I do compression test on my e21 M10 engine 318 (on cold). And these are results cyl1=7.4 bar (110psi); cyl2=cyl3=cyl4= 10 bar (150psi). After that I put some oil in cyl1 and after that he get 10bar (150 psi). Now I'm wondering if someone know what in usually case is damaged , piston rings or cylinder. How much repair cost and can I put standard rings or I must machined cyl ... and buy new piston +0.25 or +0.5. rings and etc.
Briefly is this big problem and should I consider about finding new engine, or repair this one for reasonable price.
Please recommendations and advice what should I do. Can I drive car with this engine or it is not recommended.