Oil is cheap, motors are expensive. To me it's cheap insurance. My Z isn't in that boat, but I have some other vehicles that are. I have one that got 62 miles on it last year, it will still get changed this year (actually ordered the oil this week since no one carries it locally). As mentioned if you want to try and stretch it out, the only way to know for sure if it's still doing it's job is to have it analyzed by a lab (thats how I found out Amsoil wouldn't go 8k in my daily driver).
Now for the dangerous part.... haha
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And not to start an oil thread, but you can get five quarts of Mobil One is $25 at Walmart, another quart will run you another $6, a quality WIX filter from the parts store will run $8, plus another few bucks in tax, your still talking $40? Even if you think your current oil is "better" are you driving enough miles to care? Then it's not as much of an ouch on the wallet every year.
Before anyone says
I'm not being brand loyal to Mobil, it's just an example I'm throwing out.