Since I purchased my 89 745 TIC several years ago, I had been plagued with sudden oil losses. Various remedies included a check valve in the small line from the intake manifold to the "Y" on the breather connection. I have finally had a chance to test the latest remedy and this will be my final report. As much as I would like to credit my ingenious check valve fix, I must report that in the final analysis the problem was a bad main oil seal. It seems my erstwhile ex-mechanic (Taylor Motors, Mooresville, NC) neglected to include the lip sealing spring when he installed a new oil seal in a rebuilt engine. Finally after numerous carport puddles and using a quart every 750-1500 miles, I resolved to change it myself. It's a fun job so why trust Taylor when they got it wrong the first time? I used the upgraded tan colored seal from FCP Groton which is thinner so as to relocate the lip on the crank (which showed no wear) as well as being of tougher material. I have done about 5K miles since the new installation (including one oil change) and have not lost a bit of oil. Last week I towed a trailer from NC to NJ up I-77,81,&78 and returned with an 800# Gravely on board. The return trip was done @70mph with the OD locked out turning about 3700rpm. Whereas the grades around Christianburg,VA used to consume a quart of oil in ten miles, there is now absolutely no oil loss with 212K miles on the car. I did have a distributor rotor disinegrate near Christianburg (from the heat I guess) but that is a story for another day.