Just to be clear, there are two distinct methods for checking the oil level on a C7. One is for the wet sump, base models, and the other is for the dry sump, ZR1, Z06, GS and Z51. The procedure described by KLinNBC is correct for the dry sump system. The correct procedure for the wet sump system, which is what the OP has and as per the Owner's Manual, is as follows:
" To get an accurate reading, park the vehicle on level ground. Check the engine oil level after the engine has been off for at least two hours. Checking the engine oil level on steep grades or too soon after engine shutoff can result in incorrect readings. Accuracy improves when checking a cold engine prior to starting. Remove the dipstick and check the level.
If unable to wait two hours, the engine must be off for at least 15 minutes if the engine is warm, or at least 30 minutes if the engine is not warm. Pull out the dipstick, wipe it with a clean paper towel or cloth, then push it back in all the way. Remove it again, keeping the tip down, and check the level ".
As for the situation that the OP has experience, I genuinely hope I'm wrong, but it sounds like it could be an AFM valve or lifter failure. Given that the problem occurred when selecting "Eco", the only mode that will activate AFM on the M7, it is one possible explanation. Another possibility is a broken valve spring but this is unlikely as that should show signs regardless of drive mode. Again, I really hope I'm wrong and that, whatever the problem, the dealer comes good for the repair.
Good luck
Ross
