I'm running into a conundrum while used car shopping where there are two cars which are the same make and model, similar features, but they differ in miles and model year. In these cases, the older car (usually by about 1-3 years) has lower miles (usually by about 20-40,000 miles). Given that all other features are essentially equal on these cars, which one is likely to be a better buy from a reliability standpoint? More miles obviously equals more mechanical wear, but more time can add corrosion, chemical breakdown, metal fatigue, etc. Is there a point in miles or years where one becomes too much compared with the other? Are there any other factors to consider when comparing cars in this type of scenario?
Example: A 2008 car with 106,000 miles, vs. a 2010 car with 130,000 miles.
Note that I'm not including specific make/model/year here because I have run into this several times, so I'm looking for answers to this problem in general terms, not details about specific cars. For what it's worth, the cars I'm looking at are typically around or above 100k miles already.