Oil Requirements for Gasoline Engines and Preventing
Contamination of Engines with Emissions Control
Models Affected
Model Serial Number Range
Gasoline Sterndrive All
Gasoline Inboard All
Gasoline Tow Sports All
Gasoline Sterndrive with Emissions Control All
Gasoline Inboard with Emissions Control All
Gasoline Tow Sports with Emissions Control All
Situation
The following crankcase oil recommendation includes newly available engine oils, and
supersedes all previous crankcase oil recommendations for MerCruiser gasoline engines.
This service bulletin contains the best available recommendation from Mercury Marine as
of February 2008. If the owner's manual, which is updated from time to time, is not
consistent with recommendations made in this bulletin, follow the recommendation of this
bulletin.
Newly introduced engine packages with Emissions Control have catalysts that will be
rendered ineffective if they become contaminated with certain elements or compounds.
These packages require special lubricants as described in this bulletin.
Engine Oil Recommendations for MerCruiser Gasoline Engines
For optimum engine performance and maximum protection, use the following oil:
Application Recommended Oil
All MerCruiser engines Mercury MerCruiser Full‑Synthetic Engine Oil, 20W‑40, NMMA FC‑W rated
IMPORTANT: Lubrication requirements for catalyzed engines differ from the requirements
for non‑catalyzed engines. Some marine‑grade lubricants contain high levels of
phosphorus, which can damage the catalyst system on MerCruiser engines. Although
these high‑phosphorus lubricants may allow acceptable engine performance, exposure
over time will damage the catalyst. Catalysts damaged by lubricants containing high levels
of phosphorus may not be covered by the MerCruiser Limited Warranty.
Oil Requirements for Gasoline Engines and Preventing Contamination of Engines with Emissions Control
Page 2 of 2
If Mercury MerCruiser Full‑Synthetic, 20W‑40 oil is unavailable, use the following
lubricants, listed in order of recommendation. If you are servicing a catalyst engine, use
these for short periods of time only.
1. Mercury/Quicksilver 25W‑40 Synthetic Blend, NMMA FC‑W–rated 4‑cycle MerCruiser oil
2. Mercury/Quicksilver 25W‑40, NMMA FC‑W–rated 4‑cycle MerCruiser oil
3. Other recognized brands of NMMA FC‑W–rated 4‑cycle oils
4. A good‑grade, straight‑weight detergent automotive oil according to the last row of the
operating chart below.
NOTE: We do not recommend non‑detergent oils, multi‑viscosity oils (other than as
specified), non FC‑W–rated synthetic oils, low‑quality oils, or oils that contain solid additives.
Mercury Full-Synthetic MerCruiser Engine Oil, 20W-40, NMMA FC-W rated
MerCruiser/Quicksilver 25W-40 Synthetic Blend, NMMA FC-W rated 4-cycle MerCruiser oil
Other recognized brands of NMMA FC-W rated oils
SAE 20W
SAE30W
SAE40W
AIR TEMPERATURE
ORDER OF PREFERENCE
(32° F)
0° C
(50° F)
10° C
32878
Mercury/Quicksilver 25W-40, NMMA FC-W rated 4-cycle MerCruiser oil
Preventing Contamination of the Emissions Control System
Catalyst and oxygen sensors can become contaminated, leading to component failure.
Phosphorus, found in some marine‑grade oils, and other compounds will damage or
destroy a catalyst's ability to clean the exhaust. Catalyst‑friendly oil, like Mercury Full
Synthetic MerCruiser Engine Oil, prevents this damage. Approved synthetic oils must be
used in MerCruiser engines with emissions control.
Acetoxy silicone sealants and other compounds in the exhaust stream can damage oxygen
sensors and catalysts. Do not use non‑approved compounds and sealants. Oxime silicone
sealants and Loctite 587 High Performance Blue can be safely used with catalyzed
engines.
Fiberglass, a silica‑based material, can contaminate the catalyst and the oxygen sensors.
To reduce the possibility that the engine will ingest harmful fiberglass and thereby poison
the emission control components, protect the engine from fiberglass dust and debris during
construction and clean‑up.
