Nothing but Dexcool for 12 years now and nary a single problem.
I'm no expert, but GM seems to have an issue with the intake manifolds on the V-6 engines, I think more because the're running EGR through plastic than anything else. The mechanic's guess was not unwarranted, unless he actually looked at the vehicle... Don't see how the bubbles could come from the intake.
So you in-law's logic is that Dexcool made the mechanic stupid?
The Constitution needs to be re-read, not re-written!
If you can't handle Dr. Seuss, how will you handle real life?
Current oil burners: MB GLK250 BlueTEC, John Deere X758
New ride: MB GLS450 - most stately
Gone but not forgotten: '87 F350 7.3, '93 C2500 6.5, '95 K2500 6.5, '06 K2500HD 6.6, '90 MB 350SDL, Kubota 7510