Synthetic Gear Oil - Toyota Yaris Forums

CoryM · 09-28-2015, 09:07 PM

I suggest running the OE specification for A/T and M/T. The reason being you have friction surfaces which are designed to work with a certain fluid. If you make that fluid more or less slippery, the friction surfaces will increase or reduce their performance.

In the case of M/Ts, you have synchronizer rings. These are little brakes that use friction to slow the spinning parts down enough that you can change gears without grinding. If you use slippery synthetic oils the syncronizers will not work as well; making it take longer to slow the rotating parts down.

I tried two different synth oils in my Yaris since the shift feel is so bad, and because I'd heard a lot of people on the forum have positive results. I ended up going back to non-synth oil within a few days because I could feel the syncronizers not working as well. The generally accepted life of uncontaminated gear oil is 100,000km to infinity (many OEM suggest there is no need to change). That being said, I have never personally done oil analyses on gear oil.

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09-28-2015, 09:07 PM	#4
CoryM Drives: 2009 5-door, 5-speed Join Date: Sep 2011 Location: White Rock BC Posts: 687	I suggest running the OE specification for A/T and M/T. The reason being you have friction surfaces which are designed to work with a certain fluid. If you make that fluid more or less slippery, the friction surfaces will increase or reduce their performance. In the case of M/Ts, you have synchronizer rings. These are little brakes that use friction to slow the spinning parts down enough that you can change gears without grinding. If you use slippery synthetic oils the syncronizers will not work as well; making it take longer to slow the rotating parts down. I tried two different synth oils in my Yaris since the shift feel is so bad, and because I'd heard a lot of people on the forum have positive results. I ended up going back to non-synth oil within a few days because I could feel the syncronizers not working as well. The generally accepted life of uncontaminated gear oil is 100,000km to infinity (many OEM suggest there is no need to change). That being said, I have never personally done oil analyses on gear oil.