chiefy

I know there are lots of threads on types of oils synthetic/dyno etc etc but I am intrigued to know why the US RX8's are changing oil at 3000 miles intervals. Over here in UK we are changing the oil at 12500 miles as per the Manual. Would be interested to know your thoughts? Incidentally many of us are using the recommended Mazda 5 - 30. My car is just coming up to 3000 miles and the oil is still clear.

chiefy

I am amazed nobody seems to have an opinion on this as there is a big difference between 3000 miles and 12500 plus significant cost implications.

The Ace

Your manual, the Greek manual, and I'm betting the US manual all say -more or less- the same thing: oil changes at 10K or 20K km (or 7,5K-12,5K miles). This is the "normal" for RX8 oil changes. This was also true for RX7 oil changes.

Guess what ? Since the oil (mineral or semi-synth 5W-30) is rather cheap, and since oil is to the rotary pretty much what blood is to the human body, everyone and their cousins decided that 5K is already a long interval. Others decided to tighten this and go for 3K intervals.

Seems to help the longevity of the wankel (13B and Renesis) immensely

DrDiaboloco

I don't understand a 3k interval in this car above all others. At 3k, you've already replaced half the oil that went into it at the last oil change, and you're throwing away perfectly good oil. Cars that have oil monitoring functions usually end up with intervals even longer than 7500mi., up into five-digit mile ranges. And yes, I know they're not rotaries.... But at 7500mi, you have already replaced all but one of the original quarts that were in the engine (assuming you let it run to a quart low each time and add a full quart every 1000mi).

I know the argument, "it's cheap insurance"... But changing your oil twenty extra times per 100,000 miles (3k interval vs. 7.5k interval) isn't particularly "cheap".

chiefy

I also think that the more times you change your oil the more likely you are to introduce contamination into the system and every time the the sump has been drained thats another time that the oil pump takes longer to pick up suction again. If the oil is clear then there cant be anything wrong with it - unless it is diluted with petrol after a flooding incident.

fray

iTrader: (1)

The 3k interval is also a way for many US car dealers to gain additional service revenue.

My dealership recommends 5k miles. (Which I believe is also what the book says in schedule "2". Schedule 1, is an oil change every 7.5k miles.)

According to the manual:
Follow Schedule 1 if the vehicle is operated mainly where none of the following conditions apply.
If any do apply, follow Schedule 2 (Canada and Puerto Rico residents follow Schedule 2).
* Repeated short-distance driving
* Driving in dusty conditions
* Driving with extended use of brakes
* Driving in reas where salt or other corrosive materials are being used
* Driving on rough or muddy roads
* Extended periods of idling or low-speed operation
* Driving for long periods in cold temperatures or extremely humid climates

As for "cost" of an oil change, around here it's about US$25 for an oil change. So it's not "cheap", but it costs less then a tank of fuel.

Celronx

iTrader: (1)

Well, I can tell you that I change my oil every 3k miles. If I fill it to the top when I change it, I don't have to add oil before the next change. It never gets below about 25% up from low. That's what about 2/3-3/4 quart below absolutly full. When I do change it, it is very black and smells of gasoline. I really don't think I would feel good going 7.5k between changes. 5k would be pushing it.

Cel

loco4rx8

I follow Schedule 2 of the manual. I figure Mazda knows best. Every 5000 miles should be fine unless you really are rough on the car. I do not actually have any of the extreme conditions that Schedule 2 mentions, but it makes me feel better to follow that schedule.

Spin9k

Here's a thought - perhaps the English are perceived to have better memories and it is believed they will therefore replenish oil as it is naturally burned, whereas here in the US they decided to err on the side of er ah caution, and make sure the oil is replenished by mandating approx 1 qt-use change intervals where the dealer can make sure the oil-level check occurs.

olddragger

iTrader: (3)

every 5k is easy to remember--5, 10, 15,20 etc, when a household has multiple cars/multiple drivers it is a lot easier to keep up with. plus i think it is the right time for my car.
OD

chiefy

Thanks for all of your responses which all make sense. I wonder why though, my oil at 3000 miles is still clear on the dipstick. Like - it is so clear it is difficult to see it ( and yes there is some in there! )

dillsrotary

oil is cheap, engines aren't, just do it every 3000 miles, you're not hurting yourself in any way personal or finiancally. And if you are you shouldn't have purchased an rx8

juanjux

At about 14$ the quart of "Dexelia" (the oil Mazda uses here in Spain, and I suppose also in the UK) I think it could hurt a little changuing oil every 3000 miles. Of course you can use a cheaper oil.

dillsrotary

But i find it hard complaining about changing the oil when its a car to begin with. If you are willing to chance running longer miles then by all means go away because its your property, not mine. But as for personal advice i think more frequent changes will save you more money in the long run than trying to save a couple $$$'s now in the present (especially with a rotary engine.)

DrDiaboloco

My only response to your logic is...

"Why not change the oil every ONE thousand miles? Oil's cheap, and it will save you more money in the long run. Hey, if it hurts you financially, you shouldn't have purchased an RX-8."

Noone's "complaining", as you say, about changing the oil. What we are doing is trying to justify changing the oil more frequently than necessary. I, for one, don't enjoy throwing money down the drain... Which is what you're doing if you change it every 3000mi. No modern motor oil is so poor that it needs this interval, and it is pretty apparent to me that the source of the "if you don't change your oil every three thousand miles you're gonna be sorry, it's cheap insurance against disaster" story are the people who peddle motor oil or make a living changing motor oil (Jiffy Lube and the like).

dillsrotary

i understand, but to justify to change it or not some people will change it more frequently and others will not. Who knows who's right because its a tough question to prove has only one answer. Everyone will do it how they see fit, i was just expressing my opinion on why i believe you should do it more often.

scottmhr1

I agree, the only ones really pushing for 3K changes are the jiffy lubes etc. I don't drive the 8 except on weekends so change every 6 months or 1500 miles, lol. The jiffy lubes are just trying to rip you off by making the 3k changes (harshest conditions under any manufactureres data) to make you do it more often than needed. Who says the rotary needs more? Mazda does not. Just check it now and then because it uses more than most cars. Never says change it more than that, and believe me, if they thought it might cause a problem they would say to change it more often.

nycgps

iTrader: (1)

I do mine between every 2-3K now.

Oil is cheap. Im doing it about 4-5 times a year I think. and I think it will cost me about 40 bucks each time ? I think Im ok.

I like to change my 13b-MSP's blood every so often. To keep it happy. Oh Full Synth Blood here ;-)

nycgps

iTrader: (1)

https://www.rx8club.com/rx-8-media-news-11/jiffy-lube-cheating-customers-92682/

The Ace

And to put things in another perspective: I think that spark plug changes are the same over there (UK and US), so I'm guessing it should be done at 60K km (or 40K miles), right ? This is the first "big" service/tune-up that you have to do.

From our experience (in Greece), spark plugs are already pretty much useless at around 30-35K km (or 20K miles). So, should you follow Mazda's guidelines, or will you decide to do what's best for you and your car ?

And being a former RX7 owner, I can assure you that frequent oil changes ensure that the engine stays happy, since leaving the same oil (especially mineral) inside a rotary for 10K or 15K km is a bulletproof way to ensure your engine's early demise....

chiefy

Assuming that the RX7 was the Turbo version then the oil quality is more critical. If the oil in the engine has not been diluted and the oil filter is not clogged then there should be no reason why the oil should be changed so the design intervals should take this all into account ( with a safety margin ) However ---- I wonder if the oil condition is more critical in these Rotary's because of the Oil Injection?

The Ace

Indeed it was a TII, so oil was even more critical than it already was for the N/A versions

But nonetheless, since oil plays a dual role in all rotaries (lubricating and cooling) and with higher percentages of participation than in reciprocal engines (oil cooling is about 60% of the total cooling effect, whereas in other engines it's down to about 30%), even the slightest impurity or general problem with the oil becomes a big factor. That's why it's even more important to make sure that the oil stays in tip-top shape....

Ericok

The oroginal poster was making a valid point. Why would Mazda, which sells cars worldwide, have a longer oil change interval for one part of the planet than another? It is, after all, the same car. In addition, why would Mazda recommend a heavier weight oil for everyone else while recommending a lighter one for the US (fuel economy being obvious but does the lighter weight affect engine longevity).

My personal experience (with a non-rotary) leads me to believe that frequent oil changes are over rated. My Toyota van, which has 233,000 miles, has its oil changed religiously every 7,500 miles (just when the oil change light says to change). It runs fine, burns no oil, makes no noises, passes emissions and the engine interior is clean.

DrDiaboloco

Another question to ask is what is this "proof" that more-frequent-than-recommended oil changes are beneficial. Anecdotal stories along the lines of "I changed my oil every 3k miles and the engine is running fine" are countered by tales like the one above... Furthermore, stories of 7.5k mile changes ending with an engine failure don't prove, at all, that more frequent oil changes would've precluded that happening.

I sure wish I could find an article I read a few years ago in one of the big US auto magazines. They actually had their (used) oil analyzed at around 3k and found that even though it LOOKED dirty, it was far from being "used up". All these modern oils have additives that really determine when the oil needs to be changed, in the sense that the oil itself is not going to go "bad", it's just a matter of when the additives are no longer doing their job suspending and isolating the gunk that gets into the oil... and that modern oil can go far, far longer than conventional 3k wisdom dictates. I recall the article also had off-the-record interviews with oil specialists (as in people who work in the engine oil industry) who admitted that the 3k interval is a moneymaker and has no basis in fact.

No, they weren't working with a Wankel in that case... But the difference isn't so great that I'm going to discount those findings, esp. since this car burns oil in combustion and needs to be topped off with.... tada!.... fresh oil. I'm keeping the oil cleaner, longer, by burning through it and adding fresh oil, so I see no reason to worry about a 5kmi engine change.

Actually, as of late, my bigger concern has been how much TIME before an oil change. I just changed mine at 4k miles because it'd been 5 months since the last change, not because of the mileage. It took about two quarts in that 4k mi, btw.

chiefy

I agree - time is a very important factor which will also cause deterioration of the oil. People tend to assume that when the oil becomes darker that it has "had it" - but in actual fact it is just doing its job and keeping those particles in suspension that are so small that they pass through the filter and prevents them from being deposited around the internal spaces of the engine. Well as I am adding about 1/2 a Litre every 1200 Miles and at 3000 miles my oil is crystal clear I feel pretty confident that it has many more 1000 of miles left in it.