I just bought an 04 Mazda6 2.3L with 70k miles. Went to change the oil and found the much talked about filter cap. I have about every oil filter wrench except the special 75.6mm wrench specifically for this engine. The cap isn't budging so I guess I need to buy the wrench right? It is unbelievably tight! Should it be that tight?
Then, I notice a yellow paint mark from the engine onto the cap marking its tightened location. Like I've seen on electronic adjustments you don't ever want turned. Has anyone ever seen this and does anyone know why someone would mark the tightened location of an oil filter cap? This makes me wonder if the cap has been that way since the factory and maybe the filter has never been changed? That would explain why it's so tight. I may contact the previous owner and find out who last changed the oil to ask a few questions. Any ideas out there, let me know. Thanks.

 

Hmmmm? That is strange. I assume you are speaking of the cartridge filter bottom, the black plastic part?
I know that before I converted to the spin-on, mine was always awfully tight too, and I am definitely not one to over tighten oil filters. 1/2 - 2/3rds of a turn is my goal, but the filter housing does have an o-ring that can leak if not tightened correctly too.
I've not seen the yellow paint mark you are referring to, or have just forgotten about it. These housing can be cracked, and the aluminum drain plugs in the bottom of it strips quite easily too.
Do yourself a favor, when you get this problem figured out buy the spin-on conversion kit... the same filter they use on the 2.0L engine. It costs right around $40 w/o a filter, takes 10 mins to install and will save you a lot of aggravation.

 

Yes, cartridge black plastic cap. Is there like a torque spec for this cap? I don't mind it being tight but this is ridiculous. It's like they sealed it permanently and marked it to never remove it.

 

I'm sure there is, as there is on everything, but I couldn't tell you what it would be.
I had tried and failed several times to make mine easier to get off when the time came. I am also convinced that the threads on the housing are tapered, like pipe threads, so the more you turn it in, the tighter it gets. The o-ring still has to seal or it is all for naught.

 

Some info...

 

Thanks for the info. I haven't bought a repair manual yet.

 

You do not need to purchase it - just download archived manual from here and enjoy http://www.mazda-auto.ru/docs/m6-workshop_manual.rar Although it may be for European only the manual is in any case very useful

 

Thanks but I'm not able to open an .rar file. I tried to go to the mazda-auto site but it wasn't in English so couldn't find another format like pdf. Let me know if there is another file type available. Thanks.

 

Sorry, I do not know where it is possible download PDF version. But the file inside the archive is ~ 40 MB PDF. So, just install WinZip or WinRAR on your PC and un-zip. Or, you may extract the manual on another PC where WinZip / WinRAR are already available.

 

Mystery solved! I guess I've been changing my own oil way too long. I told someone about this today and they said "oh yeah, Walmart always marks mine like that" I guess its a liability thing or proof that they did change the filter and left their mark. So no worries. And I got my filter cap wrench in the mail today so hopefully that will do the trick.