HomeAll RepliesReply To: Major oil leak Reply To: Major oil leak Sponsored October 13, 2023 at 7:43 am #783410 trvParticipant Over fill on the oil can cause leakage. It can also blow the main seals in crankcase if pressure rises too much or too fast. Overfilling is never good, unless it’s just a very little bit. 1/2 inch above the full mark is too much. Sponsored Subscribe to GM Authority For around-the-clock GM news coverage We'll send you one email per day with the latest GM news. It's totally free. First Name Last Name Email Address Subscribe via Email Leave this field empty if you're human: Sponsored