1985 Cadillac Eldorado Biaaritz with V-8 FWD. Have a (2nd time) oil leak around rear of oil pan gasket. First one(2002) cost $1500 due to needed removal/lifting of engine to allow oil pan to be removed. Different mechanic(from first repair) says recurrence of leak is due to flange of original oil pan being too thin for torque bolt specs. Says the recommended torquing of bolts causes bending of flange and viola! even a new gasket is deformed and cracks prematurely. He recomends that I get an aftermarket oil pan with beefier flanges before undertaking a second ($1500)repair to prevent leak from recurring. He said the GM people simply under-engineered the thickness of the oil pan flanges for the stresses involved in the bolt areas and also states that the FWD configuration adds a lot of vibration stress to the oil seals. Any advice on aftermarket oil pan suppliers for a better oil pan than original equipment? Would it require other modiications or just the better replacement pan?
Fel Pro makes an improved gasket set for the 4.1 / 4.5 / 4.9 Caddy V8s. If you hit up http://www.summitracing.com and look up part number FEL-OS30525T. It’s a $37 kit, but it’s supposed to be a big improvement over the standard cork or rubber gasket.
Maybe the bolts came loose. Be sure that you are using the right weight oil too. The 4.1 engine in the sedan de-ville that year took straight 30 wt where temps didn’t get below +30F. Some places just dump 5w30 in there. Guaranteed to leak if thicker oil is required.
Is the mechanic who is saying this stuff the same guy who did the first go-around with it? If so, I really question some of that garbage he is telling you.
Many pans have thin flanges, and have had for many years. It’s not a problem unless the pan and gasket installer allows it to be. That is usually spelled “ham fisted”. It’s a mechanic problem, not a pan one.
FWD configuration adds vibration stress to oil seals, huh? 
Bunk.
Raising the engine or not, this is not a 1500 dollar job. I think you done been had. (grammar not corrected)
My guess is that if it’s the same guy here, he neglected to check, and straighten as necessary, the oil pan flanges the first time. It may have then been followed up with overtightening the pan bolts.
If a cork gasket is used then it’s possible to crush or cut the gasket by overtightening the bolts.
Try tightening the pan screws (gently). Check the book value of this car before you spend another $1500 on it…