Three quarts in 1000 miles?? That oil has to be going somewhere. If the engine is leaking that bad, you should see it either on the floor or pooling up in the pan below the engine. It may be dripping out while you're driving..........? Or it could be smoking while you are driving and cannot see it. 3 qts is a lot of oil to just dissappear.

I changed my valve cover seal, got rid of about 97% of my oil leak. The rest is coming from the timing chain cover. Doesn't leak too bad now. I used 1 qt in about 2000 miles, which is OK because it was time to change the oil anyway. My 300E has 195K on her.

Good luck finding where it's all going.