Superfan

Nearly half of the old oil is left behind in the oil coolers, rotors, etc that doesn't drain into the sump. This concerns me to the point that I might disconnect the oil coolers and drain them along with what's in the sump. It might be alright to drain the coolers every once in a while but draining them on every oil change could result in damaging a cooler by accident. I haven't checked the oil coolers plumbing but it might be possible to get some extra oil to drain into the sump by jacking the car up and letting it drain over night. Have any of you guys checked for drain plugs on the coolers (like a radiators drain plug) or come up with a simpler solution to this problem?

CWB

iTrader: (1)

I would feel better just doing another oil change a couple days later to get the old to new ratio of oil to a more exceptable level. I also like to pour a quart into the top while the plug is out to flush a little more old oil out. The down side of draining the coolers is is you would be letting air into the lines that would have to get pushed out and prolong the low oil press after the change. The only way I would change the oil on the coolers is it you flushed them with good oil under very low pressure like a steering rack...

wakeech

if it could work, that might be a brilliant idea: go for a good drive, get the oil hot, drain 'er all out with the nose up in the air... could work .

Quick_lude

Ok this somehow doesn't make very much sense to me.. If there is 3-4 litres of old oil "stuck" in the oil coolers, do they get recirculated into the system with the new oil? Or is the oil cooler oil and oil in the oil pan on two seperate systems? Becuase if the cooler oil is recirculated as soon as you start the car up then in reality you will never have clean oil in the system. Am I missing something?

Superfan

About 50% of the oil is left behind. Even if you change the oil again a few days later, your still going to have about 25% of the old oil mixed in with the new. Pouring a quart of oil in while it's draining isn't going to do much either. It's just going to go straight into the sump nad out the drain hole.

Quick_lude

If that's the case, how does that make any sense? You will always have 4L of old used up oil mixed with the new stuff? How is that good for the engine?

notdeafyet

The engine's oil capacity is 6.7 quarts. So, if 50% is stuck in the coolers when you drain, then your first change results in:

50% old, 50% new (don't change the filter yet)

Repeat the next weekend:
25% old, 75% new

Repeat the next weekend and change the filter:
12.5% old, 87.5% new -- this is good enough for me.

Each time you drain 6.7/2 = 3.35 quarts

The hassle is revisting the darn procedure and wasting some of the new oil:
The 2nd change wastes (.5)(3.35) = 1.675 quarts of new oil
The 3rd change wastes (.75)(3.35) = 2.5125 quarts of new oil

In summary, you poured in (3 changes)(3.35 quarts) = 10.05 fresh quarts, but you drained 4.1875 quarts of the new stuff (~$10 wasted).

Why do feel like I let this get too complicated? Ugh, all this work to do 88% of an oil change... On second thought, just do the single change (50/50 old/new), but do them more often...

eccles

Don't you think that if Mazda considered it problematic, they'd have added some sort of auxilliary drain plug to drain the coolers?

Rotaries with external coolers have always been like this. The 12A's and 13B's in my RX-3 race cars retained several litres in the cooler and lines. Wasn't ever a problem.

jmanolov

Every new car here has to run for 100K miles without any maintenance. Since the RX8 can run for 100K miles without an oil change, then you should not worry about oil problems if you just do the suggested in the manual regular drains even - if they replace just the %50 of the oil, the oil will be replaced with fresh stuff much before something like the 100K miles mark

ProtoConVert

forgive my noobiness.

Could you outline in detail the flow of oil in the car?

eccles

In very broad terms, oil is firstly picked up from the sump by the oil pump. From there, it goes through the external oil coolers, then the oil filter (or is it filter then coolers, I forget), and finally into the hollow eccentric shaft (the rotary equivalent of the crankshaft). Holes in the bearing journals lubricate the main and rotor bearings, and jets spray a constant stream of oil onto the inside of the rotors to provide cooling. The oil then drains back into the sump for reuse.

SPDFRK

You techie guys always make things too complicated. It's simple, just undo your drain plug and leave the engine running the sump will push out all of the old oil. When the oil stops coming out just shut off the car put the plug back in and fill it up, no bad oil left in the system. It's that easy:p

*Disclaimer-To any noobs, the preceeding was a joke please don't operate your rotary engine without oil but but feel free to if your car has pistons they're made for Soccer moms to abuse.

Quick_lude

Obviously having very little rotary experience I will have to trust you on this.. It just seems SO WRONG.. :D

eccles

Would I lie to you?

Quick_lude

:D

Superfan

Haha, I have a Buddy Chist figure on top of my monitor here at work.

notoa1

Have any of you changed the oil?
the dealer changed my oil and they had to add 8 quarts.
It appears that all the oil drains out

eccles

They may have charged you for 8 quarts, but without disconnecting the cooler lines, removing the engine and shaking every last drop out of it, there's no way that they actually put 8 quarts into it unless the level is now 3/4 of the way up the filler neck!

Seriously, yes, several of us have changed our oil, and we've all used 3.7 quarts as specified in the manual. It brought mine right back to the full mark on the dipstick.

notoa1

the dealer changed my oil at 1800 miles
8 quarts came out

notoa1

actually they charged me 24.95 because that is there price for an oil change. when I picked it up they said next time they might have to charge more because they added 8 quarts.

sferrett

I'd check the level and make sure it wasn't supremely overfilled.

Perhaps they drained (some amount) out, and then looked in the manual which says (around) 8 quarts capacity, so just dumped in 8 quarts without looking at the level on the dipstick.

This would be a bad thing (indeed).

If they say they put in 8 quarts, and the level is not over "F" then you've either been duped by the dealer (ie: you'll look in the book, it says 8 quarts so you don't argue with them) or the other folks on the list who've changed their own oil somehow got it wrong.

Simon.

jonalan

So, do the dealers know how to drain more of the oil than us "DIY"s? We're getting conflicting stories here.

eccles

I'd be going back to the dealership and asking the technician to demonstrate exactly how he managed to get more than twice the specified amount of oil into your engine.

If he does indeed have a way to completely drain the system, I'm sure we'd like to know about it, and if he's pulling a fast one in order to get a few free quarts of oil for his own car, I'm sure the dealership would like to know about it!

notdeafyet

The engine's TOTAL CAPACITY IS 6.7 QUARTS. So even if dealers have some super-duper oil drain technique, 8 quarts would be an overfill... which as I understand can cause engine damage.

neit_jnf

I'm seriously considering this gadget: http://www.wetstart.com/default.htm Do you think it's any good? Supposedly you can do a complete drain with this as another of its benefits.