Black oil in diesel engine

Year of publication: 1999

In our construction company, we operate a wide variety of construction equipment. We also have our own fleet of trucks. All engines are regularly monitored with OELCHECK lubricant analyses. Based on the analyses, we usually change the engine oil at longer intervals than specified by the manufacturer. Now, following a recommendation from our lubricant supplier, we switched to a supposedly higher quality, semi-synthetic diesel engine oil SAE 10W-40, type SHPD. However, after the change, the oil already turned noticeably black in a short time. What could be the cause?

OELCHECK answers:

The black coloration of the oil is no cause for alarm. On the contrary – it clearly shows that the lubricant is doing its job. The faster the oil turns black, the better the oil quality. It has additives that dissolve sludge as well as varnish-like deposits. These contaminants are caused by combustion residues or by other impurities. It is also characterized by good dispersing properties. It keeps the contaminants in suspension and ensures that they cannot form new deposits. In this way, the oil keeps the engine clean and protects it from unnecessary wear.