The 09 manual has listings for front and rear, and the rear (only) shows synthetic. Not sure why they would be different between front and rear, or why an 08 wouldn't be the same.

 

I wonder if you are looking at the G37X, the 4WD model.

No one at Infiniti of America is aware of a change in the rear diff fluid of a G37S from 08 to 09.

 

The 09 manual specifies differential hypoid oil in the front, and synthetic in the rear...regardless of which version. There is only one recommendation for each end. Not sure why there would be any difference in the 08 - maybe yours came with synthetic in the rear and the manual is off, or they just made a running change on the 09s. BTW - this manual is about the worst written new car manual I've ever seen, and it's not all up to date for 09.

 

That's my point. There is no front differential in a rwd car. If you are looking at something referring to a front differential, you are looking at something referring to an awd car.

The G manual covers all versions of the G. That's why a number of coupe owner members followed the manual and tried and tried to get the front seat to retract backwards when they wanted to exit the car. That feature is a sedan-only feature. But, it is still in the G manual. It is not applicable to the coupe. I think the part you are reading is applicable only the G37X and not to the rwd G's.