RR analysis for a brake fluid filling process

You want to know how well you can captur the variation in your fill operation across your specification range.Make up 10 samples that cover the span of your +/- specification, using pours from granuated beaker in your lab, or whatever way to have to get the amounts close (you are measuring R&R, not accuracy).The next step depends on whether you have actual manual operators, or if this is an automated measurement.

Repeatability : when the same parts are measured multiple times by the same operator . Reproducibility when the same parts are mesured multiple time by different operators.When you say that each part is different and there is no way that it can be meausred twice by the  same or different operator . I think a destructive GRR is appropriate in this case.
Just a suggesation !!

Hector –
I would look at performing an Interclass Coefficient Correlation (ICC) study.  You can look information up by Don Wheeler you could also send me your email and I could get you an excel worksheet that explains it.  What you primarily are doing is comparing the variation of a known standard with what you are measuring and see how much variation is attributable to measurement error either through the system or the gage – dependingon how you run the test. 
You would take the reading off of your machine and then compare it to the amount you are getting out each time.  Easy test to use.  Works well in a lot of situations including things like inventory and transactional studies.