It appears to be chrome.

 

The gas cap is chrome...what are you talking about?

 

I love how I got thread jacked.

I've decided I'm going to go with Redline MT90 transmission oil, Redline 75w90 for the differential, and Royal Purple Synthetic 5W-20 for my engine.

I understand that Mazda doesn't recommend the use of synthetic oil but after reading through some threads on here, I don't think it's an actual problem. However, can someone recommend me a cheaper alternative to RP? It's a tad expensive.

 

mobil1 instead of RP. always use 5w-20 and make sure the oil is ford spec. that means it has the same specs needed by mazda for the rotory. right now im using castrol synblend. so its a bit of both oils. how much is it to change the differential?

 

Thanks for the suggestion. I was also considering Mobil as well.

As for the cost of a differential fluid change, unless I'm mistaken, I will need two bottles of Redline 75w90. I honestly haven't been shopping around for prices yet because I don't quite understand the procedure just yet. I'm guessing it shouldn't be anywhere near over 50 bucks if you do it yourself.

 

^ Yes, you need two quarts. A quart hand pump (same one used on marine outboard motors) is handy. Picture of pump (but buy much cheaper at Pep Boys): http://www.928motorsports.com/parts/oilpump.php

Just jack up the rear at the differential fins and then place outboard jackstands and you'll have plenty of room. Actually best to have front jacked as well so as to assure level filling..... and if you have the front in the air you may as well change your manual transmission oil (Redline MT90; 2 quarts also).

There are good DIY instructions/pictures here and elsewhere.

http://www.5cats.org/rx8/trans_diff_refill/

http://www.hi-impact.org/ryang/modif...x8_fluids.html

 

This is EXACTLY what I needed. Thanks a lot! Yeah, I'm planning on changing my transmission fluid as well, its just more convenient that way.