In some applications, the higher viscosity is beneficial for reducing 1-2 shift grind, but the OE specification calls for a 75W-80 or 75W-85 viscosity. The use of a higher viscosity than OE does improve shift quality as a thin fluid was chosen for fuel economy purposes, but going too thick will cause shifting to get more notchy.

The friction modifiers in the oil make a big difference as well.

 

Is there a post ( instruction/pictures)on the site regarding the procedure of changing the manual transmission fluid? I have the exact Cruze as jwhitt72. I did the automatic transmission fluid on my daughter's vehicle and it went well, but I've never changed the fluid on the manual transmission.
Thanks for the viscosity information.

 

Check the tutorial library and there is one. It's as easy as changing engine oil.

 

I don't think the AMSOil synchromesh has impacted my fuel economy. My tires had a lot more impact but there wasn't any noticeable impact from the AMSOil synchromesh.

 

:iagree:.......on both counts!

 

I changed mine with Redline 75w80. No grinding, smooth shifting. Also, if anyone thinks using different weight, but correct for vehicle, oils is going to make a noticeable impact on economy you're kidding yourself. It's difference is lost in the noise of other, bigger factors (driving behavior, tires, wind, etc). Shifting performance and grinding due to different oils is a different topic.