I know this question has probably been asked a thousand times, I would just like an answer specifically tailored for me. Be nice!

I'm about to do an oil change and I was thinking of trying the idemitsu oils, but they don't offer them in 5w 20 like the manual suggests. I live in Michigan so I'm not sure how the weather would affect a higher viscosity oil like the 30 and 20w 50 that the idemitsu is.

I'm thinking about just playing it safe and going with Mobil 1 full synthetic 5w 20..

Any help would be appreciated , my car has around 43k and pulls hard like new.

 

search the forums. 5w20 is not what you want in your engine if you care about longevity. Actually the oil threads recently got bumped to the top.

 

Hmm so should I just go with the idemitsu... There's so many opinions on oil, I frequently change mine, so really my only question is how will that high weight idemitsu impact my longevity and performance

 

I remember reading that the idemitsu stuff - I believe it was their "race synthetic" but not sure on that - has a high content of molybdenum-containing friction modifiers. This is obviously very good in terms of lubrication, however molybdenum compounds have issues with solubility, and there is a potential risk that this can cause problems if they precipitate out into solid particles. This is something you want to check before buying it.

The general recommendations around here are to go for a FULL synthetic in 5W-30. Your options for a TRUE full synthetic oil are limited to redline, royal purple and SOME mobile 1 (so check the bottle before you buy it to make sure your getting a true synthetic).

EDIT: As you your longevity and performance question - this is my understanding (which may or may not be 100% correct). The e-shaft bearings are in a very high shear environment and high heat - similar to what is seen in diesel engines. The higher weight provides a better lubricating film between parts than the lower weights under these extreme conditions. You can go through some of the threads of engine rebuild (which is what I've been going through recently) looking at the pictures. What you will notice is that people who run higher weight oils have less visible wear on this part of the engine (however, it is noteworthy that the side seals/apex seals are a far more common point of engine failure than excessive e-shaft bearing wear, but it has still happened). Mazda recommends 5W-30 for everywhere EXCEPT the North American market - so you do the math on that one and think about how various emissions and fuel economy regulations are in different parts of the world and come to your own conclusion as to why mazda chose 5W-20 for the US and 5W-30 everywhere else.

 

are you located in the USA? if so, honestly, grab yourself Mobil1 0w-40.