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Coupes & Convertibles Mazda RX-8 Mazda RX 8 Engine Failure Problem
40 messages, Last post on Nov 29, 2009 at 1:32 PM
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Replying to: oldtimer2 (Feb 18, 2007 1:17 pm) Now when this happened recently to my RX-8 AT, I thought, no problem, cause that super hot CAT is going to burn that plastic bag to a cider in one day. Three weeks later, the plastic is still there, very very slowly turning a light brown color and smelling with that hot plastic smell. I've driven the car on the highway, and revved the engine to 6000-7000 fairly regularly in city driving. That plastic grocery is not NOT burning away. It's not even turning black. The plastic grocery bag is simply evaporating under low heat over a period of many many weeks. The way this little incident is playing out, I'd have to say, there does not appear to be very much heat difference at the CAT between my RX-8 any other car I've ever owned.
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Replying to: trispec (Feb 21, 2007 3:18 am) There are many diferent types of catalytic converters but the two basic types are those that do and dont have air pumps. the one on the RX 8's, in order to do a better job at cleaning up the eshaust gas, has an air pump which pumps air into a port in the eshaust system ahead of the cat which enables the cat to better burn off the bad sxhaust emisions. I don't know what your reply has to do about being duped by USA Masada as to why RX 8 engines are failing, which I wrote about, but what you said was interesting ....and there you go with an explanation about RX 8 Cats, their fresh air pumps and air injection ports..........Later,......and good luck with your RX 8 and dealer when the engine fails because you are forced to use the to light 5W-20 weight oil....when throughout the rest of the world Masda Japan requires in the owners manual that 5W-30 oil must be used to protect the engine for a long life (without having to be rebuilt numerious time before and after the warranty expires) for the car to run for 200,000 miles, as promoted by Masda sales. I wonder who Mazda or Ford buys their oil from, so I can look up the specs and compare it to the RX 8's actual operating temperatures and oil shear requirements of the engine. I expect the findings will suport Castrol's recomentations that light 5W-20 weight oil (as required by Mazda USA to meet warranty provisions) should not be used in cars that are ever driven long distances or more than, very short trips, to prevent over heating and breaking down the oil protection of the engine. If you were thinking by mentioning that the plastic bag not melting off Catlytic Converter has any thing to do with the operating temperature of the engine it dosen't !!! In addition to many other factors effecting the operating temperature of metal parts in the rotary engine, remember that (1) the speed (friction)of moving parts in the rotary engine, and (2) the much lighter weight and much smaller exterior surface of the engine to "sink" heat from the rotary engine, compared to a standard piston engine...all causes the rotary engine to opperate at least 50% hoter than piston engines, which therefore might survive the light weight 5W-20 weight oil...where the rotary engine can not !!! |
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I've heard that Honda, Ford, and Mercedes Benz all recommend 5W-20 synthetic for their cars now.
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Replying to: fedlawman (Feb 21, 2007 7:23 am) As you may know Honda, Ford, and Mercedes Benz in addition to Mazda, all have problems meeting EPA's miles per gallon (MPG) requirements for their fleet of cars to reduce more $$$ of the huge (million $$$) fines that EPA charges. In order to reduce (huge) MPG gas fines, they have been recommending like Mazda the use of the very light 5W-20 weight oil to cut down the resistance to movement of parts in the motor caused by the heaver oil adhering to and protecting from metal to metal friction. To understand more about EPA-MPG gas requirements and huge fines look on the web under EPA Gas MPG Requirements and (huge)Fines. In this connection though, I understand Mercedes Benz has changed their recommendation for oil back to a 30W base oil and Honda is also considering doing the same, if not already done so, to prevent further engine failure claims by their valued customer. I guess Mazda customers come last !!! More importantly remember that Castrol, who is the standard for good oil protection, does not recommend the use of their own 5W-20 oil under the same circumstances. In addition Ford makes Motorcraft light weight 5W-20 oil because they also own 33% of Mazda and probably have bigger problems meeting EPA - MPG gas requirements without EPA charging huge fines for their fleet of cars. Again the EPA web site gives examples of huge (millions $$$) fines that charges and manufactures want to reduce. |
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Replying to: trispec (Feb 21, 2007 3:18 am) Hay, I just caught on to the point you were trying to make in your response to my post about the RX 8 engine failures, light weight 5W-20 oil and hot engines breaking down the light oil. Sorry I had tunnel vision when I read your response. If my response to you was interesting OK, if not ignore it. Now hopefully in reply to your response, I think you were making the point that, if your Catalytic was not melting the plastic bag wrapped around it, then the engine should not be very hot. Very, very interesting deduction Dr Watson. I can only believe you as to what you have observed. Years ago the Cats were so hot that they caught everything on fire including dry grass, floor mats inside cars, things in trunks and oil mats under cars in ones garage and burned down houses.....which was all not good. I also remember when I was a kid replacing mufflers and Cats at a Sears auto garage for extra spending money, and that one also had to be careful in taking off a Cat. I was told that any pounding or cutting on the Cat could make a spark that would cause the cat to blow up in my face. I surmise that the car industry has done something to make the cats safer and cooler because the fire problems have stopped. But how cool and how the industry did it I can only deduct. I suspect that they double walled the outside of the Cat and may have routed some of fresh air into and between the outer double wall of the Cat to make the outside more cooler. I only guess, as an Engineer. I do know though the inside of a Cat must burn glowing hot to burn off unwanted gas in the exhaust but how hot this will make the outside of a modern Cat I do not know. But I might be concerned, if it was to cool because this might mean that the cat is plugged up with blow by oil through heat failed engine seals into the Cat. I know the tips of my exhaust is so hot I can not touch them, but I have not tried to put my hand close to or touch the outside of the Cat after a drive. Your observation was a good one to ponder. Seals in engines though are failing due to too much heat as is evident from failed engines and cats plugged up with oil as documented on RX 8 owner forums. And mazda is building a factory according to their announcements to rebuild failed motors, but they will probably be rebuilt the same as the failed ones and use the same required oil to only fail again and again. Good luck with your RX 8. I have thought about having the Mazda dealer put in a larger oil cooler to keep the oil from breaking down on long drives in hot weather. A larger oil cooler should not violate my warranty, where in using 5W-30 oil, like the rest of the world uses, would in the USA. Oh, how many miles do you have on your RX 8 and have you yet taken many long 4 to 8 hour drives in hot weather with out any adverse engine symptoms ??? I am afraid to take long drives in warm weather after talking with a few master service techs that used to work at Mazda dealerships. Maybe a larger oil cooler is in my future........Later and thanks for the reply.
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Replying to: oldtimer2 (Feb 21, 2007 8:36 pm) Here in Boston, and around New England, where I take my family on day trips, I can't really say that heat has ever been a big issue. We do have a maybe a dozen days of 90 plus weather each summer. And my commute into Boston was an hour of stop and go each day, but I bought my 2005 RX-8 AT brand new with 5 miles on the odometer in September so that first year of ownership started out with cool and cold weather driving for about 10K miles. We've taken three 2000 miles trips, all in the winter between Boston and the mountains of NC. We've taken a single trip to Maine in July, 300 miles. Now if I've lived in Texas, where my brother's family practically lives in an outdoor pool all summer and where they had forty straight days of 100 plus heat, I might be worried as hell about owning an RX-8. |
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Replying to: oldtimer2 (Feb 18, 2007 1:17 pm) 1. If you used 5W30 the entire time up until you had to take the car in for whatever reason, would Mazda notice if you switched back to 5W20 immediately prior to bringing it in? Could switching oil grades cause additional problems? 2. How much gas mileage do you actually lose by using 5W30?
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Replying to: rhester (Mar 13, 2007 1:08 am)  There is no way they could tell by looking at the oil (or even by having it analyzed - it gets changed too much in use). However, they may ask you for "dated proof of purchase" of the 5W20 that is allegedly in the engine. I don't think switching grades would cause any problems due to the switch. I don't know about the RX-8, but I've seen claims of about 5-10% fuel economy difference between 5W30 and 10W30.
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Replying to: pathstar1 (Mar 13, 2007 6:19 am) In that case, why doesn't everyone just use 5W30 until the point where the car needs to be taken in? Shoot, perhaps if we all used 5W30 we wouldn't NEED to take it in  Anyway, it doesn't look like I'll be getting the RX-8 I was spying. The dealer wants over 30k for it. A 2006! Ok, it is a Shinka package but that still Blue Books for $28k. I digress...
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Replying to: rhester (Mar 13, 2007 7:51 pm) I did not like the Shinka because it seemed like a big deal over an otherwise plain looking car. But everyone has different fantasys. Look at the Grand Touring model with ground effects and a great appointed interior with red leather accents, which makes you think you are getting your money's worth. I also had the dealership add some Mazda Speed extras which makes more horsepower and is still under warranty since the dealership installed the parts, so they say. Break the car in carefully, then find out the fun of using 3rd gear to put the rear bumper huggers in the distance. Third gear will take you to 80 MPH in a heart beat. If you want to make sure that the rotary apex seals are being lubricated properly, pour around 6-8 ounces of non-synthetic 2 cycle oil into your gas tank as you fill the tank like those who race RX-8 cars, to be safe than sorry. Face it, Mazda will probably never officially tell anyone to use 5W-30 or 10W-30 oil instead of 5W-20 oil because then EPA would be all over Mazda to pay millions in fines for exceeding MPG requirements for their entire fleet of cars. I have read on one web site that the difference in miles per gallon between the to oil weights is only about 1/10 of a mile per gallon which means nothing to us, but for Mazda when multiplied and averaged for the entire fleet of Mazda's sold it adds up the lots of gallons per mile and lots of $$,$$$,$$$ of EPA fines. Mazda would just as soon replace lots of failed rotary engines than pay the fines, so the fine must be enormous. Google for "EPA Cafe MPG" and and get an idea of the fines. No wonder Mazda doesn't give a hoot about how long the RX 8 engine lasts for the consumer. In fact if the engine failures did not also ruin the catalytic converters, which EPA requires must function properly for about 6 years, Mazda probably would not ever care if RX 8 engines failed.
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