Robert Eccles

Hi Guys,



Hoping you can help clear up a point of confusion for me regarding the appropriate fluid for the convertible top on my ’03 SL500.

I’ve come across several sources which say that Pentosin CH11S is the appropriate fluid, while others state that the OEM fluid is ZH-M. Now I use CH11S for the ABC system, but the fluid in my RCV pump is clearly not CHF11S. The current fluid is clear to yellow and has a much milder odor than CH11S – so I am guessing that it is ZH-M.

Question 1: Which is correct fluid to use, as specified by the OEM?

Question 2: Which is the better fluid to use (or is there another fluid that is even better)?

Question 3: Will mixing the two fluids create any issues? In my specific case, adding CHF11S to ZH-M.



Thanks in advance. This forum has been extremely helpful as a source of information and guidance. I'm in the process of rehabilitating my second SL500 and have dreams of moving up to a SL600 or AMG variant at some point :-)



Rob

bobterry99

The only product which is both approved and tested by M-B is their Hydraulikol, which may be labeled "ZH-M". Still, Pentosin states that their 11HS is intended for use in convertible top systems, so no doubt either fluid will work perfectly fine. Both a friend and I use Pentosin and have mixed it with the original fluid on at least half a dozen cars with no noticeable side effects.

Robert Eccles

Thanks @bobterry99

I picked up a bottle of the Hydraulikol from my local MB dealer here outside Houston for $16 and used a syringe to top up the reservoir of the Vario Roof Hydraulic Pump.

FxFormat

Pentosin will work fine but if it leaks out, the smell will stay with you for a long time.