General Quality Check

Part 1.

Collect a sample from the tank’s bottom area by draining some fuel off, or by using a Bacon-Bomb type sampler device or a extractor pump available at most auto parts stores.

Part 2.

Inspect your sample visually by swirling it in a clear bottle or jar. Look for water and dirt settling at the bottom as you swirl.
– A few drops of water indicate a water issue.
– If you notice material resembling what looks like coffee grounds, it’s a sign of biological growth.
– The presence of slime or algae-like substance also signals biological growth.
– If your diesel is bright and clear, it’s in good condition.
– If the fuel is a darker color but still clear, it indicates some aging has taken place, you should consider using the fuel or by replacing it within the year.
– A dark fuel with a “hazy” color appearance that is hard to see through suggests aging fuel and can be sent to a testing lab to check for:
– Oxidative stability to see if it’s aging beyond specification.
– Biological growth indicating microorganism presence.
– Water content suggesting excess water accumulation in the tank.
– Dirt or rust content indicating potentially other issues.

Biological Growth Check

Obtain a fuel sample that appears in “excellent health” and store it in a warm and dark place for a month, daylight can kill most biological growth in fuel so fuel must incubate in a dark atmosphere.

After 30 days:

– If you observe a film or darker layer in you sample, biological growth is occurring.
– If no changes are visible and you’re curious to test a little more, add about 5 ml of water to the sample, shake it, and leave it a warm and dark place again. Re-examine it after another 30 days:
– A new darker layer on the surface where water meets the fuel indicates growth in your tank is very possible.
– If no growth occurs, your fuel is stable and even if water has infiltrated into your fuel it remains ready for use.
Note: Always remove water from your tank using additives, absorbers or by draining. Over time water will cause complications and promote growth.

Notes:

This test is not a replacement for a diesel fuel test kit or a laboratory analysis like CAT SOS. This is a DIY hack for general diesel fuel testing that will cost you nothing.