Proper XJS Convertible Top Fluid


For years so much miss-information has been spread about using transmission fluid rather than the proper top fluid as it was less costly.

I know some Jaguar dealer parts and service dept staff who tell customers this. Well here are the facts: the green oil is the proper oil to use and it is mineral oil and is the same used in Rolls and Bentley. I know from owning and servicing these cars. The only differences are the labels on the bottles when Castrol used to make it. Transmission fluid causes the seals in the pistons to swell and disintegrate then leak inside the car and when really bad, saturate the rear carpet and ruin it. Ask me how I know this? Wow! What a mess!

In the trunk/boot is the spare with a color-coded cover matching the floor and inner panel.  On the right side, there should be a matching cover over the convertible top pump assembly and there should be two turnbuckles on the front of it to fasten it to the battery tray. Please note that the top pump assembly on 93 and older is located in the storage box behind the passenger seat. The reservoir for the top pump should be 3 ¼ full and the fluid in it should be green, not red.

Therefore, if the fluid is red and low, then you will want to inspect the top pistons/cylinders that are located behind the rear panels where the quarter windows come up and go down.  Pull those panels to inspect. They are held on with plastic clips on the front of the panel and a couple on the front of the panel right behind the doors. Even if the fluid is red and to the full mark I would still inspect as someone may have seen it low and filled it not knowing that a leak was the result of a puddle on the floor under the rear seat where the pistons fluid will end up. Please understand that if the transmission fluid has been in the car long enough, the damage may have already been done so no one knows. If the fluid is red, the system should be bled and replace with the proper fluid which we have.

The recommended procedure is very much the same as bleeding the brakes. Use a vacuum hand or power pump to pull all of the fluid from the reservoir at the top of the convertible top pump motor, then put some of the mineral oil we sent to you, about 1/2 an inch in the reservoir and then operate the top to get the unwanted fluid out of the pistons into the reservoir and repeat the vacuum a couple of times until you no longer see any of the unwanted fluid mixing in with the mineral oil then once empty fill three quarters, place the bolt back in and operate a few times to get the mineral oil into the pistons then be sure you put some more into the reservoir but never above three quarters from the top where there is a hard to see full line and hopefully no earlier damage occurred to the piston seals. 


  • My further investigation into the convertible hydraulic fluid found a statement that Univis J13, MIL-H-5606A spec, was listed by Jaguar, but Univis J13 is no longer available. The article referred to Falconcrest Aviation Hydraulic oil 15, or Aeroshell, or ROYCO 756A as substitutes. ROYCO is actually MIL-PRF-5606H. I found MIL-H-5606A fluid online at an aviation supplier for $9 per quart and the color is red. Please confirm name, spec, price and color for your recommended hydraulic fluid and how to order from you.

    Eric Chance
  • Good article. What is the name and specification of the convertible top hydraulic fluid and where can I buy it. I do not see it for sale on your site.

    Eric Chance
  • My top is operating fine with the red fluid some $(%&^ was nice enough to put in there. When replacing the red fluid with the proper green fluid, if there are no leaks anywhere in the system, is it sufficient to simply replace the fluid and disregard any seal replacement? Maybe just keep an eye on it?

  • Thank you! As I own a 1995 4L convertible I did not know this.
    Cince I quite reasonably bought this car I’ll have a carful look.
    I kross my fingers that everything is all right.

    Jon Tore Jacobsen
  • Thanks! Good stuff to know!


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