I don't think it should be too much of an issue. If you want the thing to last obviously less is better. It can't hurt, what would it take anyways, a $35 dollar, 5L bottle of castrol that you can change in no time anyways? It's probably worth it mate I certainly would. At 89,000kms I gather it's somewhat well kept and drives well, if it was a beaten up hunk of crap with 300,000kms I'd say don't bother.