RX8_GT

Let's see $100 for each oil analysis vs $120 for all the extra oil/filter changes to 100,000 miles.

.... I pick Door #2

went_postal

So... Why oh WHY would you use synthetic in a Rotary? That is just bad juju as this car purposely burns oil. From what I understand, synth. will burn but not completely... That being the case it is supposed to cause issues with the engine.

As to how often... I do mine between 3 and 4k.

I also would like to know why someone would let the oil actually get down to the lower line on the dip stick! what is with that? About every other gas tank I drop some oil in the car and top it off... Not sure WHY you would let it run down very far. Seems like a recipe for disaster IMHO.

If I recall correctly, my manual says 7500. Dealer says 4k. I do it at 3k-ish. I would think they say the higher miles just because you are supposed to constantly add to the engine.

l008com

I do 5000 because its easy to remember. And I find that by 5000 I'm usually down a quart but since the oil change is coming I end up never adding oil. I have a pair of quarts in the trunk just in case though. But yeah if the manual says 7500 and I'm doing 5000, its quite possible even I am wasting my money. I would never bother going below 5000. There is something to be said about the time you save having to deal with half as many oil changes as a piston car.

dannobre

iTrader: (3)

[QUOTE=went_postal]So... Why oh WHY would you use synthetic in a Rotary? That is just bad juju as this car purposely burns oil. From what I understand, synth. will burn but not completely... That being the case it is supposed to cause issues with the engine.

QUOTE]

That is the biggest myth on here...ask RP about that...there is a huge difference in a lot of variables...but they both burn at anywhere near combustion temperature. The synthetic is "cleaner" ..so it burns better..................

DrDiaboloco

Okay, cool. Why don't you just change your oil every 5,000 miles and send me the check for the $30 oil change that you're skipping at 2500 mi?? I will personally guarantee you, on pain of engine replacement, that your engine will easily make it past 150,000 miles with no engine oil-related failure.

I'd love to pocket that $600. I sure plan to.

Hey, using your logic....

If you're bitching about the cost of oil changes you shouldn't be buying a 30k sports car, change it every 200.

Why are you being a wuss and only changing it every 2500? You know the oil manufacturer's/Mazda's interval is BS... Change it every fillup of fuel, actually. If you can afford a 30k sports car, you should stop bitching and change the oil every 200 miles.

Hey, makes sense using the arguments around HERE, certainly. Hell, why not change it every time you DRIVE it? It makes as much sense as changing it every 2500 miles. Clearly you can afford it if you drive a 30k sports car. *sheesh*

You show me a valid, scientifically-based (as opposed to BS "I know it to be true") reason to change prior to 5000mi and I'll do it. Until then, you can just send me that check.

DrDiaboloco

Dare I ask why you don't simply ADD oil when the oil level drops to "close to the bottom line on the dipstick"?

I've been through this already with a former car of mine which drank far more oil than an RX-8 could ever hope to... About four quarts every thousand miles. To do an oil change on a car that slurps oil and needs constant replenishment doesn't make a whole lot of sense... The oil that gets drained at 3000mi will be practically new and nowhere near its' service life.

Hey, if it makes y'all feel better to change oil at 2500mi or whatever, go ahead and fork over your money to the oil companies to your heart's delight. By my reckoning, I'm doing enough of that already every time I go to the pump.

dannobre

iTrader: (3)

As long as you change the filter in the above example...I have no problems

There are lots of reasons for changing oil more often than every 5K miles..................

I change mine before every track day....sometimes twice a month.......I figure that if I'm only getting 6 mpg that it must stress the engine a bit more than everyday driving

Krankor

I am most decidedly in the every 5k mile club. In piston engines, I've had excellent results with it, and nobody has managed to convince me that the rotary will be especially different in this regard.

yiksing

Check your oil not just by sight but by feel as well, if it feels a bit gritty its time to change. It is not advisable to leave your oil reduced to the bottom level of the dipstick, more (not over filled) oil means more capacity for cooling.

Krankor

Give me a break.

DrDiaboloco

6mpg!?!?

Yikes!

dannobre

iTrader: (3)

^^ Welcome to the rotary at the track ......

Smileynh

I don't know. My other 2 cars are both high mileage 120k and 105k. At 3000 miles the oil gets dirty plain and simple. Maybe it's just because I live in a colder region but going from -5 to 200 degrees over and over breaks down the long molecular chains in the oils that keep everything lubed up.

It's not the oil itself that breaks down but the polymers in it used for Multigrade oils ie. 5w20 blah blah blah, see below.

"Multigrade oils typically begin as base oils, such as 10W. Then viscosity-index modifiers (polymers) are added in an effort to stabilize the viscosity. This allows a 10W40 oil to flow like a 10W at cold temperatures and a 40W at higher temperatures.

The multigrade oils' viscosity modifiers are long-chain molecules that lessen the change of viscosity with temperature variance. In the past, the polymer additives (used to thicken the oil) were sometimes susceptible to viscosity loss. Permanent viscosity loss occurred when high shear forces (such as the relationship between the main bearings and the crankshaft) actually break the polymer molecules into less-effective smaller pieces. On a similar note, temporary viscosity loss also occurred when the polymer molecules aligned themselves in order to create a path of least resistance.

Fortunately, today's additive packages have improved oil's shear-resistance. However, oils with the same rating from different manufacturers can exhibit different viscosity ratings in an operating engine, depending on the shear stability of their viscosity-modifying additives.

For technoids, weights are defined thusly (stokes and centistrokes are measurements of viscosity):"

Additionally:
The extended oil drain intervals given by the vehicle manufacturers(typically 7500 miles) and synthetic oil companies(up to 25,000 miles) are for what is called normal service. Normal service is defined as the engine at normal operating temperature, at highway speeds, and in a dust free environment. Stop and go, city driving, trips of less than 10 miles, or exterme heat or cold(NH Driving ) puts the oil change interval into the severe service category, which is 3000 miles for most vehicles. Synthetics can be run two to three times the mileage of petroleum oils with no problems. They do not react to combustion and combustion by-products to the extent that the dead dinosaur juice does. The longer drain intervals possible help take the bite out of the higher cost of the synthetics. If your car or bike is still under warranty you will have to stick to the recommended drain intervals.

-- SmileyNH

rx8wannahave

I'll just hit the middle ground...

Not 2.5K

or 5K

I'll do the 3ish interval so I can sleep at night, lol. By the way...I don't put alot of miles on my RX8 so do you all mean x miles with complete disregard for time (3 months)? Should miles be the only concern when you change your oil or should the amount of time between oil changes be factored in???

My first ever oil change was at 4-4.4K and my 2nd was around 6.5+K because I obeyed the dealer sticker on my windshield (lol).

So...do you all factor time into this also?

RX8_GT

Although I'm a 2500er - I'm not totally sure about time. At least once or twice a year.

I change the oil in the Miata in the Spring when the hardtop comes off - than in the fall when it goes back on. Only 3 to 5 K per year - but it 'lives' outside under a carport. Driven once or twice a week at least.

The other cars including the RX-8 get 8 to 12K per year - so 3 to 4 months.

saxon987

I bought my 8 about six weeks ago, and I'm going to do the first oil change this week, at about 1500 miles; then every 3000mi/3mos thereafter.

I'm also going to have them check the engine-controlling software to see if it is up to date. Although I bought the car new six weeks ago, it was manufactured in April '04. I am hoping (small hope) that a software update might improve the MPG.

saxon

Cooder

Read EVERY word in my post. I don't think it was a low oil issue. I think it was about dirty oil. The oil was clearly dirty on the dipstick. My mpg went down, but I don't think it was because their wasn't enough oil; I think the mpg went down because there wasn't enough clean oil. Adding a quart of oil wouldn't increase the relative amount of clean oil that much.