I'm a DIY'er and have performed all regular maintenance on every car I ever owned when possible. I know what I'm doing. My wife took her '06 GS300 to the dealer today to have the tires rotated (I have a back injury and can't do it myself for a while) and while she was there they tried to sell her an oil change and she told the guy that her husband (me) does all that already. Then he rolled out the "you know that will void the warranty" speech. This is not the first time she's heard this as she also heard it once when she had her ES300 back in the day. Is there really something to this or is this just the usual dealer scare tactic?
ps. she did have the first oil change done at the dealer but all subsequent changes are done by me. This has been the practice in my family forever.