Whitish smoke coming out of tailpipe at startup

Hello, I have a big plume of whitish smoke coming out of my car's tail pipe. There is also an oil leak, about one quart every two weeks. The coolant level is stable. The dealership and another mechanic informed me there was a lot of sludge in the engine, and that there is an oil leak. The mechanic has tried to clean the oil out with an oil additive (twice) to lower the sludge, which might help lesson the smoke. It has not worked at all. I do no't want to put too much money into this as it has 85,000 miles, but want something to keep it going for maybe 10,000 more miles. Thanks.