Volvo Repair: 1988 740GLE Volvo oil leak, ultraviolet light bulb, valve seals

Question
-------------------------
Followup To
Question -
Hi I have a oil leak and it only leaks when it's being driven and then it lets out a whole bunch of oil and we don't know how to pin point where it is coming from I know it is not coming from the filter can you help us it is a great running car it passed emissions and runs very good otherwise. We don't have alot of money so the cheapest way will be our best bet. Thank you and any help you can offer will be greatly appreciated.
Answer -
Hello Garnet,unlike life,with oil leaks,start at the top.oil fill cap seal.it should be bendable without spliting.You sounded too confident that it is not the oil filter, beware aftermarket filters sometimes leave their gasket attached to the engine.To pinpoint the area,clean affected area well.Check oil level,add if its low,spread some paper under the engine/trans area.Start engine and watch.turn off engine and write me back! thank you

Hello Patrick the leak doesn't happen until we drive it at driving speed of anywhere from 25-75 there is no oil leaking around the oil filter and its clean and when the car sets the oil level stays full until we drive it.  Thanks Garnet

Answer
Hello Garnet,  Well so much oil needs to leave a trace,so a visit to your local parts house and get some 'engine oil dye'.There are different ones for other systems.Yellow glasses and a ultraviolet light bulb will be needed to lite up the dye.The only other likly place is out the exhaust.Oil getting passed valve seals,piston rings.At high speeds that engine is breathing like a train and the result will be 'oil useage',Ah.. the plot thickens. We need physical evidence,to that end we employ the dye.Also have a friend trail you for the next road test.To be continued!  PKD