Johnson Suzuki 225 4-stroke Engine Oil?

May 6, 2011
New to boat maintenance so I knew to come here first for the engine oil. Here is the suzuki spec:
Suzuki oil meets the National Marine Manufacturer Association (NMMA) Four Cycle Water Cooled (FC-W) standards. The actual oil recommendation is: SAE or NMMA FC-W 10W-40 (operating in temps from 14 degrees to over 100 degrees F) or 10W-30 (operating in temps from -4 degrees to 86 degrees F) API or NMMA FC-W Classification SE,SF,SG,SJ. For temps below -15 degrees F use SAE or NMMA FC-W 5W-30.
I'm seeing some discussion about Diesel oil. Any recommendations there? I'm in the South Carolina so want to cover the high temp range. I also run the full rpm range - up to 6000rpm every now and then so want something that isn't going to foam. Any knowledge appreciated. I like buying my oil from Walmart but I don't want to cheap out if it's a bad idea.
Diesel oil is what the engines use for fuel...The HDEO oil are more resistant to foaming than passenger car oil since the advent of Caterpillar's introduction of the Heui fuel injection systems. I doubt foaming is an issue with any of todays oils from a quality bottler.
Originally Posted by CT8
Diesel oil is what the engines use for fuel...
First off, thank you - but what do you mean here?
Is it still under warranty? I have a merc 95 hp and I use the marine rated full synthetic mystik oil. cheap, synthetic and marine rated, what else can a man ask ;-) if you idle a lot, change often, mine makes oil when I idle or troll at idle (michigan salmon fishing for ya)
Used this in my Johnson/Suzuki 115, OMC Synthetic 4-stroke outboard oil allows you to go 200 hours between changes.
Originally Posted by ItsMeHank
Originally Posted by CT8
Diesel oil is what the engines use for fuel...
First off, thank you - but what do you mean here?
It's an unhelpful reply. Diesel oil can mean fuel, but in this context you clearly mean motor oil meant for use in diesel engines. Back to your question, the mfg recommendations in your first post suggest using Suzuki oil but what it boils down to is that any modern passenger car motor oil that is the correct weight is fine. The "s" ratings (API Service) are pretty lenient. The current standard is "SN" and if "SJ" is sufficient "SN" is fine. So if you want to buy at Walmart, I'd do the Supertech full synthetic if you can find it in the correct weight. Regarding the diesel oil - 15W-40 is a common weight for motor oils specifically marketed for diesel engines, such as Shell Rotella. I'd just run a gasoline passenger car oil personally.
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A couple years back a Suzuki mechanic posted a warning over oil foaming. He demonstrated with a twin engine offshore boat that after a long run with one engine using PCMO and one on NMMA oil … you could actually pull dipsticks and see for yourself. Unfortunately he did not do the test with HDEO … he left one with what the client used and one FC-W. This would indicate you could run WOT and check the stick on whatever oil you go with. Think either is fine, and buying HDEO for such a good price can be conducive towards more frequent changes. I only buy two quarts a year, so just stick with FC-W at this stage …
Originally Posted by gotnogunk
Agree with STOCKREX- Mystic if you can find it, if not a good HDEO
I have posted Mystik JT4 specs here before … Looks solid … even a really good Noack.