View Full Version : Synthetic Outboard Oil
01-19-2012, 09:39 PM
I just purchased a new 25 hp 4-stroke Suzuki outboard. the manual calls for 10W-40
oil. since it is a new engine I wonder if I should use synthetic oil rather than conventional? the owner's manual is silent on the subject.
I have never used synthetic oil.
any recommendations out there?
01-20-2012, 11:34 AM
Back when Mobil 1 came into widespread use, the conventional wisdom was to use nothing but synthetic oil from Day 1, instead of changing later.
Of course, things have changed since the 1970's. I, too, will look forward to the 'best' answer.
01-20-2012, 08:22 PM
I'd vote for Synthetic in general, and Mobil 1 in particular.
Personal experience... I bought a new Geo Prizm (Toyota Corolla) and used Mobil 1 after 10k miles. The motor was still going strong at 340,000 miles when I got in an accident that took it of the road. I do all of my own maintenance and the two times I had the valve cover off to replace the timing belt I was in awe of a few things. No sludge at all, how everything was coated in a nice thick film of Mobil 1, and that the valve lash did not change .0005 over time. These motors had solid bucket lifters with shims for adjustment. After having a Ford Escort where the cam actually wore through the shim and the top of the lifter I was pleasantly surprised.
If you start with Mobil 1 you may never break your motor in. The crosshatch on the cylinder walls may never seat and you will always burn an excess of oil. 10,000 miles in my auto engine on conventional broke it in fine. What that translates into outboard usage I don't know.
Don't use the High Mileage sythetics. AFAIK these have a solvent in them to swell rubber seals to avoid leaks in older motors that were run on conventional. You will only cause undue wear on your brand new seals.
The big plus I see in a sythetic in a outboard that is likely to be idle much longer than an auto engine is that the film stays much thicker and longer which is a big plus for start ups and corrosion protection over time.
01-21-2012, 04:46 PM
...If you start with Mobil 1 you may never break your motor in. The crosshatch on the cylinder walls may never seat and you will always burn an excess of oil. 10,000 miles in my auto engine on conventional broke it in fine. What that translates into outboard usage I don't know...
Sounds like the outboard equivalent might be to run on conventional oil for X hours (until the first recommended oil change), then switch to Mobil 1.
I'm assuming that the motor will be broken-in after X hours. If not, just use conventional oil until you have enough hours to achieve break-in, then switch???
Peter Malcolm Jardine
01-21-2012, 05:34 PM
Engines do have break in periods, but they aren't like the old days... bearings seat faster, and engines don't create metal filings and sludge like they used to... a big reason why they last longer. I recommend you look at the Amsoil site
They has a lot of good advice and answers to common questions. The short quick answer is yes, use synthetic. Cheapest upgrade you will ever give your motor.
BTW.... Nice to see you Alan... hope all is well. ;)
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