what oil to use?

[BarryK]

Is anyone using the Quicksilver 25W40? I have only owned the boat for a couple of months and need to do my first oil change: 1990 Crusader 454s. The mechanic said to use the Quicksilver but the Rotella is cheaper and available at Walmart!

The old service manual says straight SAE 40 above 50 deg. "The use of multi-viscosity oils is not recommended"?? That was written in about 1992 for engines 1980 -1992.

Thanks,
Barry

[Cooler]

Barry - lot of forum members have high regard for Rotella, but I notice most of them being diesel applications. I would check to see what the previous owner was using. I work part time at a marine store, and we sell a heck of a lot of Quicksilver 25W40. I use it and have never had issues. Mercruiser requires Quicksilver while engines are in warranty. This is one place to not worry about a few bucks. Considering number of hours you run engines, it is really pennies. That first number only pertains to temperature the oil can flow easily. I doubt you are starting your engines in 25F temps. Straight weight would be fine. Maybe Viper will chime in. He is the resident expert! My Crusader manual says to " Disregard any reference to multi-viscosity oil printed on engine. Such references is intended for automotive use only, not marine application. " er

[Cliffm]

I have used Quicksilver, but gone back to Dello400 15w-40 (the diesel truck blend) I get it at Costco (3) 1 Gallon jugs cover both of our Volvo 8.1Gi's.

I wouldn't hesitate to use Rotella via Walmart.

[Tireless]

Used Rotella for years as stated before, both Gas and Diesels. Yes you will pay more for brand named stuff, but I am not sure if it is really any better. This comes from mechanics and other boat owners that have bee using this stuff for years. You have to use what you are comfortable with based on what your have experienced or heard from others in the know.

[BarryK]

Thanks everyone!

[Cooler]

Yea, this is one of those areas where most oil is similar as long as you use a proven, quality brand. I just like to use the same type every year. Only significant difference would be if a skipper was a high HP, full throttle all the time type. You know, the rumblers you can hear 5 miles away. er

[bud37]

Any time you are having doubts that your oil choices may be wrong....consider this.

What do truckers and fleets use in their highway trucks. Some of these truck engines have turbos with upwards of 2000 Ft pounds of torque, and between 15 to over 20:1 compression. They may be pulling up to 120,000 lbs down the road in hot, cold, rain, snow , you name it. They run all day long and will go for up to a million before an in frame rebuild.

I have considered the 25w40 as well, good oil , nobody seems to know who makes it for them though.... But I have used rotella and delo 15w40 in everything without a cat. converter.

[tomschauer]

https://www.api.org/products-and-servic ... b-gasoline

What ever oil you use, make sure it meets the API specs for your engine. Oil with only a "C (compression)" spec should not be used on gasoline engines. Oil with only an "S (spark)" rating should not be used on diesel engines. Most combo D and S rated oil should not be used on any catalyst engine.

[tomschauer]

I found something kind of interesting. After my last post, I pulled some oil off my shelf. I have some mercury quicksilver 25/50 synthetic blend. It has no API rating but has a NMMA rating of FC-W four stroke catalyst compatible. This oil is on the approved or tested, (not sure which is the proper definition) NMMA list. I also have some Volvo Penta full synthetic gasoline engine oil. This is the " factory required" oil for my 2018 Regal with the Volvo 4.3 240 hp engine. This oil has no API or NMMA rating and I don't see it on the NMMA list?

http://www.nmma.org/certification/oil/fc-wcat

[Viper]

Here’s my two cents, and this is based on recent discussions with people in the know with respect to all things oil; chemistry, marketing, economics, politics, etc. I’m not the expert but will pass on what I’ve learned lately that has forced me to rethink my view of what oil to use in marine applications. Now there will be those that disagree with the following and are set on continuing to do what they’ve done for years in spite of what anyone says, and if it works for them and they’re comfortable with it then so be it.

Without getting into a bunch of technical jargon about the chemistry involved, I’ll start off by saying that I think we can all agree not all oils are created equal. What some may be sceptical about is whether there is a definite difference between automotive and marine formulations. I’ll start off by saying that the standard for the average automotive oil is lower than the standard for the typical marine oil which has a more aggressive standard for a few reasons. Usually the only time automotive oils approach this higher standard is in their high performance formulations, but they will still lack the additives needed for the marine environment. The standard automotive oil will meet standards for typical driving conditions well enough to at least ensure it gets the manufacturer through the warranty period. That is not to say you can’t get a few hundred thousand miles from these oils but that is in a well maintained automotive application which doesn’t experience the types of loads that marine engines do unless you’re talking racing, but in that environment, you won’t get near that longevity either.

A big enemy of oil in a marine application is water. Oil attracts moisture, and because boats don’t get driven every day like their automotive counterparts, in fact they might sit for weeks or months, marine oils tend to have a more aggressive emulsifier package to help keep the oil in suspension until the next run cycle heats the oil enough to drive out the moisture. Anti-corrosion package levels are also considered to combat the higher levels of moisture. If you insist on using an automotive oil in your marine engine, don’t leave it in the crankcase for weeks on end or over a long/winter layup, the moisture package isn’t good enough.

Piston skirt issues are common in marine applications because of the constant higher loads and boating habits. To help prevent that, marine oils utilize extreme pressure additives and a more aggressive pour dispersant and viscosity enhancer spec. This helps widen the window of operating conditions especially in the much hotter marine combustion chamber considering an oil’s primary purpose is to remove heat.
While I’ve used mostly OEM branded marine oils, I would on occasion use oils such as Rotella -T, even in gasoline applications as many others do. It’s a good oil but it’s a diesel oil with higher levels of zinc which is great for diesel engines but not for gasoline engines in those densities. While some zinc is desirable as it makes up part of the extreme pressure additive mentioned above, higher levels then that present in good marine blends can lead to pre-ignition and damage a gasoline engine.

Combine the above and an NMEA standard and certification in most cases (which costs money) and you soon start to appreciate the difference in both the oil’s performance and its price point. You may find a high performance automotive oil close to the same spec but it probably won’t be that much cheaper.
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As for what I’d use; Merc oil 25W-40 for older applications and full synthetic for newer engines. Merc would now prefer that only synthetic oils be used in all their engines. There are some valid reasons for it but that’s another thread. Same for Volvo; conventional for older engines and synthetic for newer, especially if it’s a Volvo 8.1. While the base oils are basically the same and likely from the same petroleum company, probably Mobil or Amsoil, the two manufactures have some differences to consider in their engine builds that require specific attention to their blends. As for Volvo diesels, I’m sticking with Volvo oil. Can you use other less expensive oils? Of course you can, but you can do so much better for the most expensive piece of hardware on board. I always say skimp on the less important things, oil isn’t one of them, it’s pretty important..…IMO