If the fuel percentage in lube oil is 4.0%, which category does it fall into?

• A. Warning
• B. Acceptable
• C. Marginal
• D. Unacceptable

Answer: (A)

Fuel dilution in lube oil shows how much fuel has contaminated the oil, and rising percentages mean the oil isn’t lubricating as well as it should. Categories help you decide how urgently to act. A reading of 4.0% is above normal acceptable limits but not at a level that would mandate immediate, drastic action. It sits in the warning range, signaling you should monitor the oil condition closely and plan corrective steps. This might include probing the fuel system for issues, checking combustion efficiency, considering an oil change, and conducting follow-up analyses to confirm whether dilution is stabilizing or increasing. Not being in the unacceptable range means there's time to investigate and address the underlying cause before serious engine damage occurs.