assuming the mileage is over 120k, then yes, a rear diff gear oil change is worth doing. Mine came out the colour and consistency of Mellow Birds! Always remove the fill plug first. Takes just under 2 litres. More details here: AudiWorld Tech ArticlesThere is a recite for the diff oil last year?
It will be on 24/7 tho n don't no if I won't that say if I take my nana to shop or summet lol