manuRx8

Hi all,

Although the best way to change the oil in an Rx8 is a subject already treated, it is always in the air to extract the oil from the coolers.

The method of tilting the car left and right helps to extract the oil remaining in the ducts, but it does not manage to eliminate the liter of oil that is retained in the coolers.

The most radical solution would be to release the thermostats from the coolers, but it is delicate, cumbersome and in the long run could cause leakage and loss.

I think I have found the simplest solution to this problem. It had been a while and yesterday, I had to change the oil, I took the opportunity to try it and it works wonders.

With the hot car, you start a normal (and homemade) oil change by lifting the car from the right front side (with the jack), put on a safety stand, put the tray to collect the oil and remove the plug from the oil pan.

While it is emptying, remove the oil filter (I always change it with the oil).

Now the good starts:

You take a rubber tube with an outer diameter of 12mm (eg a gasoline tube) and fit it into the small hole in the oil filter base (to the left of the central hole)



(That hole is the return circuit of the oil coolers)

Then connect the other end of the tube with an air compressor (the compressor to inflate the wheels) and have it blowing for a while (1 or 2 minutes are enough). The air that enters goes directly to the radiators, pushing the oil contained in them and causing it to be discharged into the oil pan on the same circuit through which it had entered.



To ensure that all the ducts are as empty as possible, we change the jack on the left side (as is usually done in a conventional change) and while we wait for the rest of the oil to drain, we blow again.

Once it stops dripping, we change the jack on the right side (and put the safety trestle), put a new gasket on the oil pan plug and screw it back into place.

Finally we remove the blow pipe, fill the new oil filter with clean oil, moisten with oil your gasket and thread and put the filter (remember to tighten it only by hand)

Now we fill the engine with the new oil and we already have an oil change for a season.

IMPORTANT: Before starting the engine, remember to activate the starter 3 or 4 times (about 10 seconds) and always with the accelerator pedal fully (to prevent the engine from starting). This ensures that the ducts (and coolers) are filled with oil, thus preventing the engine from running without oil in the first instants.

If you are curious to see how much oil is removed from the coolers, you can do the maneuver in 2 steps. Before applying air, wait until the oil stops dripping, change the container or tray where you collect the oil for a clean container. Now you can blow and see how another liter of oil comes out, which means that the coolers are practically empty of oil.

In addition to how clean and simple it is, what I like most about this system is that the time needed to make the oil change is the same as that of a simple change, since the blowing operation is done while you are waiting to empty the crankcase completely.

Do you like it? Did anyone know a similar method?

Steve Dallas

Great write-up, but this is completely unnecessary. Just do a drain and fill every 3K miles (filter every 6K miles), and the oil will be fresh and clean enough.

Also, have you thought about the potential momentary drop in oil pressure you are inducing by removing all of the oil from the system? You may be doing more harm than good.

NotAPreppie

I pulled my oil coolers and lines to inspect them for rust the last time I pulled my motor. IIRC, I only found maybe another 1 qt of oil in the whole cooler system when I did that.

I doubt there's anything wrong with doing what you're doing but I don't know if it's worth the effort. Just keep a reasonable OCI and you'll be fine.

manuRx8

I drive this car about 12,000 km a year (7400 miles), that is, I should change the oil 2 or 3 times a year and the filter at least once.

If I do it myself I only lose time, but if I send it to a workshop, I also lose my money. In addition there is the price of oil plus filter, minimum 70 € ($ 78).

With the system that I propose, which makes me lose only 1 or 2 minutes per change, I save the labor of at least one oil change and just over € 30 ($ 33) in spare parts and oil.

You know what I'm telling you, that at least to me, the solution you propose is not profitable to me.

Relative to the pressure drop to remove "all" the oil, it seems that you forget that the oil ducts are going to empty the same, remove or not the oil from the coolers and that is why you should take the precaution of turning the starter several times, with the accelerator pedal fully, to ensure that the ducts (and the cooler if it has been emptied) are filled before proceeding to the normal start of the engine and I repeat, it must be done regardless of whether it has been emptied or not the coolers.

manuRx8

The exact volumes according to Mazda are:
3.3 ls (3.487 qt) in engine
0.2 ls (0.221 qt) in filter
1.2 ls (1.268 qt) in coolers
In other words, an oil change without coolers leaves 25% of old oil in the circuit.
it's up to you...

NotAPreppie

The total capacity of the system (filled from dry) with 2 oil coolers is 7.1 qt. An oil+filter replacement should be 3.7 qt when using the drain plug.
ENGINE OIL REPLACEMENT

I usually get 4.5 qt using an oil extractor without going through any extra acrobatics to lift one side of the car up or blowing air through the system.

UnknownJinX

And would this work for S2 with the different location of the oil filter?

This isn't a terrible idea... But I don't have access to a compressor(unless you count the emergency one for flat tire in the trunk) so for me, it's added cost to invest in one.

I have 2 UOA reports also showing me that a normal drain and fill every 3k is adequate.

For an S2, I think a good drain and fill with filter gets about 4.4 L/4.6ish US qt out, and the entire system holds 7 L/7.4 US qt for a MT. AT models have only one oil cooler and holds 6.3 L/6.6 US qt out, so there is about 1.4 L/1.6 US qt in the oil coolers in the S2.

manuRx8

The compressor that I used is one for flat tire, similar to the one we carry in the trunk.

If you use mineral oil, the change every 3k would be acceptable, but using synthetics it seems to me that it is wasting oil.

UnknownJinX

I think a few people run synthetic and change every 5k miles without draining the oil cooler, and they still do okay according to their UOA.

They said to crank, but not start the car to prime the system, so the lower oil pressure shouldn't be a concern.