Synthetic oil 🛢

When I had my DF40 (2019 suzuki), I asked about this. Mike at Maple Marine told me that most marine/outboard OEM 4-stroke oil is specified as a synthetic blend and not straight synthetic. I don't know the reason, but this tracks with what I've heard elsewhere.
 
One caution - just watch out for running oil that is too light weight. Boats run under extremely high continuous load and subjects the oil to shear. In our ski boat with a 350 V8 I always run 15w40 Rotella (conventional oil) which generally designed for diesels. Light weight oil can shear and cause your oil pressure to drop, and cause premature wear. As always - check your owner's manual.
 
scott craven said:
Is anybody running synthetic oil in their 4 stroke outboards with good results?
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I was told, and I tracks from my experience, that full synthetic increases oil consumption on engines with horizontal piston travel due to its improved ability to resist being scraped off the cylinder wall by the oil control ring(s). This could cause problems downstream in catalyst after treatment components, although I suspect it’s not a serious concern. What may be a more realistic concern is Synthetics’ hydrophobic properties. When used in a marine environment where water may enter the lubricant, it’s resistance to stratification with water could result in free water being pumped into areas requiring good lubrication.

Having said that, full synthetic is superior to semi-synthetic lubricant is every measurable way, including resistance to shearing and extreme pressure, oxidation, viscosity breakdown, etc. It generally has double the Viscosity Index of an equivalent conventional oil, and does so without the addition of VI improvers (additives) that break down over time.

I run synthetic in every company asset, personal vehicles, except my outboards and the cabin Land Rover.

Edit: The Cabin Land Rover runs on Love
 
I think it drains too much when sitting. So the start up is a little drier.

Ya, the rotella is very good. Decades ago they tested it in a trucking company vs full synthetic at the same mileages. No difference if anything maybe a little better.
 
Tried it with a brand new 175 zuke in 2006. Ams oil full synthetic right from new. Started using oil before 3 year/1000hr warranty was up. Had it into CR Suzuki just before warranty ran up. They tore apart and found all the rings were stuck. Zuke didn’t go good for the warranty so I had to pay for rings/bearings and labour since it was already apart. Ever since I’ve run conventional rotella 15-40 with all the vitamins and minerals, same as I run in my duramax. Never had an issue since 2009, I put a fair amount of hrs on every summer. Rotella is cheap, change every 100hrs. I have used that semi synthetic ecstar when it’s on sale and it has been good also. No fancy synthetic for me anymore.
 
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Doubleheader said:
Tried it with a brand new 175 zuke in 2006. And oil full synthetic right from new. Started using oil before 3 year/1000hr warranty was up. Had it into CR Suzuki just before warranty ran up. They tore apart and found all the rings were stuck. Zuke didn’t go good for the warranty so I had to pay for rings/bearings and labour since it was already apart. Ever since I’ve run conventional rotella 15-40 with all the vitamins and minerals, same as I run in my duramax. Never had an issue since 2009, I put a fair amount of hrs on every summer. Rotella is cheap, change every 100hrs. I have used that semi synthetic ecstar when it’s on sale and it has been good also. No fancy synthetic for me anymore.
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VGG?
 
Phone was listening to me as usual and this video popped up regarding using diesel oil in a gas engine.


There’s also the old debate of Marine oil vs vehicle oil. As far as I can tell the marine oil has more additives to combat moisture in marine environments. The only time I’ve ever had moisture intrusion is from a blown head gasket.
 
Doubleheader said:
There’s also the old debate of Marine oil vs vehicle oil. As far as I can tell the marine oil has more additives to combat moisture in marine environments. The only time I’ve ever had moisture intrusion is from a blown head gasket.
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There was a study done in a previous post analyzing marine oil and automotive oil.
At the end of it while some oils were better than others, there was no significant difference between marine and automotive rated product.
 
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