You should see what's causing that. How hot is the ambient during this stop and go traffic?

 

Thanks for all the info guys. I've been having a lot more froth than usual and this was a good recap of the problem and possible solutions.

 

Anywhere from 40-110.

 

I recently installed the "Ventilation Kit" on my 2004 RX8, part number N3Y1-13-S80A

It looks like it eliminated the mayonnaise on the dip stick...

Also, one reason it was so expensive is that it comes with 3 new solenoids...so if you want to kill 2 birds with one stone you can get the ventilation kit.

 

Here is what the old filler neck / vacuum chamber looked like when I pulled it and replaced it with the upgrade...this is what Mazda was saying is "normal"...unless you complained enough and they would replace it.