Cleaning out a steering box

[Angle Grinder]

When I got my Flavia the Steering box was almost dry so I filled it with a modern EP 90 heavy oil. I have since bought the proper Penrite steering box lube and will be putting this in the steering box as it would appear to be the best lube for the job.

The Penrite Lube is much thicker than the EP 90 oil so I don't want to mix them.

Here's the question, has anyone got a suggestion for a way that I can get the old EP 90 oil out without removing the steering box from the car? There's no drain on the steering box so I need to try to thin the oil down with something (suggestions?) and then maybe suck or siphon it out via the filler hole.

Just wondering if anyone had a technique that they might be willing to share!

[Dilambdaman]

For this sort of thing I have a large hypodermic syringe with a piece of rubber tube instead of a needle.

Robin.

[Angle Grinder]

That must be one hell of a big hypodermic syringe  ... Are you a vet?   

[JohnMillham]

Robin's method is fine, but if the steering box isn't leaking, why not leave the 90 oil in it? The Penrite stuff (which I use) is difficult to pour, even when hot, which is presumably why it doesn't leak.
 Regards, John

[Angle Grinder]

It does leak and also I'm not sure that these modern EP oils are suitable for the job as some contain "cleaning" chemicals that might be bad for materials in old steering boxes.

[davidwheeler]

I have an "oil suction gun" from Machine Mart, £8.39 with a bit of plastic pipe on the end.  Basically this is a big metal syringe.

[lancialulu]

I topped up with 140 into my leaking box just before a 2500 mile road trip - level remained constant after that.