I have a 2008 Avalon (6) and a 2008 Camry (4 cylinder), each with about 60K miles. Both have original transmission fluid and coolant/antifreeze. What is the mileage and/or age I can safely attain before these need to be changed?
There are two factors in determining fluid changes: Miles and time. The miles are not a problem, here. The time is a problem. Both fluids have additives that lubricate and prevent damage. Given what you're communicating (no fluid changes in thirteen years), there's bound to be trouble. I would not be surprised if the transmission seals are hard as rock. And if you want to assess the corrosion level of the coolant, just use a multi-meter and measure the electrolysis. Anything over .3 (red probe in the coolant with the cap off and black grounded on the car) shows that electrolysis is corroding your vehicle.
Likewise, you can use a fish tank pH level strip to determine the level of acidity in your coolant. Anything below 7.5, well, it's time to change the coolant. Below 7, the coolant is acidic and is actively corrode aluminum. The result of the process is aluminum oxide, which is a form of sandpaper circulating between your radiator and your engine.
