Newbie here with some questions to determine the used Mazda6 I want to buy. Thanks for all your advice, knowledge and expertise.

My currend DD has 320K miles and it could go out at anytime, so I'd like to narrow down my used car search as much as possible. I've determined that I'd like a first generation Mazda6 wagon for a a variety of reasons and I want to know the general reliability and pros and cons of the auto vs manual transmission. I'm leaning towards the manual because it's fun, but manual wagons are hard to find. My wife can't drive stick yet, so there's that...

What reliability issues are there with the v6 engine in the 1st gen, and any reliability issues with the two types of transmissions?

I test drove a manual last month with 140K miles and the clutch was slipping in 2nd and 3rd gear when I punched it at 3000+ rpms. How long does the clutch usually last, driving reasonably?

Any tips of advice would be greatly appreciated of what I need to check on a used Mazda6, thanks in advance, I'm stoked to have a 6 soon, the test drive was fun.

 

The automatic 6 speed tranny by Aisin is not very good unless you install an extra external tranny cooler (I have this in my 2006). The factory cooler in the lower part of the rad is a joke, and people don't change fluid enough on the automatic (every 30,000 miles). READ: Why ATF Wears Out
If you get a V6 in 2006 or 2007 your stock exhaust will cause issues. READ: https://www.mazdaforum.com/forum/maz...-design-28940/ .
Higher mileage cars will require lots of fluid changes: power steering, tranny, coolant, oil. Ignition coils with hi mileage should be changed as well as spark plugs. Clean the throttle body, MAF sensor and EGR. This is pretty standard for all used vehicles.
Mazda never changes the PCV valve so you should change that as well as the hose attached to it.