Can I use a synthetic oil (Mobile)

[Ralph vaughn]

I have a 2008 sea ray 290 with merc 5.0 MPI Dual Core engines, that I just purchased. I’m changing the oil this week. Do I need to use Quicksilver synthetic or can I use Mobile 20-40W from Walmart or Napa. Where can I get the oil filter and how do I identify the oil filter to my Napa Technician.

Ralph

 

[Stee6043]

If your engine calls for the Quicksilver, I'd use the Quicksilver. It's pretty well accepted around here as a quality oil. Price isn't so bad either.

It's all I've ever used for my boats...

 

[Stee6043]

Also - the most competitive prices I generally find Quicklsilver 25-40 is West Marine, of all places...

 

[paulswagelock]

A few things. Mobil 1 does not make a 20w40, and neither does Merc. Mobil1 has a 20w50 that would work just fine, and the OEM Merc oil would be a 25w40 in either standard or synthetic blend. Both of these are contracted oils by Mercury, they do not own their own refinery or blending facility.
So, which is best, they are all fine. Honestly, Delo or Delvac or Rotella 15w40 which are all widely available and inexpensive are just as good as well.
You could pick any of the ones listed, and change it regularly, and your oil selection will never be the reason for an engine failure. They are all easily sufficient for your engine service.
If it were me, Rotella T5 15w40 from Wallyworld for $16 a gallon would go in there. Top notch, easy to find, inexpensive.
For filters, get the OEM part number and Napa can cross it to a Napa gold or silver, both would be great choices. I believe the part number is 866340k01 which crosses to Napa 7099, but verify that, going off memory.

 

[sbw1]

I find it interesting that so many people wonder about what oil to use when engine manufacturers clearly specify what oils work best in their engines. You will never be let down by following the recommendation in your owner manual, even if you end up spending an extra $14.

 

[paulswagelock]

Here is the thing though, his manual is 12 years old, the oil spec’d in it is no longer even available, and oil technology has changed significantly since then. So the challenge is to find a suitable alternative. I have tested the OEM oil, it is nothing special, but as you state will work just fine. So will dozens of other choices.

 

[BillK2632]

I personally use the Quicksilver oil - a little more expensive, but it's right there on the shelf when I am at Walmart. Walmart also has other Quicksilver items like oil filters, fuel filters gear lube etc. I also like Napa, I usually get my oil filters there - I have the old block mounted filter. Just get the # off of your oil and fuel filter, Napa can cross reference them. So you should be able to find everything you need at Walmart, but if you like Napa there is nothing wrong there.

 

[DWABoat]

Good point on the oil. I have asked many times.

My 1989 5.7 runs at about 170-180 degrees. Synthetic oils were not common back in the 80’s.
So...if I start using in the old 5.7, a new Pennzoil synthetic designed for my 2019 6.4 Dodge Hemi running at 210-230 degrees, am I risking under protecting my old, colder running engine? Under a load, my previous 2013 GM 6.2L would get an oil temp of 260 degrees.

These synthetics don’t even hit their peak lubrication until the mid-200 temperatures. My old 5.7 coolant wont even get to 195.

I have been told to use the synthetic blend currently recommended but not pure synthetic.

Any thoughts?

 

[sbw1]

The main advantage of synthetic is the uniformity of the product. It is slicker because it has smaller molecules and is free of impurities such as the waxes found in dyno oil. This allows drivers to extend the oil change intervals out from traditional levels and achieve better performance with cold starts. However, most boaters change their oil every year instead of by hours of usage. Going to synthetic on the basis of less wear on start up and extended intervals is a bogus argument since traditional oils recommended by Merc or whoever built the engine work well. Many engine companies are now recommending the synthetics because the technology has changed. But if dyno oil was recommended for your engine when it was built, you will not go wrong by using a high quality oil equivalent to the original recommendation. The important thing is to use the correct viscosity and change it at the recommended interval.

 

[paulswagelock]

Synthetic oil strong points are cleaning, wider temperature bands, extended service, shear stability. In the marine environment, the overall engine temps are cool but the combustion temperatures are the same as a car engine. However, the main point of extending oil change duration is not needed for a boat, nor should you, so the premium price of a synthetic isn’t really warranted. It would work fine, but not any better for the price difference.
Edit: SBW1 beat me to the punch....

 

[Spark600]

I have two boats, On my 23' boat I have a 200 HP Honda that I use Quicksilver 30W ever year and at the end of the year I get oil sample for the motor, Never had a bad report on the oil, One year I said let me try the Sierra 30W oil and the report came back that the Viscosity of the oil was low.
I will never was an off brand of oil again.
I attached a copy of the report

 

[Ralph vaughn]

Thanks everyone. Your varied replies were super-informative and allow me to make an informed decision You guys are awesome with the experience you have and share

ralph

 

[juggernaut1]

I have two boats, On my 23' boat I have a 200 HP Honda that I use Quicksilver 30W ever year and at the end of the year I get oil sample for the motor, Never had a bad report on the oil, One year I said let me try the Sierra 30W oil and the report came back that the Viscosity of the oil was low.
I will never was an off brand of oil again.
I attached a copy of the report

To be fair, your fuel contamination might have had something to do with your lower viscosity reading in that report.

I've moved away from the Mercruiser 25/40 oil to 15/50 POA/Ester racing oil with no viscosity improvers. The differences/benefits I see is virtually no oil consumption throughout the year and the oil pressure recovers much faster after coming off the plane when compared to the Merc oil.

 

[mnm99]

On sale now. 40% off
https://www.marinepartssource.com/s...etic-blend-marine-engine-oil-sierra-18-9440-4

 

[BLmicro]

You have to watch the oil weight if your motor has needle bearings (i.e. roller lifters or rockers), don't want anything too thick otherwise those bearings get starved in cold starts or long idle periods. You need to stick to the OEM weight recommendation religiously in those case. 100% synthetic is always the best bet unless you are in a break in period. Race oils are the best since they have higher zinc but that doesn't work well with catalytic converters but that's not a boat worry. Mobile 1 or Rotella would be top choice. For a non-roller motor, 10-30W is standard unless you are in extreme temps or the motor has issues.

-BL