Rotella T4 15w 40

[Cliffm]

I use Delo 400 SDE 15W-40w available at Costco (Wa) for $36 USD 3x1gal jugs which does "both" out 8.1L Gas motors.
I also have been running this for years in my 1967 Mustang due to "flat" tappet performance camshaft design.
No issues in either, also running WIX/Napa Gold oil filters in all my vehicles/engines & Generators.

[Viper]

We're talking about conventional oil right, not synthetic? If you want to stock up or do an oil change only once a year, then synthetic is the way you should be going. It's still crude oil but way more refined and much more stable which allows for longer storage and change intervals.

Marine engine OEMs know most boaters will only change their oil once a year and is one of the reasons they are all moving to synthetic recommendations now. For some reason when it comes to their cars, changing conventional oil every 3 months whether they use the vehicle often or not is an acceptable practice but tell the same person to do that very same interval with their boat and they think you're nuts. Volvo caught on to this years ago and because they wanted to maintain their reputation on engine longevity, they recommended synthetic long before any of the other big players did. Merc finally caught on just a few years ago after taking a look at some failure rates, other data, and feedback from the field. They're all the same blocks though before and after synthetics. One of the main considerations was the oil's longevity.

[Midnightsun]

There is no more 3 months on cars that I know of. Basically the change oil light/indicator comes on when it is due. Bottom line, temp, heat/cold and a bunch of other stuff with an algorithm slapped on and it tells you when. There may also be a time limit but not that I know of. My Mercedes is unreal, get about 20,000 km before I need to change it and this is an AMG which is not exactly pampered. 20,000 km takes me almost a year by the way.

I am way too cheap to put in 12g of synthetic every year mainly because the boat is not really used all that much and 95% of this is at 1250 rpm which barely gets it up to operating temp. Maybe 10hrs a year at 3100 rpm on plane and that would be conservative. This year I probably did only 5 hrs on plane.

[tomschauer]

"Why did you decide on the 15w50 ?....just curious about the grade difference, not the cost."

If you x ref the merc oil on the Mobil site, they recommend the 15/50.

[RGrew176]

This could explain why my mechanic prefers to change the oil in his customers boats in the spring vs the fall. I may have to rethink my process.

[Cliffm]

QR_BBPOST This could explain why my mechanic prefers to change the oil in his customers boats in the spring vs the fall. I may have to rethink my process.

I'm with you, I'll be changing in spring, prior to the "more use months".

[km1125]

QR_BBPOST

QR_BBPOST This could explain why my mechanic prefers to change the oil in his customers boats in the spring vs the fall. I may have to rethink my process.

I'm with you, I'll be changing in spring, prior to the "more use months".

The whole concept of changing in the fall vs the spring is so that you don't have contaminated oil sitting in the bearings all winter long. It's a bit acidic and will cause pitting in the bearing surfaces.
However, much of that thought was developed during the carb engine years, where you got a significant amount of fuel contamination into the oil. I wonder how much of an issue it is nowadays with injected engines. Could still be, I just don't know. If it's not, then there's really not a reason to change every spring either unless you've accumulated quite a bit of hours on the engine.

[Midnightsun]

See here. https://boatplanet.com/the-captains-blo ... ng-or-fall

[Viper]

QR_BBPOST ....much of that thought was developed during the carb engine years, where you got a significant amount of fuel contamination into the oil. I wonder how much of an issue it is nowadays with injected engines. Could still be, I just don't know. If it's not, then there's really not a reason to change every spring either unless you've accumulated quite a bit of hours on the engine.

The contamination is a result of the byproducts from the combustion process regardless of carbed or injected. Some of the byproducts are corrosive so you don't want some internal engine component surfaces sitting in that soup for very long, especially in a static state such as during winter layup. The damage doesn't happen in one winter but is accumulative and may become a problem over time.

The main thought of those that swear Spring oil changes is the way to go is based on the concern that changing oil in the Fall means you're starting off the Spring with 6 month old oil. I'd be more worried about the corrosive soup though. The other Fall oil change concern was condensation in the sump over the winter adding water to the fresh oil. Marine oils however have a much better additive package than automotive oils to deal with water, and once you run your engine to temp on a good run in the Spring, it's likely you'll dissipate that water in a reasonable amount of time. Having said that, the official word from CAT is to replace the oil in the Spring because of the condensation concern, however theirs is not a marine oil, it's an automotive blend without the same additive package designed to deal with higher water levels. In their world and many other diesel OEMs, their equipment is predominantly in transports that are running more than they're at rest, so it's not typical to have to deal with any real levels of moisture in the oil.

[pepmyster]

I've always changed my oils in the fall. The same thinking as many to not have contaminated oil sitting in the block for the fall lay up. Our company changed the oil change schedule for our cars from 6 to 8000km, or, 6 months. There are others now that change the filter only every other time. Which, I don't ever want to do. Hans, you are right, once a year for the Mercedes. Mine never sees the rain or snow, Once a year means around 3000 km, regardless .