After how many miles does Mazda recommend we change our oil? I can't find my manual already :p

 

7500 i think, but do NOT follow that. My mazda dealer recommends 2500

 

Mazda's recommendation is 7500 miles for "normal" driving, 5000 miles for "severe" conditions.

 

You would think that a motor that revs as high as an RX-8's would require more frequent oil changes, not less. How come its so high? I think I'll go with 5000. Its a nice round number, plus, its a lease so who cares ;-)

 

My figuring is that it is because of a couple of factors. There is a large volume of oil in the system, over 7 qts, which provides a lot of volume to dissolve contaminants, etc. In addition, there are far fewer moving parts and bearing/wearing surfaces in the Renesis compared to a typical piston engine. There's the two rotors with their internal ring gears and bearings, and the eccentric shaft and its bearings - that's mainly it. No rod bearings, wrist bearings, cam bearings, lifters/followers/rockers, valve guides, timing set, etc. So, there's a lot fewer bearing surfaces to beat up the oil. Of course, this is just my opinion...

 

Also, what about the fact that it's burning oil and you have to add some before oil change is due. Oil in there is never truly old if you have to keep adding every once and a while.

 

What puzzles me is the gasoline getting in the oil. That cuts viscosity like crazy - anybody balancing that by using heavier grades when adding oil between changes? Also, my dealer recommends changing the oil at 3750 miles. I asked why and he could not say. Considering that no dealer ever did engine tests on cars, they cannot possibily have any real clue as of when to change it. The same dealer recommends the same oil change interval for all Mazda cars - that alone says something about its "knowledge." I'll change the first one around 3500 miles (due to breaking in) then every 5000 miles (though car is far from experiencing severe driving). Mazda did test the parameters to come out with changing intervals - build-in are extra precautions (maybe few thousands miles). Under these conditions, there is no reason what-so-ever to change oil at less than 5000 miles - unless the car is having some major engine problem (i.e., a lot of gas leaks in the oil or combustion products - but then one needs much more than an oil change...)

 

I did the first one at 2500 to clean the new build stuff out and now its going to be ever 5000.

 

I'm sure most salesman just spout off 3000 because its the standard, and it "can't hurt" doing it that often. I'm just going to stick to 5000 cause its easy to remember and stuff. That reminds me I was going to check my level today and I forgot. It would be nice if this car had not only an oil pressure gauge, but also an oil level gauge.

 

According to the owner's manual, crankcase capacity with an oil filter change is 3.7 quarts, not 7. That's not a whole lot, but there really isn't much to lubricate compared with a piston engine. How quickly does the Renesis burn oil, anyway? I haven't checked it yet, but I'm getting paranoid.

 

More profit for the dealer I'm sure. I'd trust the Owner's Manual which was written based on input from Mazda engineers I presume.

Personally, since I have free maintenance for 4 years, I'm having my oil changed every 5k miles.

rx8cited

 

At 1300 miles my car had burned no oil. At 2500 first oil change. Now at 3500 miles and no oil burn.It was checked by the dealer all 3 times.

 

Total engine oil capacity is 6.1 / 7.1 US quarts for standard / hi-power engine. Only 3.7 quarts comes out during an oil / filter change because of the oil remaining in the oil cooler(s).

My engine consumed about 0.5 quarts / 1200 miles prior to the M-flash. It appears to be consuming less now.

rx8cited

 

Interesting. How did you find that out? I can't find it in the book.

 

That doesn't seem right though? When you get an oil change your only changing a little over half your oil?

 

I'm here to tell you it's true. Source is the RX-8 Workshop Manual and it's also been previously posted and discussed. My oil does not "look" dirty after 5k miles, so I'm okay with it.

rx8cited

 

Unless the filter is broken, oil cannot be dirty. Once it plugs, it filters even better. The size of solids going through is too small to see with naked eye - unless is agglomerates for some reason. It can look dark, but that is different. Components inside do oxidize to protect more important ones. The main reason one changes oil is lost viscosity. Both gasoline dilution and higher RPM/temp. the Renesis generates will break down oils faster. The 5W20 recommended in US does not have a lot of visc to start with. That helps mostly at start-up cause oil moves faster to lubricate parts. I guess it is hard to find a good compromise... so I will be getting the dealer oil change (5W20) and add 10W40 in between - to make up for viscosity loss. I need about 1/2 qt. at 2000 miles, BTW.