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So why are we adding oil at all?

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Old 11-03-2004, 06:11 PM
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John:

First of all my apologies - I didn't realize your screenname was actually a contraction of your name. There are so many idiots that post on these boards that seem to be professional trolls, that it's easy to assume first, ask questions later. I'm sure you're a good guy.

That said, we RX-8 owners are VERY passionate about our cars. Oil consumption seems to be one of those things that if you either never owned a rotary powered car, or don't understand the technology behind it, it just seems like it's a result of poor engine design. As I've said over and over, oil consumption in an RX-8 (or any other rotary engine for that matter) is by design. The engine has a powerful oil pump that pushes oil through the eccentric shaft (the rotary equivalent to the crankshaft in a piston engine) and into oil journals and passages in the rotors, where the oil makes it way out to the apex seals of the rotors - leaking past them and lubricating the seals and the rotor housting (trochoid) walls. And, it is guided out to the side seals where it leaks past and lubricates the sideplates. Both of these actions cause the deposited oil on the seals and the walls to be consumed by the engine as it runs. It cannot drip back to the pan because there is no pathway. Hence, oil consumption by design.

This is necessary because there is no reciprocation of the engine whereby parts of the engine can be exposed to oil spray, lubricating and cooling them. ALL piston engines have some sort of method of spraying or splattering oil up underneath the piston crowns and cylindar walls. Most modern piston engines have similar oil passages built into the bottom of the engine, and these "jet" oil up under the reciprocating pistons, lubricating the piston walls, the skirt of the piston, the wrist pin (the pin holding the piston rod to the piston itself), and the rings. Most piston engines, as I'm sure you're quite familiar, have at least two or three rings - the bottom pair (or one) is the oil control ring which is designed to keep oil out of the combustion chamber.

Rotaries, because they don't have this oil-spray filled chamber to work with, like a piston engine does, has to rely on the oil passages pushing oil out to and past the apex seals. This action results in consumption of oil.

The Mazda RX-8 owner's manual (sorry, I can't cite page here, but if you require me to, I'll be pleased to look it up for you since you don't appear to own the car yourself) states that the engine's oil consumption may be as much as a quart every 600 miles. In practice, most of us that post on this board report consumption in the quart every 3000 miles. I report same, although I only have one data point to report that on as my car has only 3000 miles and it's just consumed one quart.

Car & Driver's article that you cite was published in the magazine in April 2003, and posted on their web site then. As you can imagine (or maybe not, I guess I shouldn't suppose for you), they do not publish their entire magazine's contents in the web site, only highlight/spotlight and major feature articles. The web site is free, and they are in the business of selling you their magazine, therefore, much of the magazine content is not published to the web site. I have subscribed to C&D for more than 20 years and have nearly every single magazine still from that period.

Being a former RX-7 owner and being very keen to have another rotary car, I read every scrap of info published in C&D, R&T, Autoweek, Automobile, Motor Trend, Popular Science, Popular Mechanics, and others, about the RX-Evolv concept car, the new Renesis, and finally the new RX-8. I distinctly remember this article from when it was published in the magazine and being agahst that they were claiming oil consumption of a quart every 10,000 miles. No car company in the world would publish a figure like that. I thought it had to be a typo. Especially since I had owned a 1985 RX-7 with the 12A rotary and it burned a quart every 700 miles.

Sure enough, in the May 2003 issue of C&D, there was a small retraction printed towards the end of the magazine that the 10,000 mile total was a typo, and that 1,000 miles is what Mazda was saying about the Renesis.

What I take objection to is that guys like you, , who clearly do not own the car, seem to take sport and fun in trying to find the car's achille's heel. This on a board of either owners of RX-8s or fans of RX-8s. You're citing an article that has been retracted, and then you get angry when I point that fact out. Well, sorry I didn't note the month and article, but now I have.

I am not going to take the time to dig the magazine out of my stacks, thumb through it to find the page, scan the retraction, and post it up. It was the May 2003 print issue of C&D. Good enough for me. Go to the library if you don't believe me.

I'm at a loss to understand why you care so much about trying to knock the RX-8 and it's rotary engine, the Renesis.

Quick aside to Icemaster: I agree that the NORMALLY ASPIRATED Renesis doesn't put out as much horsepower as a forced induction twin turbo FD-series RX-7 engine. But that's about as surprising as noting that Pamela Anderson isn't as good looking as Janet Reno. Using your argument, you could say "but hell, if Janet Reno were half her age, blonde, had perfect skin, and incredible breast implants, she'd be just as hot". Yes, you're right, the Renesis under-performs the FD RX-7. But the FD cars cost $40 GRAND in 1993, and didn't sell for **** in the USA. Yes, they produced amazing horsepower, but the the cost killed it. Mazda brought out a mass-market, four-seat, four-door sports car, without product-cost adding things like twin turbos. And guys like me, who could not justify 40 large in 1993 on a two seat car (this after having had one kid with two more on the way), found it perfectly affordable to spend 30 large on a four seat car 11 years later. Ok, so it's down on power a bit. I still LOVE my car. Best car I've ever had!

If you compare an RX-8 to a second generation, naturally aspirated car (the most direct comparison) you'd see that the Renesis makes 80 more horsepower than the most powerful variant of the naturally-aspirated, fuel injected 13B engine. I'd say that's an improvement. Comparing it to the twin-turbo is absurd.

Last edited by StewC625; 11-03-2004 at 11:06 PM.
Old 11-03-2004, 07:57 PM
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StewC625:

I am aware of Mazda, and the rotary engine.
I know about oil consumption, especially a rotary.

The point of the C&D article was that ‘the only way’ the Renesis engine (with side ports)
is possible without being clogged is due the metering of oil. That metering is what it said was reducing the oil consumption to 1 quart per 10,000 miles.

10,000 does not seem to be an excessive number to me, since I get way more than 1000 in my RX-8 and I know that RX-7’s got 3000 or more with a 12A rotary.

Again, what volume and page is the C&D retraction on?
Can it scanned and posted to the forum?

I for one would like to see it.

The oil viscosity may also be issue, since I see 10w-30 is acceptable for use, and might make a difference from using 5w-20.
Old 11-03-2004, 10:13 PM
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John:

You obviously didn't read my post in full, did you? - see pulled quotes below. I remember it. If you want to hunt it up to prove me wrong, go for it cowboy. I'm done with this bull ...

You still haven't explained to us why this is a big deal to you, or should be to us. Are you saying that because I have to pour a quart of oil into my car at 3000 miles that I should call Mazda and say it's defective? Should I be outraged? Should I ignore the dipstick and let the engine run low on oil and burn up?

Sorry, call me crazy, but I'm missing your point. Yes, I understand it was published. Beyond that, WHAT IS YOUR POINT?

Your thread title "So why are we adding oil at all?" implies you think that your car is defective if you have to add oil. Ok, cowboy, knock yourself out. Don't add oil. Let us all know how it comes out, OK? I plan to check mine, add oil when it needs it and not worry about what was published on the subject.

Help us understand your pain.

Stew


Originally Posted by StewC625

Sure enough, in the May 2003 issue of C&D, there was a small retraction printed towards the end of the magazine that the 10,000 mile total was a typo, and that 1,000 miles is what Mazda was saying about the Renesis.I am not going to take the time to dig the magazine out of my stacks, thumb through it to find the page, scan the retraction, and post it up.

It was the May 2003 print issue of C&D. Good enough for me. Go to the library if you don't believe me.

Last edited by StewC625; 11-03-2004 at 10:15 PM.
Old 11-03-2004, 11:45 PM
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sorry, that I missed your statement that the 'retraction' is in May 2003.
this is not about proving anyone wrong! so f'ing chill out.
Post if possible or say no way. I’ll ask C&D

Real simple as the thread says

if 10,000 is possible or is what was originally engineered into the renesis,
I would like to know.
I currently get more consumption than I think should be occurring

example: use 10w-30 versus 5w20 then maybe 'not need to change oil except at 7,500
scheduled miles', Mazda has said 10w-30 is o.k. so 5w20??

I only asked for input from members, not a f'ing battle
Old 11-04-2004, 12:02 AM
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Well from my own Rx8...I change my oil when the low light comes on.. and more then liky its always around the point when it needs to be changed.. I drive 5k and change oil.. nothing more then that.
Old 11-04-2004, 12:20 AM
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thanks
Old 11-04-2004, 06:47 AM
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Sorry John, your tone suggests battle.

What's your current consumption? I'd say the owner's manual is your guide ... it says a quart every 600 miles is within normal range.
Old 11-04-2004, 08:55 AM
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I can only give an estimate because I do not have enough mile to average.
.
added 1 qt at 2000 miles and that did not come close to filling it.
so I est 1 qt at between 1000 and 1500 miles. normal driving - no racing

other forum users say they do not need to add at all, and some say it gets
better as the get more miles on the vehicle. so are they otl??? not lickly!!
Besides the renesis is supposed to get better consumption than other rotary
engines according to other threads. And those threads say older rotaries got
1 qt per 3000 or better. so I figure my consumption is worse with computer control!!
or that 5w-20 is too thin and falls out of the engine. Either way something is not right.
Don't seem right.
Old 11-04-2004, 09:03 AM
  #34  
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Hi John:

I understand how frustrated you must be. Actually, and please take this for nothing more than my opinion, if you had just stated this exact information upfront, rather than posting these articles and raving with the tone you've had about the articles, you might have gotten a lot further a lot sooner.

According to the info in the owner's manual, a quart at 2000 miles is pretty reasonable. I wouldn't be upset if I were you.

Here's my history:

Car delivered, 38 miles on it. Broke it in gently for 500 miles, then took it on a 600 mile road trip. Oil was slightly above the top line on the dipstick prior to the trip, and about 1/4 below top line after the trip. Added 1/2 quart at 1100 miles, which brought the engine back up above the top "full" line.

1500 miles - oil & filter change, M flash, at the dealer. Dealer refilled engine to over the full line again.

3050 miles, oil was half-way to the add line, added another 1/2 quart, which brought it to just short of the full line.

So, mine looks like it's burning a quart every 3000 as I'm adding a 1/2 quart every 1200-1500 miles. Seems perfectly fine to me. It's supposed to consume oil.

Rather than ranting on this board ... have you contacted either Mazda or your dealer about this? What you're describing seems perfectly normal to me. I know that's not the answer you want though.

Stew
Old 11-04-2004, 05:07 PM
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I have contacted Mazda, they seem way less than forth coming when asked questions.
Maybe they consider questions a CYA response thing. (the service industry sucks today)
what can one expect, give a low end number and skip reality.

Even 3000 / qt would be nice and is about the bottom line for me, less and I will be SERIOULY considering getting another vehicle. That is why I researched before I bought A 8 AND I figured , based on the articles , that the rotary was getting better not worse.
I checked this forum and the web a lot before buying.

I'm not expecting 10,000 but hey! If Mazda states 300 or 600 and owners are getting 2000-3000 then maybe they should state in the manual or in other source a realistic
range we can use as a guide.
example: IFthe 300-600 number is 'stated and is valid' for say people who use 5w-5 oil and race at 102 m.p.h. at Laguna Seca , and I don't do that and get 300-600. I would want to know that I should be seeing the dealer because it’s an issue. Conversely if using 10w-30 with normal driving should rate a bare minimum 4000 mile, that would be nice to know

that’s why I asked, even 300 to 2000 or 3000 is a major range for consumption

Yes, stew if you got the page number for the MAY C&D article, cool!
Old 11-04-2004, 05:57 PM
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[QUOTE=StewC625]John:


As I've said over and over, oil consumption in an RX-8 (or any other rotary engine for that matter) is by design. The engine has a powerful oil pump that pushes oil through the eccentric shaft (the rotary equivalent to the crankshaft in a piston engine) and into oil journals and passages in the rotors, where the oil makes it way out to the apex seals of the rotors - leaking past them and lubricating the seals and the rotor housting (trochoid) walls. And, it is guided out to the side seals where it leaks past and lubricates the sideplates. Both of these actions cause the deposited oil on the seals and the walls to be consumed by the engine as it runs. It cannot drip back to the pan because there is no pathway. Hence, oil consumption by design.

Technically speaking, the oil that is consumed is metered through a device called a metering oil pump. This pump is controlled by the engine computer & delivers a small amount of engine oil directly into the rotor housing at the intake cycle area to lubricate the compression seals / seal sliding surfaces. The amount of oil to add is based on engine temperature, RPM, calculated load, etc....
Old 11-04-2004, 09:04 PM
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John:

Do you understand that oil consumption in a rotary is a designed-in thing? It favries by usage/mileage/etc. but doens't indicate valve guide wear (there are no valves), or blown rings (no rings either) like in a piston engine.

Oil consumption in a rotary isn't a sign of wear.

John if you're that worried about it, sell your car.

I'm done with this thread and the bullshit about oil consumption. Understand your car and deal with it.
Old 11-05-2004, 01:00 PM
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Stew:

Everything you write is fill with anger and hostility. WOW.
Gets worse when the C&D article is mentioned. Interesting.

You ask about

Do you understand that oil consumption in a rotary is a designed-in thing? It favries by usage/mileage/etc. but doens't indicate valve guide wear (there are no valves), or blown rings (no rings either) like in a piston engine.
Oil consumption in a rotary isn't a sign of wear.


The C&D article is quite clear about OIL, OIL usage, metering.

This thread has always been about information NOT BS, you seem to want to change its direction and tone. Sure you are not some ‘MAZDA REP’ out to discourage all discussion of any information that you feel could be other than what shines the brightest light on your product. Hey C&D, EDMUNDS, ROAD AND TRACK and all the other independent sources sometimes differ with each other and obviously with STEW all the time.

Guess Stew is saying the metering system delivers oil at 1 quart per 1000 miles and anyone that is getter better or worse is OTL and need to ignore the issue.

Good thing other were not discouraged and debated ‘m’ flash, brake pad fixes, visors
Etc.

Most likely there is no retraction, Mazda changed some metering formulation, and
No one told Stew

have a good one , john
Old 11-05-2004, 05:18 PM
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Got bigger fish to fry than to worry about, if in 1000 miles of driving or 3000 miles of driving that my $30,000 car is going to burn up a $2.50 quart of motor oil.

Buh bye now.
Old 11-19-2004, 11:57 PM
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C&D has nothing to say about any retraction, so it seems, the 10,000 miles /qt was accurate. since some forum members are getting 2500 to 3000 , which is the actual
12a and 13b non renesis engine consumption, we are still a bit short (7000 miles)
so its back to why? Seems no rotary ever made got only 1000 miles per quart
unless it was run at some red line rpm or with 0w oil.
Old 11-20-2004, 09:17 AM
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give it up.. this is a dead subject.. Car and Driver was dead wrong.. Go call Mazda USA and they will tell you 1qt every 1000 miles... I know my dealer told me about that. Yours probably did to if you bothered to ask.
Old 11-20-2004, 11:33 AM
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Cool

no philodox, mazda quotes 1 quart per 600 miles.

the issue stays the same
Mazda states that they were unable to use side ports in the 12a and 13b because the oil consumption and metering left the ports CLOGGED - and those engines used one quart per 2500 to 3500 miles reguardless of operational parameters.

Now Mazda moves to side ports and quotes one quart usage per 600 miles(and NO CLOGGING) Hey must be magic or fuzzy math!!!

And the RX-8 forum users (other than the mazda reps on this site - which are exstensive) state that they can get between 2500 and 3500 and some 7000 miles. NO ONE states they are using 1 quart per 600 miles.

No way that Mazda is serious about stating 600 / qt when the rotary engine has always done better by about 400% unless there is some real sticky isssue here.
Instead of getting some BS reply from a rep on this how about some real answers to the descripency.
Old 11-20-2004, 11:40 AM
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well I use 1qt every 600-1000 miles, depending on how hard I drive the car. And you know what, I don't car that I have to add oil.. I just wish everyone would stop complaining about the car.. sell the darn thing if you don't like adding the oil and get something where you don't have to pay attention to it.. not ranting at anyone in particular, just in general
Old 11-20-2004, 01:50 PM
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Yuh, but....it was in Car & Driver--it must be true. Let the battle continue!
Old 11-20-2004, 05:19 PM
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Yeah, who would have believed Car and Driver when they said the ports were
moved to the sides of the rotary. But heck, they were right, seen the pictures!

And as usual, if any forum member says anything the rest of the Mazda reps do not like, the thread is trashed, the member is called names, or you folks ay the author is complaining.

Well this is not a complaint, was not posted that way.
So why is Mazda so bend about it?
Maybe Mazda should step up and say the entire C&D article was BS. No ports were moved, no reason to move them, and there was never any clogging issue with the rotary.

They won’t because the article is all factual. This forum has already trashed anyone who
asked about HP of fuel economy.
Old 07-09-2005, 08:38 PM
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i talked to a rotary engine specialist today.. he said NO synthetic..... he also said the best oil to get is VAVOLINE because they dont burn as fast (he has doen studies with oils for a few years now).. just thought id let u folks know.... my car has 600 miles now.... break in is over (according to the manual)... im gona add a half quart of oil in about another 600 miles
Old 07-10-2005, 06:28 PM
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Cool

Hmm... interesting about the Valvoline. I am currently using Castrol GTX 5w20. My car only has 1500 miles though, perhaps I'll switch. I liked the idea of the Royal Purple not leaving soot on the exhaust (and elsewhere internally for all I know). I have also read somewhere (I thought it was on a Mazda site or something) that the renesis doesn't benefit from synthetic. I'll try and find that one and post it here.

Cheers
Old 07-11-2005, 06:28 PM
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Guys! Dino oil is cheap! I use Castrol GTX 5w20 and put in a half quart every 1500 miles at the big price tag of about 3 bucks.

Looking for the point of this ... if you're switching to synthetic to cut down on oil consumption, but the car consumes one quart between oil changes ... and say the car cuts its oil consumption in half ... do the math:

Oil change with Synth oil: 4 quarts at $10.00 quart = $40 in oil for the change plus $5.00 for the half-quart it burns between changes (assuming a 3000 mile interval) = $45.00 in oil.

Oil change with Castrol GTX "dino juice": 4 quarts at $3.00/quart = $12.00 plus another $3.00 for the quart it burns = $15.00 total.

Ok, so you say "oh, but then I'll be able to DOUBLE the interval on the oil changes to 6000 miles." Still doesn't work - you can do 2 1/2 dino oil changes for the price of one synthetic. I'd rather change my oil like religion every 3000 ...
Old 07-22-2005, 12:02 AM
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dont use synthetic. plz read the owner's manual next time. that **** will **** up your car. stay with regular motor oil. use 5w20 when new, and eventualy move to something thicker..
Old 07-22-2005, 05:05 AM
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I use Valvoline myself and last time I changed my oil it was only a quart low. Done at around the 3k interval. Of course, I don't drive the car very hard. I did also here not to use synthetic cause Mazda has not researched it yet. But to each his own. If that's what you like and what you prefer, then go for it. I certainly won't stop you.

Brian
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