Hey guys,

My wife accidentally added a quart of synthetic oil to our 2004 rx-8. Prior to that it has always had non synthetic. I didn't find this out until just now. She added it about a week ago. What 's happening is when the engine is cold it runs great even when the temp needle is at the mid range (normal) position but about 10 minutes after that the car seems to loose all power idles too low and will die at a stop light if the a/c is on.

I have no clue what to do except change the oil asap. My question is.... is the engine ruined, or do you think there is some other problem and it's just a coincidence? Can I recover from this?

Will changing the oil fix this?

Please help.

Thanks!

 

I highly doubt the oil mix-up is related to the issues you are experiencing. I will not speculate, but I am sure some veterans will chime in to help point you in the right direction.

 

You now need to rebuild your motor sorry

 

year? how many miles? .... sounds like engine is done .... under warranty ..??

 

When did the last time you've replaced the plugs, wires, and coils?

 

You have absolutely nothing to worry about, at least as far as the oil in your engine is concerned. You can freely mix synthetic and dino with no ill effects. Even if you solely use non-synthetic, adding a quart by mistake is no big deal. It's nothing.

 

Just don't tell the dealership... Your wife did good ... you should thank her for giving your 8 some good ol' healthy synth.

 

I appreciate all the inputs from everyone very much. Now I'm confused. motor bad or good?


Anyway, the coils and plugs are new. wires... not so new , the engine was replaced by Mazda under warranty at 78k due to compression issues it now has 106k.

Regarding the wires, any ideas where to get a not too expensive set? Also, It seems if the wires were going bad, wouldn't the performance be consistently bad or is there a difference when the engine is hot. sorry if this is a stupid question.

 

Check your CAT

 

How do I check the CAT?

 

Sounds to me like it could be your CAT but I'd replace those wires as well since you have 106k miles and still haven't replaced them...

 

Mixing in one quart of synthetic oil for a week isn't going to harm anything, and certainly isn't the cause of your concerns.

As for the catalytic converter... A restricted exhaust could certainly cause power issues, but not idle issues (unless it was a catastrophic failure, in which the engine wouldn't be able to accelerate at all.)

I would start with cleaning the Mass Air Flow sensor and the Eccentric Shaft Position sensor.

How "new" are the coils and plugs?

 

Thanks for your help!! the coils and plugs have less than 3k on them

 

Dude,sorry I hope I didn't get your heart rate going to much.
Just hoping you would've done a little for searching before posting. You gave us no info about your car at all

 

Not like this.

 

also check MAF sensor and clean.

 

Pointless post, misleading post, good information, repeat...

Mazmart would be your best bet for wires me thinks! Wish the wife would change my oil lol

 

Advance Auto Parts has OEM style NGK wires for $30-ish.

 

clean MAF, change the coils, plugs, and plug wires then re-evaluate
then hug your wife for putting proper oil in your 8

 

Stop blaming your wife man. You put that oil in there. It's ok to admit that, haha.

 

As was mentioned Wires, clean the MAF sensor (be careful and use MAF spray). Check the Air Filter. Hows your mileage?

 

My mileage was getting pretty bad. Then I recently reset the ecm thinking it might fix this problem and it looks like I'm getting better gas mileage now.

Thanks for all the advice! You guys are awesome!

Nice to have a place to turn to instead of paying a dealer $$$$ for something I can do. Still need to know how to check the CAT if someone can explain. I checked the threads, but there really isn't much detail. Does anyone have any links?

Thanks!

 

okay, i think everyone missed the most important first question.

when you say she added 1 quart, are you talking like she topped it up with 1 quart? If so, she could've over filled the oil. Check your intake(take out your air filter look down that pipe), you might have oil being dumped into your intake/throttle body area which could gum things up. IF you own a 04-05 and don't have a oil catch can that is what happens if you over fill the oil.


if that is the case, oil change, and clean out your intake as best as possible, there is a DIY throttle body cleaning thread somewhere on here, also use electrical spray cleaner and clean your MAF.

 

https://www.rx8club.com/series-i-do-yourself-forum-73/diy-oil-catch-can-install-basic-164463/


read ^^^^

Step 1: Do you need a catch can?
In the 04 and 05 models, if you overfilled the oil, it could blow back into your upper intake clogging the throttle body and perhaps causing your SSV valve to be stick closed. (bad, causes stalling at Idle, build up, etc)
A catch can will keep all of this oil "blow by" of overfilled oil out of your intake.

 

to check the cat you must remove the mid pipe from the car. You can then look inside the pipe to check the condition of the CAT.

If it looks clogged up or cracked like this



Then you need to replace it.

If it looks like it is maintaining a good free flowing honey comb like this



then its good to go