Recently I went to order a set of these 100uF electrolytic capacitors with 10% tolerance, needed for impedance balance for an audio output. When I noticed they were out of stock, I decided to order a number of the 20% version, thinking I could just measure them and sort out the "beyond 10%" tolerance caps. To my surprise, when measured with my Fluke 87V (DC), all caps measured just about the same at around 103.4uF (I expected them to vary as resistors would). This was more-or-less the same value I measured on most of the 10% caps. The datasheet specs the capacitance tolerance at 120Hz. I've also read that DC measured capacitance is often around 10% higher than the AC measured capacitance.
So my questions: Are actual electrolytic capacitance values generally relatively consistent across a wide frequency range? For example, can I pretty much assume that if the capacitance is 102uF at 20Hz, that it will be around the same at 20kHz? (Related to this, should the datasheet tolerance spec be read as the deviation of capacitance from the specified capacitance, independent of frequency, or does it also account for frequency dependence)?
Secondly, does the consistency of the measured DC capacitance across a number of different capacitors give me any indication of the consistency of actual capacitance values in AC? In other words, is it likely/probable that while all the caps measure the same at DC, that they could deviate significantly from each other at, say, 1kHz, with one cap measuring 85uF and another 105uF? Or can I assume that if the DC readings are all pretty much the same, the AC readings should be also?