A Point To Ponder Concerning Overfilling Your Oil!
 

I don't want to beat this issue to death but I had a question concerning over filling of the oil in our rotary engines.

We all know-well most of us anyway know that the crankcase in a piston engine is open to the oil pan, that is that the crankshaft is accessable thru the removal of the oil pan. That isn't the case with the rotary as the crank or eccentric shaft runs down the center of the engine and the oil pan is sealed off from any moving engine parts. Over filling the oil in a piston engine will cause the rotating crankshaft to come into contact with the oil and start to splash it arouund causing things like posible oil starvation, eccessive oil consumption and the added resistance of the crank traveling thru the oil.

So my point is how does overfilling the oil in the rotary cause engine damage when the oil is seperated from any rotating engine parts by the intrinsic design of the engine case. In essence we have a dry sump system with a collection container in the form of an oil pan? The rotors or eccentric shaft never come in contact with the oil in the pan. Wouldn't the oil just back up out the dipstick tube and/or filler neck?

Things that make you go hmmmmmmm!

:D

I have wondered the same thing....thanks for asking...any body have Ideas?

Well I just picked up my new RX8 today and it was overfilled way- way over the dipsticlkline- the dealership said it comes with oil from the factory- there were no techs to drain it since it was saturday. I took the car anyway since I had no other (sold MY Probe GT on friday).
I kept the revs low - about 4k or under- and will take it back on tuesday.

Does anyone think it comes from Mazda with all the oil in it?

Hey emaillists, I just bought my RX-8 after owning a Probe GT also. Great minds think alike! Were you on ProbeTalk? I now have two 94 PGT's for sale.

Oh, and interesting question Nut. I was thinking something along this line also but hadn't formulated it fully. Mine was filled very high from the factory also, but I don't think it is overfilled (the oil level is at the H on the dipstick). They must do this to prevent people from getting low on oil from the inherent oil consumption during the first impression/break-in period.

Maybe I should have the Moderator move this over to the Tech forum! I should have done that myself but I get stuck on this one and forgot where I was at!

Yes mine was way over the full mark when I got mine also. I know the kind of damage that can and will occur in a piston engine by over filling but with no rotating masses coming into contact with the oil in a rotary, I don't see what kind of damage can occur

Yeah!, i also noticed that mine was overfilled. I went to the dealership and asked and they let me check one of their demo cars that had 500mi on it. It was overfilled also! I was worried about this thx for bringing it up.

Another couple of Probe GT owners! Very good! I still have mine, along with a couple of other cars. Beginning to look like a used car lot here.

Anyway, I would bet too much oil will fill up the available space in the 'oil tank' and cause the oil not to drain like it should from the shaft area...could be bad news. Don't know for sure...just a guess on my part.

I'll have my oveerfill corrected tues or wed I hope.

Meanwhile I have been keeping the revs below 4500.

Demon- how did you end up with two PGT's? I was sad to see mine go on Friday, but got the 8 the next day- so it was OK by me.

I had accidently overfilled my oil by almost 1 liter. I found that the oil went from clear to black. I then drained the entire contents and started again.

skc

i filled my oil from low to high and it went from black in the can to milky in the car ;)

I bought the first one new in Dec 94 and it's been getting the usual Probe issues - you know, clunking front suspension, CEL light, etc. I thought I'd get another one last fall and "project" it. Bought a set of Ground Control coil overs with Tokico Illuminas and cat-back exhaust. Then I decided it was going to be waay too much trouble and went with the 8. I'd say that it was a definite step up!!

There's another one on here too . . . I think his ID is pr0ber or something. I saw he had a '97 PGT in his sig. Pesky little cars, but you get attached to them. I'd still love to have one in good condition to play around with.

I know what you mean. I currently have the 8, two Probes, a Honda Accord, a Dodge van . . . and if that's not enough, I have a Suzuki SV650 too. Yes, my neighbors love me!


Sorry about the thread hijacking all, we can now resume the regularly scheduled oil overfilling topic now. :)

Higher oil pressure causes that oil to find the easiest way to escape and relieve the pressure. Not sure where that is in the renesis, but in the 3rd gen RX7 there would be oil forcing itself out around the turbos. And if the seals on your turbos and oil coolers)were really good, then it was possible for you the oil to force itself out of the oil gaskets & seals at the front of the engine.

A little bit of overfilling will not kill your engine. However overfilling by a couple of quarts can increase the pressure enough to cause that oil to find the weakest link in the system.

*edit*
because I just woke up and I can't spell to good :D

That still does not make a lot of sense! I hear what you are saying but the oil in the pan is not under pressure. If anything the oil would be under a vacuum/suction as the pump is sucking oil out of the pan and into the engine. The oil would then in essence trickle down back into the pan so where is the pressure? If it was under pressure it would find the point of least resistance and it would go out the dipstick tube hole.

Moderator - thanks for the move.
 

Also - the amount of oil in the pan has no bearing on the oil pressue in the engine as this is controlled by the oil pump.

Anyone heard of a Fumoto Valve? Put one of those in and overfilling your oil becomes a moot point. You can drain as little or as much of your oil as you want in a second. I installed one and it works like a charm.

... in steps another f0rmer PGT owner...

My car was overfilled when I bought it, and was overfilled again when the dealer changed the oil... it seems its goal in life is to be overfilled

http://www.thetoolwarehouse.net/shop/MIT-7201.html


get one of these and overfill is never a worry again

overfilled oil
 

Yes- mine was overfilled also. I took it in, they ck'ed it-wrote down that it was overfilled and then wrote that they adjusted it to proper level. Got it home and checked it myself- THEY DIDN'T REMOVE ONE DROP!!! Now I have the oil light coming on and get to take it back to them and see how they handle that. :mad:

I told the service writer today that my oil was overserviced also. He proceeded to tell me that he had just recently learned that keeping it on the high side (over filled) keeps the oil light from coming on!....say what? I've never heard that about any car, but this is my first rotory.

Anyway, I can't understand why a service department would admit a problem and their fix is to do something non-standard such as this to compensate for faulty engineering. Of course when he told me this, I bet he wasn't thinking of what the consequences would be to continue to operate like this.:mad:

It is much easier and faster to make excuses and do nothing than it is to get under your car and drain some of the oil back out.

Snakeoil and BS from service guy
 

Did you ask him for a mirror so you could look real close and see if you saw IDIOT written across your forehead, 'cause that's exactly what he was trying to play you as. I assumed you slapped dogsh** outta him for that stupidity.

I have 30 years experiance with the Mazda rotarys and THERE IS NO PROBLEM IN SLIGHLY OVERFILLING THE OIL SYSTEM. As the original post stated, the system is basically a dry sump system. There will be no affect on oil pressure either. The only thing that can happen is if extreem overfilling causes the crankcase ventilation system to get oil into it. I really don't think some of the oil on the air filters problem is caused by overfilling, but possible. I commonly overfill my 8 (to use the entire qt.) and have had no problem. The RX8 is not a turbo and turbo's typically have a special oil system to handle the very high speeds and heat, and can and often do fail.

On the Renesis, I think overfilling the oil would cause a higher probability of oil getting sucked into the intake tract through the PCV system. PCV (Positive Crankcase Ventilation) is necessary - if the oil system was actually sealed, you pressurize the crankcase and cause oil leaks, oil smoke, etc. This can cause higher than normal air pressure. Anyhow, the trick is to vent the crankcase so it can "breathe", but emissions-wise this is not friendly. So, the crankcase vents to the intake tract, where any oil vapors are sucked into the engine to be burned and cleaned by the catalyic converter.

If the oil level is too high, the oil can get up to the level of the crankcase vent (especially in hard cornering when oil "climbs") and get sucked into the intake. This makes a lot of mess, coats your intake tract with oil, and can make the car smoke as it burns off all this extra oil.

Are you going to cause any damage? Probably not. Should you get it fixed? Yes. Having the oil level at the Full mark is fine, but over and you should definitely get it remedied.

On turbo rotaries, it can be more of a problem as the turbo's oil return dumps into the front cover to the oil pan. High oil level can back up the oil return from the turbo, causing oil to back up into the turbo and get burned in the exhaust. Makes a big nasty mess at the turbine, and is quite embarrassing :).

Dale

I have an 8- I use for racing only- I would not recomend this- for warrany reasons-but those of us that race the new RX 8- use mobil 108 filters and genearally 5 qts- Penz-5/20
Of course we also have back seats removed/roll bar/ no Cats/ rev-limiter/ac/radio-MUCH more cooling
These cars are built for speed, and love to run!!

i have a 94 Probe GT, and my new RX8 (both black!). not selling my probe though!! i still love it!

james
president BAPOC 1998-2000