I want to do a uoa on my oil to see how it is performing. Car has 72,000 miles and I feel I should change the spark plugs. I have never done a uoa. Will this skew the results? Oil has only 1K now. Should I wait after next change or will any contamination be obvious or minimal?? I'm wanting a good uoa on Mobil 1 10W-30 to include bother Winter and moderate conditions. I just don't want the results skewed by routine maintenance.