have just purchased a mazda rx8 evolve ltd edit 06 plate 30000 on the clock when i was topping up the oil and had the dip stick out i noticed the oil on the stick looked as it had emulsified were it was a creamy coulour i then took off the raidiator cap to check it and the cap was spotless just to see if the water and oil were mixing together in case ther was a problem with the cylinder head , i would be more than grateful for any advice you could put to me just to put my mind at rest.

Asked by Dec 31, 2013 at 06:41 PM about the 2006 Mazda RX-8 6-speed

Question type: General

when checking oil i noticed when i had the dip stick out the oil on the stick was a creamy coulor, checked radiator cap which was ok, any ideas why this is?

11 Answers


Check the crankcase ventilation system (aka PCV system). Replace the PCV valve and inspect the PCV hoses for damage, clogs, cracks, or being misrouted. This will sometimes cause the milky" goop" on the oil dipstick as well as on the underside of the oil filler cap and even in the air cleaner. HTH. -Jim

1 out of 1 people think this is helpful.

Change the oil and filter, make sure the PCV system is operational and the oil cooler is not leaking coolant internally, then watch the oil color closely, if it changes to a milky color rather quickly then you need to get ready to replace the engine, as this is a rotary engine it does not have a so called cylinder head. You will find that most shops won't work on these engines unless you find a rotary speed shop. I would recommend you get book on rotaries, forget everything about conventional engines while you are working on a rotary and remember they are 2 stroke by design so they do use oil. Sorry I can't put your mind to rest about your problem

thanks guys much appreciated i will get this checked out asap


You're welcome. Glad to help. - Jim

Richard Boettger

I'll be the first to admit I know little about the rotary engines. But In general, modern cars don't have PCV 'valves,' but an orifice inside a hose that can be cleaned. Use a small wire, carb cleaner or even a welder tip cleaner to force out the gunk. With that many miles on a rotary, I might also check intake manifold vacuum. From my understanding, these engine are extremely sensitive to regular maintenance and if not done, go downhill pretty quickly. Unless you have a full history on the car, assume the previous owner didn't do services as they should have been done.

thanks for answer to my querry Richard very much appreciated like yourself i know very little about rotary engines but i will be in contact with the garage before the w/end to see what they have to say about the problem

Richard Boettger

You're welcome. It sounded to me like you are experiencing condensation in the oil, not coolant. This would certainly indicate a problem within the PCV system. Don't let the shop rip you off, and hopefully you got some kind of used car warranty on this car. Based on the owners I've talked to, and owners post I have read, if you don't know about the rotary and its maintenance needs, you'd be wise to learn. Or expect to pay a lot to a shop to carry them out for you, and that can be costly and dangerous. They are much more delicate than you might think. Think '60's/'70's British sports car... say an XK E-Type for example.

1 out of 1 people think this is helpful.

I use to run the s*** out of the rotaries in my hotrod days, I've flipped rotors, hogged out cases, tired different carbs, headers, basically made them a wide open throttle engines, after blowing up a few I started putting a rev limiter and set it to 10 grand and that made my engines last a lot longer, as I see yours is an 06 so it no doubt already has a factory rev limiter built in, but if you maintain these little engines as stated in the manuals they will last just as long as a conventional engine, if you go and start hot rodding the life drops but you will be surprised on just how much they can handle.

my rx8 looks and performs very well and for an 06 plate it has only 30000 on the clock so hopefully this prob is not going to be to dificult to sort but i will get it checked out just in case, thanks again for all the advice its very much appreciated.


Usually a pressure test of the cooling system will tell you if the system is "air tight" Check harbor freight for the tool. or Call a local radiator shop, cooling systems are all relatively the same rotary or not.

thanks for the info will get it checked

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