Who inspects the diff oil??? It,s out the back under the car out of sight!!! Ok DON,T use engine oil, use 85-140 diff oil u can buy it at superjunk, autowank, maybe even your local petrol station has some hidden behind the dogfood,and mars bars!!! Your diff will have a bung or large nut on the back plate, undo that and try to get a pinkie in there {or a piece of bent wire} dip it in to get a reading of how much oil is in there.. If nothing, damage is done, fill it up till it starts to overflow that hole.. Might last a bit longer!! Yes its a fun job getting oil into diffs, buy a squeezy bottle F.T.W..Makes it easier.. If oil already in there, diff is just worn out and you will need to replace it anyway.. Note if diff is oily and greasy that oil u just put in will leak out again so you,ll need to keep an eye on it!! Or replace the front seal... Another fun job!! Cheers Steve