Synthetic oils

[Cdndewey]

I have a Hyundai Seasall diesel engine in my boat. I am wondering what the consensus is on using synthetic oils in a diesel engine.

I'm sure there are threads pertaining to my query and I will be searching the forum and contacting the manufacturer. I am asking to see if there's any new responses.

Thanks in advance for any replies.

[ranger58sb]

Usually best to use what the diesel engine manufacturer specifies.

Some of the advertised advantages of synthetic oils... aren't always worth the extra cost. Or take more work to manage. For example "longer life" can maybe be a good thing but is best augmented by oil sampling/testing... so you know when end of life really happens. Cost of testing adds to initial cost of synthetic. Et cetera.

In any case, Hyundai probably makes a recommendation.

-Chris

[tkeithlu]

Lubricating engine oils are divided into S (spark ignition, gasoline engines) and C (compression ignition, diesels). Current diesel lube oil is API-CK, up from API-CA thirty years ago. CK covers all the Cs before it. If you stay with CK, you're covered (Hyundai may specifiy a minimum), and free to shop by price. Being synthetic doesn't help, given a set rating.

For a long time there were no multigrade diesel oils. 10W-40 is as fluid as a 10 weight at a low test temperature and as viscous as a 40 weight at a high test temperature. If you have nasty cold weather in which to start your engine, consider a multigrade.

[dannc]

I have been using a variety of synthetic oils in my truck, tractor and lawn mower engines for years for a variety of reasons.

To major reasons I use synthetic,

1. To run extended miles/hours on the oil. I test the oil each oil change, and even after going three times the recommended miles on the oil, I am throwing away "good" oil at the oil change.
2. The other reason is cold weather start up. The engines started much easier in cold weather. I used to use an oil heater to start the truck which pulls quite a bit of power for 3-4 hours that is needed to warm the engine. That power usage pays for a good bit of the extra cost of the synthetic oil.

Unless one is going to have one or both of the above use cases, I don't think it is worth the extra money to use synthetic oil.

Later,
Dan