In general, the major marine engine designers require a full scale ship trial lasting a minimum of 4,000 running hours (about one year) to be conducted in order to approve a lubricant. Engine designers approve only formulation specific lubricants; blanket approvals for additives are not available. However, rebrand approvals, which allow the an approved formulation to used by another manufacturer under their brandname, are possible and are often specific to each Original Equipment Manufacturer (OEM).

For two-stroke (slow speed) engines rebrand approvals are granted by:

  • MAN Energy Solutions
  • WinGD
  • Japan Energy Corporation

For four-stroke (medium speed trunk piston) engines rebrand approvals may be possible to obtain from:

  • MAN Energy Solutions
  • Wärtsilä
  • Caterpillar MaK
  • MTU

The lubricant approval process

Although approval process differs between OEMs and whilst their lubricant validation processes continue to evolve there are some common characteristics. The general process may be thought of as following the following steps:

  • Oils are evaluated and screened in chemical and mechanical laboratory bench tests, The results of this testing is then presented to the OEM and if satisfactory a Letter of Support (LOS) is issued by the OEM. This allows the applicant to approach ship/engine owners to seek a trial partner.
  • The lubricant candidate is then evaluated through a full scale marine/engine field trial which, depending upon engine manufacturer and operating conditions, may last between 1,000 – 6,000 hours.
  • Typically 2 cylinders are opened for inspection at the start and end of trial. Engine operating conditions (i.e. load, speed, exhaust temperatures, fuel and lube oil consumption) are recorded throughout trial and used lubricant and fuel oil analysis carried out at predetermined intervals.
  • At the end of the trial the results are reported to the OEM for approval. If successful a No Objection Letter (NOL) is granted and most approvals are time limited to two years.

For more information on marine diesel engine oils, contact your Lubrizol representative.