Hello guys,
Wondering anyone who can help me with this. Got my 8 jsut couple days ago. The dealer use Castrol 20W-50 grade mineral oil for the engine. I am located in Singapore. I have a question here (probably sounding like an idiot ): Is it ok if I top up with same grade of oil but synthetic ? Or it is better to stay with the same oil for topping up.

 

I don't think that Synthetic and natural oils will mix. You should stick with the mineral oils. I'm not going to open this up to the synthetic or not synthetic debate, but whatever you use, it should be the same. Do not mix synthetic with natural oil.

 

Thank you for your in-put. Will do just that. Although I love this baby but I had never paid so much for a car that need this much pampering.......

My old 150bhp civic was virtually maintenance free on my part. Just need to send it in faithfully to the dealer for servicing. For 5 years - no problem.

 

The dealer used 20w50!!!!!!

In the US, the recommendation is 5w20, and I've read that other parts of the world get a 10w30 recommendation. However 20w50 is probably WAY too heavy of an oil for this engine. The thicker oil will build oil pressure easier, but the oil flow will be much lower than the designers intended for the bearing clearances in the engine. Also, and potentially more of a problem, the 20w50 probably won't result in the same amount of oil injection to lubricate the apex seals.

Of course, if Mazda recommends 20w50 for your area based on climate, etc., then disregard this. However, I'd thoroughly check this out to avoid potentially shortening the life of your engine due to insufficient lubrication.

 

Hey W2,
Thanks but the weather here has 2 seasons. HOT and HOTTER. Today it was 35C outside. Engine cooling is a problem. Been doing search in this forum and found that 20W-50 is probably more ideal for hot enviroment and if you are into racing...... (well, I like think I am......first one off the traffic junction....ya baby ya baby)
5W 20 is not the best oil for the engine but it has very low viscosity and does reduce fuel consumption a little (according to the article I had read somewhere here) but more importantly, the reason this grade of oil is recommended by Mazda has to the with the US Government regulation that the car has to be energy efficient ......can't remember the exact wording I had read but hey. do a search in this tech garage, you should come across some helpful articles.....

Thanks AGAIN. How is your baby doing?

 

Quick, call all the oil manufacturers selling synthetic blend oils, tell them to STOP!!!



Seriously, all the synthetics marketed these days are fully compatible with mineral oils, and can be mixed to your heart's content. It's not a great plan because of different additive packages to the oil, but it won't cause any problems at all.

Regards,
Gordon

 

I didn't know that. Thanks for the info! I had read (or remember reading) that they were immiscible.

I retract my last statement.

 

I saw your location, that's why I prefaced my statements with a comment about climate/location. There are at least two factors that have lead to increased recommendations for lighter weight oils in the US: One is certainly due to the manufacturers trying to eek out the last smidgen of mileage.

However, the other is the fact that today's bearing clearances are tighter and better controlled. These tighter clearances require a thinner oil to get the same flow that heavier oils in yesterday's engines would give. Oil flow is as important as pressure, as it carries away debris and heat. If the oil is too heavy, the flow rate at a given pressure will be lower, and it won't be as effective at cooling the bearing surfaces (yes, oil is an important part of heat management).

That being said, I understand your point of view. My only concern would be that maybe 20w50 is a little too much, even for your location. Maybe a 10w30 (as is recommended for tropical areas by Mazda), or maybe 10w40 is a better choice. If it were me in your area, I'd seek the advice of local Mazda rotary expertise...

Happy Rotoring!

 

New Ford V-8's are recommending 5w-20 now also.

Yes all synthetics you can buy off the shelf are mixable with dino stuff. Which leaves this question.... Do they add something to it so they can inter-mix, or are the synthetics based off of dino oil itself?

100% true synthetic oil will not inter-mix with dino oil. Take jet engine oil for example. It's a 30w 100% synthetic oil. It is not compatible with dino oil at all. Not even in the slightest bit.

 

Does this mean I can retract my previos retraction???

 

Can someone just go and buy some synthetic and mineral and mix them to see if they separate after a few days? (I am stingy)

 

Nope. Jet oil and automotive oil are blended completely differently - there's nothing in common beyond the base stock. Automotive synthetic oils are completely, 100% compatible with automotive mineral oils. No need to do any separation tests!

Regards,
Gordon

 

The car has 5w-20 as per manual. If car companies use this to lower CAFE, can I top off with 5w-30? I beleive that 5w-30 is used in other markets. Mixing the two can't hurt, can it?

 

This is why I always bring this point up. Yes, they are made differently. But oil companys boast that their automotive oil is 100% synthetic. How can it be 100% synthetic and not seperate from dino oil?

I am NOT trying to start a heated debate here. So please, don't get that impression.

 

there are 2 different types of synthetics... PAO (polyalphanaolefins) and PAG (polyaphaglycol)


all synthetic motor oils out are PAO synthetics which when it comes down to it are just perfect regular old oil molecule strands - the same as dino except without ANY impurities. They mix perfectly well and exhibit all the traits of regular oil except enhaced alot because they are more predictable/consistant because of the lack of impurities. The only area they suffer is in foam tendencies because in this case you actually need impurities to help break the surface tension on a bubble-so syntheitcs have more anti-foam additives (silicon) and people go crazy when they get their oils tested and see a whole bunch of silicon in the oil and think their air filter isn't working.... but thats another issue all together


There are some PAG synthetics out there in the gear oil market and I wouldn't doubt some select high forms of racing. PAG's are glycol based, kick a PAO's ****, exhibit a long list of desirable traits like complete resistance to fuel dilution, but are extremely expensive and if somebody would accidently mix the PAG with a PAO/dino oil that person would be buying a new piece of equipment because the two types of oils do not mix at all and form all kinds of nasty things.

 

Since the RX8 burns some oil to run... is it good to put a synthetic into the engine? Dealer said make sure you dont do that...

I am not sure... just asking

 

the synthetic in a rotary debate has been going on since the beginning of time.... as for my stance, well I just dumped a quart of synthetic in mine.

 

Isn't semi-synthetic motor oil a blend of synthetic and mineral oil? Wouldn't that mean that the two are compatible?