To clarify, the 7 month old fluid in my car measured 5mV (0.005V).
I tested the darker 18 month old fluid in my motorcycle today and the reading was 25mV (0.025V.)
The reading fluctuated, starting high at 50mV and then falling slowly to 25mV. I am using a digital meter set on the 200mV range so the input impedance should be reasonably high but it still seems to have an impact on the reading. The depth of insertion of the probe also caused the reading to fluctuate which I suppose is what you would expect.
It seems I have a long way to go before reaching 0.3 V and will check again when the fluid is 2 years old. I'd have to say I'm not yet convinced that it's a reliable test particularly the 0.3 volt threshold.
I tested the darker 18 month old fluid in my motorcycle today and the reading was 25mV (0.025V.)
The reading fluctuated, starting high at 50mV and then falling slowly to 25mV. I am using a digital meter set on the 200mV range so the input impedance should be reasonably high but it still seems to have an impact on the reading. The depth of insertion of the probe also caused the reading to fluctuate which I suppose is what you would expect.
It seems I have a long way to go before reaching 0.3 V and will check again when the fluid is 2 years old. I'd have to say I'm not yet convinced that it's a reliable test particularly the 0.3 volt threshold.