Today I changed the oil in my '06 Toyota Matrix 5-speed at 21K miles.
The owners manual calls for 75W-90 GL4 or GL5, so I used Valvoline 75W-90 GL5 oil.
It really needed changing as the oil was dark with a metallic sheen, and these trannys have had a number of early failures (60-100K mi.)
I mentioned this on a couple other forums and someone said using GL5 will mess up my transmission because of high sulfur content.
I checked back at the nearby auto parts store and they had no GL4 oils.
I could find no mention of this on Toyota or Valvoline’s websites.
I google searched and found some conflicting opinions.
I’m hoping an expert like Transman will give me the straight dope.
Does GL5 supersede GL4? Should I seek out GL4 and change the oil again?
p.s.: The Valvoline is also MT-1 rated.
Just like motor oils, gear lubes have a service rating. Motor oils have an SM service rating at this time. This service rating superceeds the previous service ratings. So if GL5 is used instead of GL4, you’re using a gear lube the American Petroleum Institute says is better, and the Society of Automotive Engineers agree with.
Tester
GL5 replaces GL4. Failure of manual transmissions is seldom lubricant related. Did the drain plug have a magnet built in it? Gearboxes can benefit by having a magnet inside them…
How about some comments from the “day shift”…
If you want to obsess about it, you can take it to bobistheoilguy.com where they have an entire section devoted to gear oil…
CircuitSmith…
I find it quite interesting that they mention both the GL4 and GL5 interchangeably. My understanding is that they are quite different, as you have mentioned re. the sulphur content in the GL5 and how this affects the brass synchros. Do you happen to have the Factory Service Manual to crossreff what they say in there?
My 2000 Nissan Altima says it needs a GL4 oil and I have been using the RedLine Synthetic MT-90 75W90 GL-4 in it since 2002 with very good results. You might want to check it out here:
I have also been using RedLine GL4 Tranny oil in my 1986 Golf GTI since 1990 with no issues at all. My shifts into 2nd gear are still buttery even after 225k miles 
Personally, I would rather use a straight GL4 oil than risk messing up the synchros with GL5.
CircuitSmith…just as another data point for you.
I just went and checked the Factory Service Manual for a 1996 Toyota Corolla. They list as manual transaxle oil lubricant: API GL-4 or GL-5 SAE 75W-90; 2 quarts total.
So, after all perhaps you are indeed OK with the GL-5 you put in. However, I am not sure if the tranny model they used in your 2006 is the same is the one in the 1996. They do not specify anywhere the manual tranny model/code for it.
You stated that the manual says GL-4 or GL-5. So the real question is why don’t you believe the manual. I would think the Toyota engineers know better than “some people on other forums”. If I used what the manual specifies I wouldn’t sweat it at all.
“So the real question is why don’t you believe the manual.”
Well, I do believe the manual. I don’t plan to change it out if it has good shift feel.
I’m still curious about what others on this forum have to say.
“I just went and checked the Factory Service Manual for a 1996 Toyota Corolla.”
I would think that after 14 years Toyota would have put something in the books if not all GL5 oils were OK.
GL5 in the past would etch brass synchros due to sulfur content where GL-4 would not. If it is also labeled MT-1, it is safe to use.
Google “MT-1 lube brass synchros”
This is very true. I use GL4 in my TR6 as the newer GL5 will wreck the synchros in the gearbox.
In SOME vehicles you can NOT use GL-5 if GL-4 is called for. GL-5 contains Sulfur. If the transmission has any brass components…the sulfur will eat away at the brass. If the tranny doesn’t contain any brass then there won’t be a problem…Since Toyota says using GL-5 is ok there probably isn’t any brass in the tranny. My 98 Pathfinder had brass in the tranny and Nissan gave plenty of warnings about NOT using Gl-5.