Engine started to blow smoke and engine light game on. Checked oil had sludge on dip stick. I have been going 8000 miles between changes. Has 94000 miles. Took in and they said new engine or they can try to flush sludge. 50-50 chance it will work. Is it worth spending 600 flushing engine? They said that scoping cylinders they look fine. They said compression is ok. Any help would be great!