I couldn't find anything on this on the forum so I thought I'd try to get some answers from the knowledgeable people here.

I have a problem,
I bought my RX-8 a week ago from a private party and the guy couldn't remember what type of oil he put in it. The only thing he could tell me was that he never used synthetic. So I have some Castrol GTX 5W-30 dino and my oil is ready for a top off. Let's just say for all intents and purposes he put 5W-20 in the car previously. Would it be bad to add a quart or so of 5W-30? I really have no idea what kind of oil is in there now.

 

No its not bad.

 

5W30 is fine.

....and your signature picture is way oversized, the limit is 20k.


S

 

if you are that concerned, change the oil.

 

Don't mix synthetic and dino.

your of to mix dino

 

Does he even remember the last time he changed his oil. If he doesn't know what kind of oil, maybe he's forgotten because it was so long ago, or maybe he just doesn't care enough about oil to remember to change it.

 

He did care about the oil he had all the oil changes and service done at a local Mazda dealer... with reciepts to prove it. Maybe it will say on those. The sticker on the window says it isn't due for an oil change for another 1,000+ miles

 

No problem. For the most part you can mix brands and weights of oil. If you mix weights, you get something in between the two. When you change the oil in an RX-8, you usually only get about 2/3 of it out. So even if you do a full change you're still mixing with what was in there. FWIW, even believers in 5w20 generally see no problem with using 5w30.

I agree with Robrecht that if the guy does not remember what kind of oil he used he may not even remember when he changed it last. I recommend getting it changed and embarking on a regular schedule.

Search/browse the forum for the definitive answer on the one kind of oil that should be used.

Ken

 

I don't know the answer to your question, but I know that you were trying to say "For all intents and purposes"....

 

That's very good to know when buying a used car. Would be even better to know that he topped it off every 1,000 miles or so but if he didn't drive the crap out of the car, not to worry too much. (If you live in the US, chances are very good the Mazda dealer used 5w-20 nonsynthetic.)

 

same thing happened to me when i got mine...ust changed it when it got down on the stick figured it can't hurt!!!

 

The Fix,
Let you Car sit for the night. In the morning change the Oil and flush it with 2 extra qts. Then fill it up. Dont over fill and your good
-Gil

 

mixing weight/oil doesnt matter.

Its like mixing colors, if you mix yellow and blue, you will get green. if u put more yellow than blue, u will get light green.

if u put more 5w30 than 5w20, u might get something like 5w28 in the end.

so no biggie.

but like the others have said, if the previous owner doesnt even remember what oil it had, then I suggest you to do a change right away.

 

And use Castro its da bests lol