Hello,
We are trying to reuse oil by re-refining the used oil using "Acid Clay Process". We treat the used oil first by sulphuric acid. Then we used the activated clay to deodour/decolorize the oil.

The final product is fine but after exposing it to sunlight the color turns dark. We suspect it is due to some impurities still present in the oil. Can someone please guide us what could be done to get this problem fixed.

Note: We cannot use distillation as we are doing this on a very small scale.

Thanks