricant lists are public: look the oil up by name and ZF number. Some ZF classes are defined by requirements alone, with no product list. For 07A, for example, these are API GL-5, MIL-PRF-2105E and SAE J2360, so “07A” on a can almost always follows “meets”.

4. The interval goes by the class of oil actually in the unit. If the vehicle’s history is unknown, change at the shorter interval, not the longest one in the table.

I will say it again: a gear oil is chosen by the code specified for your unit — in full, with the list, the class or the type — and not by the number of codes on the can. And if the salesman assures you that an oil with eight ZF codes “will go anywhere”, the answer is simple: it will go into the units it was tested for. Whether yours is among them, the plate on the gearbox or the vehicle’s manual will tell you.