I hate to ask - which oil?

Joined
May 24, 2021
Messages
1
OK - asking about opinions on oils is scary, LOL! Here's a related topic.

1997 Cruisers Yacht 3575 with twin Crusader 7.4L 454XL gasoline engines (fuel injected). Engine hours about 650 each. I run in Lake Michigan, so I'm only in the water from SPring to Fall - run about 50 hours per season.

The prior owner had no idea what kind of oil was put into these engines since the mechanics at his storage facility always did his oil changes. I was unable to reach the mechanics, at first. The cover on the engines said SAE 40. When asked it seemed like most people were leaning toward Rotella T4 15W-40, which I purchased.

Today, however, I spoke to the mechanics at the facility, and they told me they only use Quicksilver 25W-40. I don't mind spending a little more money for the Quicksilver brand, but here's the question. Is there a disadvantage to CHANGING oil types, or is there an advantage to NOT CHANGING oil types? My best assumption is that if it ain't broke, don't fix it - so stick with what has been working - Quicksilver.

Then again, I hear that Quicksilver has reduced pH and Zn in their formulas so maybe Rotella is a better choice?

Thoughts?
 
I personally wouldn't hesitate to run the T4 for a season (50 hrs). Change back to the quicksilver after that if you like.

If they were my engines, I would likely be running 15w50 Mobil 1, or 20w50 Valvoline VR1.

Sounds like a nice yacht. Enjoy it this summer!
 
25W40 marine type oil is marginally better for your application as it will tend to stay in grade longer with the high RPM, high oil sump temperature conditions most marine engines run under, as it is formulated from heaver base stocks with little or no viscosity modifiers that can shear down. The additive packages in marine oil are also engineered to address the different problems that marine engines have in general vs automobiles... moisture, corrosion, long change intervals, fuel dilution (leaky carbs), lots of wide open throttle operation, long periods of inactivity, etc.

Personally, I would be fine with using the T4 until the next oil change, but I would normally use marine grade oil if given the choice.
 
I second the M1 15-50. can be had at wallyworld for ~24 bucks a jug. As others have said a marine engine UNLIKE a car the engine is under heavy load all the time ...there is no coasting. there's no reason not to use full synthetic.
 
I would go with either the Rotella T4 15W40 or the Quicksilver 25W50. Both are high quality oil.

Most pleasure boat engines die of water ingestion, not worn out.
 
You'd be hard pressed to find a modern SAE 40 that wouldn't pass 25W. SAE 40 covers quite a range and you get some HTHS with your KV100C.

We established on another thread that the FC-W is 18 years old, 2003-04, or about a SJ-SN quality engine oil.
 
I wouldn't run a 15/40. As someone else posted marine engine oil runs hot. A 15/40 is too light and will shear. No matter what you "hear" 15/40 is not a better choice.

Engine calls for a straight 40 and any 25/40 is just about "there".
Another choice would be 15/50 or 20/50 with a bias for the 20/50

Personally, will leaving the 15/40 oil in for the season matter, I guess not, me? I would change it out though. Im against that choice and would go as far to say, after a few good long hard runs you maybe able to tell the difference by the amount of valve chatter once the oil temperature gets hot. Thats just me, you may not have that happen but I have seen it first hand in some cases. Its just not the best choice but your not going to blow up your engine over it.
 
When I worked at a marina some 20 years ago they used regular 10w-40 oil. Marine specific oils contain more rust inhibitors than regular car oil.
 
Back
Top