I also do my own changes, and have developed a way of checking the oil that I feel offsets the disparities the crummy dipstick seems prone to. I always check in the a.m., in my garage, and the car's usually been sitting cold for at least 8hrs. I also get inconsistent readings, but have found that by wiping the dipstick thoroughly, letting it sit in the pan for 2-3 seconds, and taking 3-4 measurements gives me a real good idea where I stand w/oil levels. Once I get a consistent reading I stop and add as necessary. I recall someone else taking a file and scratching some lines in a X pattern across the dipstick where the "L" and "F" are, in order to get more consistent readings....IIRC they had good luck with that fix.