Approximately 4 months ago I installed oil separators on both my 2003 and 2015 Honda Civics. Both installations are on You Tube along with one on my 2018 Ford F-150 5.0. I was told it was a waste of time especially for the 2015 Honda since there was a device in the engine design so oil vapors in the intake would not be present. I'm going in for and oil change in the morning (coupon at selling dealer) and decided to look. I had only checked once after about a week after installing and found nothing. To my surprise there was about a table spoon of oil in the container so I glad I installed it.

Here in Calif it is against at the law to tamper or alter an emissions device and when I go for my smog check I'll place the original hose on so it will pass visual like I will on all my "altered" vehicles.

I've looked in intake manifolds on both direct and port injected engines and everyone has had oil contamination on the runners. There is no fuel to mix with the blow-by oil vapor like carburated cars of the past and with the way my wife and both short trip city drive I'm glad I have them.