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Good evening,

QQ: which type of oil should I use to top-up the back axle on my 2003 X350? It's a 3.5 V8. I have an advisory from the last MOT in January stating 'oil leak but not excessive'.

Advice appreciated! Thank you.

I would not recommend just topping it up. At 100K miles and my car then still serviced by a main dealer, their reaction to my request to change it was met with surprise and is not a scheduled service interval item, because like the ZF auto gearbox myth "it's filled for life sir". They would normally only check and top up and I had to press them to change it, which was not popular as there is no drain plug and means the old oil must by sucked out through the level plug filler hole. The old oil was unsurprisingly like water! It was refilled with Castrol Syntrax SAE 75W-140.

Thanks for the advice Brian - and noted about changing the axle oil. In fact my car's back at the local MOT station today, to replace the rear brake pads advised as worn when it was tested a few weeks ago. I'll get them to top up the axle oil for now, but will look to get it changed when the car has its annual service in May. Thanks again.

John,

I guess it may be too late if they were doing the work on Friday, but it's really shortsighted to go to the extent of just "topping up" the rear axle, when it would take then hardly much longer to syphon out all the oil and refill it properly, then seal the threads on the filler plug.

Good luck

Paul

Thanks for the advice Paul. I've since been told the (very slight) leak from the axle is coming from the offside driveshaft seal, so when my car is serviced in May I'll ask the garage who undertake this work (yet to be decided) to replace the leaking oil seal too. The garage which had my car last Friday is principally an MOT station, so would have been unlikely to get involved in this kind of job.

But thanks again.