Ignis Fatuus
New member
Can I use engine oil (10w 40) that I use for my car in my outboard engine. The specification is correct but is there something special about outboard engine oil over car engine oil?
What 4 stroke engine oil
- Thread starter Ignis Fatuus
- Start date
VicS
Well-known member
Provided you use a good quality automotive engine oil of the correct viscosity grade and appropriate API service specification, yes, you can
I am surprised that your owners manual does not say so, specifying the viscosity grade the acceptable API specifications
Most likely to be SAE 10W-30 and API SG, SH or SJ
Laysula
Well-known member
Marine engine oil is exactly the same but 3 times the price,
I just used what I had left when I changed the oil on the car..
I just used what I had left when I changed the oil on the car..rszemeti
Active member
I would even go as far as to say that provided you have roughly the right grade of oil, you are fine.
Remember that most cars get 1 oil change a year and will do (roughly) 400 hours (8 hours a week) of use a year, covering perhaps 15,000 miles.
A typical yacht seldom seems to put 100 hours a year on the engine, often considerably less, yet still (hopefully!) gets the full oil and filter change ... even with a not-so-great oil, it is probably getting a much easier time than your avergae car.
Remember that most cars get 1 oil change a year and will do (roughly) 400 hours (8 hours a week) of use a year, covering perhaps 15,000 miles.
A typical yacht seldom seems to put 100 hours a year on the engine, often considerably less, yet still (hopefully!) gets the full oil and filter change ... even with a not-so-great oil, it is probably getting a much easier time than your avergae car.
RichardS
N/A
rszemeti
Active member
I suspect many outboards on tenders put in less than 10 hours a year.
Still a good idea to change the oil at the end of the season, from a water content perpective if nothing else.
Still a good idea to change the oil at the end of the season, from a water content perpective if nothing else.
steve66
Well-known member
Yes usually 10/30 or 10/40. Genuine honda oil had 24 carat gold in it ( well for the price I think it has).
I have seen 25/40 on occasions. As long as it's decent oil it will be fine
QBhoy
Well-known member
In all honesty, in a low tech engineime this, you would be fine using car oil of a similar grade...but...marine oil is not the same as oil used in cars. Marine oil has moisture protection in it and is designed for such an environment. I always tend to use either OEM recommended oil after searching for it at its cheapest online or you will usually find the excellent Rock Oil brand has it covered at a fraction of the price and meets the spec too.
VicS
Well-known member
Marine engine oil is exactly the same but 3 times the price,
Oils for marine four strokes which are certified to comply with the FC-W standard have been developed to take into account differences in two key areas:
Firstly prolonged operation at high rpm and high temperatures. Something that rarely occurs in automobile applications.
Secondly increased corrosion resistance reflecting their use in humid and often salty conditions.
thinwater
Well-known member
^^ This. I've worked with guys on the committee that develops the spec. In fact, some PCMO will pass the test, but simply have not gone to the expense of testing. But you won't know. Buy FC-W is simpler and safer.
Ignis Fatuus
New member
I can't help but be a little sceptical about Marine Oil. I've just checked out FC-W on the internet and found it to be a certification that has been developed by an organisation called the National Marine Manufacturers Association. It looks to be American. Is this not just a ploy to sell oil to mariners at inflated prices? After all, the bottom half of the four stroke engine is a sealed unit and so not open to the salty environment. It is adequately cooled with a plentiful supply of cold sea water. I don't know what the maximum revs are but I'd be surprised if they are more than my motor bike which red-lines at 14000.
thinwater
Well-known member
No, it's not. I'm not in the industry, but I am familiar with the work that went into development.
Passenger cars do not get seawater (it only take a few PPM to make HUGE difference in bearing corrosion rates--you can Google this) in the lube (leaks), sit unused for weeks at a time and sometimes a year at a time, and a bike engine does NOT operate at full load for more than seconds, even in racing conditions, whereas it is normal for a marine engine to operate at WOT for hours.
There is also no reason non-marine manufacturers cannot meet the spec. Many do.
Yes, NMMA is American. I think you will find that most petroleum specs and antifreeze specs originate in the US, because we're into oil. For example, the British engine coolant committee shut down ~ 15 years ago and merged with the US group (ASTM D15, of which I am a member). The group works on US AND international standards.
Hot Property
Well-known member
Maybe on your side of the pond but not this side. Fuel costs are significantly higher and fellow boaters I personally know range from a 16 ft Fletcher with 50 hp to a Fairline GT 48 with 900 hp. None run at WOT for more than a few minutes, only to clear the cobwebs out.
I run my verado at around 4,000 RPMwhereas the WOT is 6,400. Most petrol cars cruise at 3-4000 rpm so apart from an increased risk of salt I can't see much difference. I do around 75 hours a year, change the oil and filters and go for a run at least every 3 weeks even in winter to heat the oil to around 100 degrees Celsius to drive off any moisture.
VicS
Well-known member
Nothing new.. NMMA is already familiar to us as the organisation responsible for the TC-W specifications of oil for 2 stoke outboards.
thinwater
Well-known member
Many outboard-powered cats run at 70% for 10 hours at a time and consider it normal. Some work boats with high load factors do the same. Running out to the Canyon (Gulf Stream) from east coast ports it is normal to run at 70% for 2 hours each way, 2x per day.
The point is, that is what the spec is designed for. Really. If you are not doing that, then that portion of the spec many not apply to you. But the spec assumes 70% for long, continuous periods, which is far different from PCMO, which is based on a few bursts, but mostly 10% load at 2-3000 rpm.
And don't underestimate salt. The condemning limits in lubes and coolants is typically 10-20 ppm. Only 1 part per 2000 seawater, including water that has boiled out.
The point is, that is what the spec is designed for. Really. If you are not doing that, then that portion of the spec many not apply to you. But the spec assumes 70% for long, continuous periods, which is far different from PCMO, which is based on a few bursts, but mostly 10% load at 2-3000 rpm.
And don't underestimate salt. The condemning limits in lubes and coolants is typically 10-20 ppm. Only 1 part per 2000 seawater, including water that has boiled out.
Last edited:
Laysula
Well-known member
I stand corrected. Thank you.
Other threads that may be of interest
