My 56 Victoria with a 292 has the large size drain plug on the oil pan, I think 1 1/16 or 1 1/8. I have been putting up with the quarter size marks on my driveway and have wondered if modern oils now go where the old oils didn't. I have tried replacing the copper washer with a neopreme one and when that still leaked,  I tried a red silicon sealer smeared on the neopreme washer. It still leaks . Can anyone tell me if they have found a good fix for this?