Eneos 75w-90 Transmission Oil Test:

In the course of using various fluids for the RX8 over the past 6 years, Black Halo Racing found the Eneos 75w-90 GL5 manual transmission/differential gear oil to be one of the best oils we have ever used in the Mazda RX-8.  The oil produced very smooth shifts and was capable of handling the abuse we've put our own cars through, both on the street and at the track.

Rumors have circulated for years in the RX-8 community that the new GL-5 transmission fluids are harmful to yellow based metals like brass or copper.  (Manual transmission synchronizers are made of these metals.)  That may be the case with other GL-5 fluids but read on for the results with Eneos.

Black Halo Racing enlisted a professional lab to analyze the Eneos fluid before BHR would recommend it to our customers.  After 8,000 miles of daily driving in the hot Phoenix summer, a sample of the fluid from one of our team cars was sent to BlackStone Labs in Fort Wayne, Indiana.  Blackstone specializes in oil analysis and are highly reputable in the petroleum industry.

The report listed below shows that after several thousand miles there are no significant amounts of dissolved yellow metals in the transmission fluid.  The high aluminum content is from the aluminum shift forks in the Aisin transmission which is used in the Mazda RX-8, and is normal for this transmission.

The report listed below is after a sample taken with 17,000 miles on it.