Hello, This regards a 1999 Saab 9-5 2.3 (4 cyl.) with 90K. The Saab blue coolant had been changed at a dealership once before. I cleaned the reservoir bottle for fun and noticed more than superficial filming. There were patches of a thick, firm, jelly-like substance. I know the bottle is a high point where deposits can accumulate. My question is about flushing the system. I have some Prestone flush and was wondering if there's a proven product which is better. Also, What coolant can be substituted for Saab blue coolant? I will flush the system repeatedly, using every chemical known to man, if necessary, until clear. Kira