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Been looking around on the forum and through the many threads know I definitely need 75W90 GL-4 gear oil for the flush. No mazda dealership around me sells it bottled its bulk only so I had to buy from a local parts store that gave me Lucas (Mazda said they use Quaker). Just want to make sure the oil will work properly. Its a full synthetic that's says GL4 GL5 like it has properties of both?? Is this safe for my 8?
I know this thread has probably run its course, but there's something I didn't see emphasized enough or explained fully here, and I think it's important.
If it says GL-5, it's not good for the trans, no matter what else it says.
GL ratings are not about compatibility. They are about extreme pressure (EP) performance. Any oil that meets a given GL level also meets the ones below it, which is why so many gear oils list more than one GL level.
The diff has a lot of EP going on, so it needs GL-5. The trans doesn't.
The problem with GL-5 oils is that they tend to have higher levels of EP additives, which tend to be corrosive to synchros. If an oil lists GL-5 at all, that means it has that higher level of EP additives, which means it's probably not as good for the synchros as an oil that only meets GL-4.
Thank you, I did end up going with redline gl4 oil for my trans but I appreciate the clarity for anyone else that may not have understood the rating system.
Always verify - three Mazda dealers (two in Cincinnati, OH and one in Greensboro, NC) were willing to put GL-5 in my MT of my 2010 RX-8 GT. Dealers simply didn't look to what the car required - they stock one drum of MT lube and it was GL-5 grade.
Just go to a Ford dealership, or call first, this is the only one I'll use now:
Motocraft XT-M5-QS
Just changed out the old oil to this liquid gold ($23 per litre). 3rd and 4th fear are quiet now and shifting is better. Wish I’d taken a photo of the slug of material on the drain plug.
Just changed out the old oil to this liquid gold ($23 per litre). 3rd and 4th fear are quiet now and shifting is better. Wish I’d taken a photo of the slug of material on the drain plug.
How long had the MT90 been in your car before you switched to the magic Ford elixir?
My factory fill was pristine when I changed it out at 44K miles to MT90. Been going strong on MT90 now at 55K miles.
I’ve no idea as I’m probably the 4th owner. Had 96,000 km when I bought it and by the look of what came out I’d guess I was the 1st one who cared to change the fluid. There was a substantial slug of material on the drain plug. Shifts well now but, might be worth changing again in the spring.
I saw the same thing when changing the differential fluid that was supposedly fresh prior to me buying the car.
Here’s what magnetic drain plugs from my differential and transmission on my S2 looked like after 10,000 miles of mostly track use with red line oils. Top picture is diff and bottom is transmission drain plug. Diff plug did not have nearly as much metal as transmission plug did :-(
Last edited by Nadrealista; 10-30-2020 at 11:32 AM.
My transmission drain plug was less of a slug plug but, similar. Noticed during the test drive with previous owner the down shifts were reliant on the synchros with no throttle blip. Might have been hard on the internals. I’ll stop now cause I might be jinxing it
10-08-2017, 05:34 AM
