So, I have some basic questions regarding oil in my RX8, and before you tell me to search, I can't find good answers amongst all the threads arguing oil weights. lol

1. When changing oil in an RX8, you supposedly leave 50% of the oil in the coolers and lines. Does this mean you only leave 25% in an auto, which has only one oil cooler?

2. When changing oil, is it okay to leave the old oil in the lines and cooler, or is it necessary to try and drain it by tilting the car?

3. How much oil does the RX8 hold, and should I subtract from that the amount left in the lines and cooler when adding oil after a change?

4. Mazda puts 5w20 in the 8 from the factory, but I want to swap to 5w30. Is it okay to mix oil, or must I drain the cooler completely to change weights?

5. I was raised to check oil when the engine is cold in a piston, yet people say to check the oil in the 8 with every fill up, which means the engine will be hot. So which is it? Hot or cold to check oil?

Straight answers are appreciated. Flaming is not appreciated.

Thanks

Edit: 6. Is it okay to use an aftermarket oil filter like FRAM or another brand, as I read somewhere only Mazda brand filters are safe?

 

1, Irrelevant question, unless you disconnect the oil cooling lines and blow them out with air your not getting any significant amount of oil out.
2, You don't have any option regarding this, Tilting only gets out maybe a pint maybe two thats it.
3, As much as it takes to get it the full line on the dipstick. When I do a change I add 4 quarts then add oil according to the dipstick.
4, Its ok to mix
5, Whichever way makes you happy, the important thing is that the task gets done at least every other fill up.
6, I believe that is only correct for 2009 + models. I have used non Mazda filters on my 04 without issue.

 

1. its there because it wont drain out
2. you can get out as much as possible by tilting the car
3. about 6 quarts total. an oil change needs about 4 - 4.5 quarts depending how much you drained out.
4. yes its ok
5. cold or hot 10 mins after shutting down.
6. Id use Mazda

 

The owner's manual recommendation is to check the oil level when re-fueling.
Text from the manual:

Inspecting Engine Oil Level
1. Be sure the vehicle is on a level
surface.
2. Warm up the engine to normal
operating temperature.
3. Turn it off and wait at least 5 minutes
for the oil to return to the oil pan

This makes good sense for a couple of reasons:

• Engine will be warm by default when re-fueling, which is when most people will check it.
• Considering Mazda's instruction for checking warm, we can conclude the dipstick is calibrated likewise. Checking / adding oil when cold could therefore result in overfill condition when hot.

 

Listen to Expo, Nuff said

 

"Whichever way makes you happy" is not the factory instruction...

 

doenst make sense checking oil on a hill right?
the reason for waiting 10 min is engine is still pretty hot in 5 min.

 

They say to check it at every fill up doesnt mean you have to actually check it at the pumps lol. Hot or cold is fine. You only need to cheack it every other tank or about 600 miles. I find I'm down almost a half a QT at that point.

 

/\ FAIL..

HOT OR COLD is NOT Fine...unless...

To OP...what does the sticker on your Fuse Box cover say??...ONLY CHECK ENGINE OIL AFTER 5 Minutes hot engine turn OFF.

There is a 300 mil (large Cup) of Oil difference between Hot engine oil and Stone Cold engine oil..
if you Fill to the F mark on a stone cold engine you are technically overfilling your Oil pan and Engine.

On Series 2, I ONLY check my oil when engine is stone cold (on car level floor) and MY FULL MARK is about a quarter of an inch (or 5mm) BELOW the factory F mark on Dip Stick.

So when engine is HOT and after 5 minutes turn off my oil is always at the F Mark.

 

Well i guess my car isnt burning any oil then. Cause I check it cold after 600 miles and im always down a quarter inch on the stick. youre telling me its actually full?

 

Thanks mate. This seems like the best answer so far, but thanks to everyone.

 

It is not that hard to see..

Get your car hot, check the Oil after factories recommendation of 5 minutes engine off, so then if it is Full it should be at or on the F mark...correct?

Later the next day when Stone Cold check the oil again, it should be the distance I said (approx) Below the F mark...

 

Oil dipsticks on all internal combustion engines, RX-8 to lawnmowers, are marked for checking when hot. As Pete indicates, if you check cold and add oil you may actually be overfilling.

The manual also indicates 3.7 quarts per change with oil filer change (series I).

Why not just follow the owner's manual? It's written precisely for a purpose! Geesch!!!

 

Well I must have been dong it wrong for the past 40+ and the Techs where I work, after years and overfilling (excpet RX-8)...lol

Every other car I have ever owned I have always checked oil when cold...not this hot, wait 5 minutes bullshit.

 

^ But you're down under - you do everything upside down.

 

for 2009+ RX-8, use Factory oil filter. try to avoid aftermarket ones as much as possible.

the problem is the bypass valve, most aftermarket filters designed to open at around 11-17 psi. but stock opens at a much higher point, was it 22 psi or so I forgot.

if you use aftermarket filters on 2009+ rx-8, the filter will spend most of its time in the "bypass" state, meaning your oil will NOT be filtered most of the time, not good.