I have Infiniti I30 97. Oil was leaking from oil pan gasket long time. Would find a few 1-2 square inch drops in morning. But last a few months I can see in morning like 3X5 inch mark at asphalt that come from somewhere right behind oil pan. I do not think I have that oil cooler as my oil filter go directly to engine block. And you can see a few drops of oil at that ribbed cable right behind oil pan. Where it come from?

 

My best guess since there's oil along the engine's oil filter side is a leaking front crank seal. Other possibilities are leaking valve covers, upper oil pan, or timing cover o-rings...you could also have a combo of things leaking. For me it was my rear valve covers, and a new gasket fixed it.

 

mine was leaking from the passenger area for a good 2 years, would see small drips every time i parked, it would make a huge puddle of mess overtime and fairly quickly.

The main leak was the timing chain covers, when I was driving it would splatter oil everywhere and of course leak underneath onto the ground after i turned it off.. I never really ran out of oil even when I only drove 3k miles in 10 months..i was trying to avoid driving it too much until I could get it fixed.

so I replaced timing chain covers/all valve cover gaskets/new oil pan/knock sensor/new o-rings/oil pressure switch/new oil/cleaned off all the old oil stains and that stopped the leak. this job was $800, not too bad. the timing chain/rear valve covers take quite some time.