I'm trying to help my brother. He has a 1991 Subaru Loyale that is leaking oil. Could he switch to a thicker oil to slow the leak? If so, how thick can he go, it only has a 1.4L 4cyl motor? Or, is their an oil or additive you could suggest that might swell the gasket/seal so that the leak stops. Fixing it is out of the question. Simply not worth the money. It's a pos. Also, it is leaking a quart every other week, maybe a quart every 3 weeks.