Well that pretty much answers my question on MPG.

Can you tell the difference from the stock fluid? I guess I am asking is it worth changing?

 

For the extra cost I really dont think it was worth it, Tacomas are hard to shift into 2nd gear when cold and its no different between the Dino and the Synthetic.

 

By all means read the manual:

 

If you look into what metals are in the trans of xBs, you would see that GL5 is NOT the best choice to make. Sure, they will work, but they will also shorten the life of your trans as well. This has been proven.

I stick by my quoted statement....Toyota would much rather just buy and stock 1 fluid (GL5) then place the best possible choice into all service departments. Makes sense in a business fashion, but the 5 will never go into my trans.

 

What metals? How does GL5 oil shorten the life of the transmission, and why would Scion specify it?

 

Most GL5 is a different spec, and is not 'backwards compatible' with GL4.

GL5 gear oil is a lubricant with very high extreme pressure performance needed for Hypoid gears where sliding and rolling contacts operate under very high loadings. This is achieved by incorporating high concentration of sulfurized additives (EP additives). The downside to such high sulfur in oil is it tends to corrode yellow metals, so can ruin parts like brass synchronizers and some bushings, which are in the manual transmissions of Scion xB's. See link at end.

Extreme pressure additives actually act by "corroding" ie, reacting chemically with the protected surfaces. In more severe sliding and loading conditions, as in gears, simple adsorbed or chemi-sorbed anti-wear additives will eventually be inadequate to prevent severe adhesion. If the temperature increase caused by surface friction is too great the adsorbed molecules will desorb and the protective film will no longer be present to prevent adhesion of the surfaces.

Screen shot of email from Scion Corp:
http://i119.photobucket.com/albums/o...2006/mt/mt.jpg

As for why, I already answerd that…its cheaper to stock one kind of GL than two. Simple economics. Again, GL5 wont cause your transmission to fall apart, but it is not the best choice. If you are like a lot of people and only plan on keeping it for 5 years or less, than it really does not matter what you put in there. Im sure most wouldn’t even change out the factory fill, let alone do it at 10K miles like I did. But if you want the best for your box, GL4 is the only choice.

I changed out my GL5 and put in synthetic GL4, Redline MT90 to be exact. There is a very noticable performance increase between the two…smoother, quicker shifting…almost "falls" into gear w/ GL4. A lot has been said about the RL MT fluid on this site..a simple search should yield some good info. Additionally, the Mobil syn. GL5 has had poor reviews on this site.

 

Same here, a year ago.
http://s49.photobucket.com/albums/f2...0Oil%20Change/

 

I changed out a Reverse Light Switch on my Cavalier and I see it uses ATF in the Manual Tranny too!