Synthetic Oil question

Nope, the new semi-synthetic oils are good for a year, but it is a year. Don't push it.

Your engines will put pollutents and nasties into your oils and lubes.

Change your oil . Always.

Edit to Add

I have a Lawyer client whose name ends with ....bergstein. His oil is magical. No, really, never needs changing.

2 new long-blocks on order.

This comes up a lot and I'm with you, Eric. My answer to any "is it ok, should I" question is what does the owner's manual on that engine say, or what does the manufacturer say.

I'd ask this too. What have you been using? Why are you making a change?

My Man engines use Mobil 1 Delvac 5-40w. Except the first oil change good for 400 hrs. Expensive oil at $40 gal. Be sure to use synthetic that is made for diesels.

I don't think you will gain anything by going to Synthetic and changing your oil every 50-60 hours is overkill 1 year or 100 hours is a good number. MAN's use synthetic as Cskip has posted. MAN recommends 1 year or 400 hours change interval on them, on pre-common rail Man's they recommended 1 year or 200 hours with traditional oil.

At a 50 hour change interval I wouldn't switch to Synthetic. You're looking at over double the price in oil. What oil temps do the motors run at? Does it show on the display. That's the only advantage I've seen of synthetic is it will usually run at a lower oil temp. Synthetic does have a tendancy to make older seals leak that haven't leaked before.

I use delvac 1640, expensive stuff, but recommended by Man for my 820's. I change every 100-125hours which is just about every October for me, always with new filters.

Another thing to consider is that once you are using Synthetic oil, you have to stay with Synthetic oil. An oil sales guy told me that so, take it for what it's worth !

That mindset has changed over the last 5-10 years. The old mindset is that you cannot mix conventional and synthetic and once switched to synthetic that you shouldn't go back. Now either the cat is out of the bag (remember Mobil 1 used to have the synthetic oil market locked down solid for 15 years) or they have figured out there is no harm in switching back and forth or mixing the 2. You see a lot of car manufacturers using "semi-synthetic" which is conventional oil with some (the amount nobody knows) synthetic oil mixed in. Some motors the manufacturers state you MUST use only synthetic such as the Man Common rails (corvettes were the same way and that was due to oil temperature). The synthetics do tend to run a cooler oil temperature than conventional oil, and pour better at very low temperatures. They do tend to favor longer drain intervals. Such as Man common rails are rated to go 400 hours before changing the oil, the pre-common rails (same engine internally for the most part) they rated to go 200 hours. However synthetic also does have a tendancy to make seals leak on older motors that never leaked before and the price is about double for the Mobil delvac synthetic over conventional. Ring wear seems to be the cause of most marine rebuilds and I think that is oil related, but many times the bearings are in good condition and not changed during a marine diesel rebuild. Honestly, I've seen no excessive wear by using standard motor oil and changing it and the prescribed intervals in motors that synthetic is not required by the manufacturer. I generally almost always use the manufacturers oil in yachts and vehicles and feel you cannot go wrong with the oil they have blended for their engines and find the price is not really much more than going with some other brand.