Public Lab Research note

Oil Testing Kit -- discerning 5W30 20W30

by gretchengehrke | July 10, 2015 15:59 10 Jul 15:59 | #12046 | #12046

What I want to do

I am taking spectra of the five oils in the Oil Testing Kit, and I forgot to label one of the cuvettes. Based on color, I could not determine if it was 5W30 or 20W50, so I compared the fluorescence spectra with hopes that they would have different lambda-max values.

My attempt and results

All three of these spectra were taken using a Blue Ray 405nm light for excitation, moderate light attenuation, and calibration based on the spectra of my white front bike light. The spectra have been smoothed and the peak heights have been equalized.

The spectra between the known 5W30 and 20W50 are sufficiently distinct, and the unknown aligns with 20W50.

Questions and next steps

How repeatable is this resolution? How comparable will the spectra be if I calibrate using a different white light? How will they compare if I dilute them? Will I be able to observe two peaks at the appropriate lambda-max values if I create a mixture of the two oils?

Why I'm interested

We want to know the precision of the spectrometer and our ability to discern different grades of oils in the real world. We're starting with neat samples and moving to mixtures and real environmental samples.


wow! that's a real clear match!

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Hmm, how did you use your white front bike light to calibrate? Surely it's not a compact fluorescent bulb?

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