I have a car with dex-cool (Buick Century 2002 3.1 V6). The car has been driven very little and has only 15K miles on it. Not a typo, that's fifteen thousand miles in a 2002.
No work has been done recently. No engine work ever, AFAIK.
Last fall I noticed that my mileage had dropped from 23/33 to 14/27 mpg.
Last week, I lifted the hood to see if I could spot any loose or broken vacuum lines, and I noticed that the lid of the coolant reservoir was off. The reservoir was empty - I don't know if it had evaporated out the top, or if there is a leak.
I have good power when I step on the gas. No odd noises. I haven't spotted any leak. But I'm in the northeast and haven't been looking much, seeing as how it's winter.
I just became aware of how dexcool can cause the Lower Intake Manifold gasket to fail, and the now-expired class action suit. I don't suppose there's any way to know what percent of 2002 Century will fail.
And btw, how do I get the LIM checked? Would any mechanic have a simple/easy check that they would do for free? Thanks.