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Old 27-08-2009, 13:46   #1
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Synthetic Oil Change Frequency

I just switched engine oil to synthetic for my Volvo MD2030Bs. Although my manual suggests changing oil every 100 hrs, I believe I should be able to extend the interval much longer with synthetic.

Does anyone have any advice on extended oil change interval for marine diesels? Also, if I use extended interval should I still change the filter every 100 hrs?

For cars, the synthetic oil change interval is every 25,000 miles or 1 yr which ever comes first and 15,000 miles under severe conditions. If I extrapolate the numbers conservatively, I should get 500 hrs between oil changes. Obviously, marine diesels work much harder than road vehicles, but even a 200 hr interval would be twice as nice as regular oil.

My rationale for switching to synthetic oil is too reduce oil changes, reduce disposal problem while cruising, provide better lubrication to engines and to eliminate an oil change when the boat is idle during hurricane season (synthetic doesn't breakdown as quickly). OBTW, synthetic oil price is about double that of petroleum oil. If I extend the oil change interval to 200 hours, extra cost is a wash and my labor is cut in half.
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Old 28-08-2009, 16:37   #2
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300 hours

An "oil engineer" advised me to change oil and filter every 300 hours or whenever the oil level begins to drop, which ever occurs first. You can use a finer oil filter with most sythetics, if desired.
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Old 28-08-2009, 18:09   #3
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An "oil engineer" advised me to change oil and filter every 300 hours or whenever the oil level begins to drop, which ever occurs first. You can use a finer oil filter with most sythetics, if desired.
Thanks, Rick. Getting 300hrs between oil changes makes synthetic oil a money saver as well as a time and mess saver. It also precludes hauling lots of extra new oil around while cruising and hauling the dirty oil back to the US for disposal.
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Old 28-08-2009, 18:34   #4
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I don't think anyone can put an absolute hour number to the change frequency if you want to extend your change interval. This is due to significant differences between engines. The way to be sure is to get your oil tested. Spend a few $$ at 100, 200, 300, 400 hours to see how your engine wears its oil. For example:
http://www.testoil.com/pdf/standardreport.pdf
Yes, synthetic oil takes longer to break down and suspends contaminants better, but at some point even synthetic oil will become overly contaminated.

Once you've established the point at which your oil becomes unserviceable, you know when it is safe to change. I would change the filter at the manufacturer's recommended interval. Contaminants must be removed regardless if the oil remains stable.

Brett
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Old 28-08-2009, 19:18   #5
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LtBrett, Great suggestions.

I see your point. A worn engine would put more contaminants in the oil and require more frequent oil changes than a healthier engine. I found an oil test company for non-commercial customers and they want $99 per test. Does that sound like the going rate?

Also, changing the filter at required interval sounds like cheap insurance and is easy to do. I'll follow that advice.
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Old 28-08-2009, 20:33   #6
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I am leery of long life oils.....not because there is a problem with them...but rather to the mindset that people get from being afraid of looking in their engine compartment.

I don't know what causes this malady....but your engine should be "eyeballed" daily.

As a paid engineer on tugboats and three yachts.....My rule was, if you are on watch, YOU will poke your head into the engine compartment every hour or so.
Listen-Look-Smell put it in the log.......If you notice anything unusual...wake me up.....I will NEVER BE ANGRY.......
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Old 28-08-2009, 20:52   #7
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Sounds like you are looking at Amsoil. I have over 15 yrs experience with the synthetic. Right now it is in my Cummins/Dodge, my Jeep, my wife's Mercedes, and my Yanmar. I believe it is the best.

My first experience with it was a 1981 Mercedes 300D. The vehicle used one quart every 800 miles of regular oil. I switched to Amsoil and used zero oil every 6000 miles (change time for me). I do not use the extended intervals as they suggest, but instead change every 5000-7500 miles. On the boat I change it every 75 hours regardless of the situation. If you want the extended intervals, you will need oil testing. My opinion is, you can simply change the oil for a few dollars more and not second guess yourself.
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Old 28-08-2009, 22:08   #8
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Gasoline vs Diesel

I am not real sure about extending the oil change intervals with synthetic oils in a diesel. May be OK, but. The carbon particles in diesel seem like they will load up the oil. This is why the oil in a diesel turns black isn't it. Or am I missing something entirely.??
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Old 29-08-2009, 03:22   #9
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From AMSOIL site. I would go a bit over but think the best objective would be to keep the engine tip top. I use synthetic in all my cars but really do not extend changes much, just wanting to keep engines clean and running forever. I do not sweat the oil change light but change it soon after it comes on, on my cars it allows a 3 week window for changing without concern.

SERVICE LIFE
AMSOIL Synthetic Heavy Duty Diesel Oil is recommended for extended drain intervals in unmodified(1), mechanically sound(2) vehicles or equipment as follows:

Diesel Engine Service

• Normal Service — Up to 25,000 miles or one year, whichever comes first, or longer based on oil analysis.
• Severe Service — Up to 15,000 miles or one year, whichever comes first, or longer based on oil analysis.


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Old 29-08-2009, 06:00   #10
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Originally Posted by Nice N Easy View Post
I am not real sure about extending the oil change intervals with synthetic oils in a diesel. May be OK, but. The carbon particles in diesel seem like they will load up the oil. This is why the oil in a diesel turns black isn't it. Or am I missing something entirely.??
Not to mention the acids. I don't recall ever seeing a claim that synthetics neutralize the acids any better than conventional oils, though maybe one is out there? Synthetics really can't do much to prevent contamination from the usual diesel culprits.

If using a good quality diesel oil like Shell Rotella you should not need to worry about anything and if changed regularly you're engine will run a good long time.

In my cars I have seen no benefit to synthetics and only detrimental stuff like pesky oil leaks. My M3 runs the suggested synthetic oil and this car has had TONS more oil leaks in 120k miles, of course it's NO Japanese car in terms of reliability either, than my wife's Honda Pilot at 135k. Both engines are clean inside and run well. I have run vehicles to over 200k with zero engine problems related to engine oil and always run conventional oil, except in cars that came from the factory that way like the M3..

This was the top end of my Westerbeke 44B Four at 2878.2 engine hours, just as the valve cover came off. If I were to use a synthetic I'd not increase my change intervals by much, if any, at all.. It has only ever had Shell Rotella 15W/40. Personally I don't see much if any added benefit to synthetics in small marine aux engines and I've run commercial fishing boat engines to well over 8k hours on Rotella or Dello.. Synthetics have some great attributes but the things that kill marine diesels are usually not related to oil unless ignored or not changed on a regular interval..


2878.2 hours close up:
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Old 29-08-2009, 06:03   #11
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Marine diesels and auto diesels are engines that see two different types of uses. I wouldn't use the two to compare oil change intervals. A marine diesel for the most part is under a constant load. A car diesel has the advantage of far less loads. A car is normally used every day, a marine diesel can sit for weeks between uses. Oil not only loses it's ability to properly lubricate over time it also holds exhaust by-product that turns acidic and can react with internal components. Oil changes are a pain to be sure, even on the rare easy to get to engines. Perhaps an easier oil changing system would be a better option in my opinion than trying to extend factory recommended intervals with synthetics.
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Old 30-08-2009, 17:31   #12
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Originally Posted by CAELESTIS View Post
Sounds like you are looking at Amsoil. I have over 15 yrs experience with the synthetic. Right now it is in my Cummins/Dodge, my Jeep, my wife's Mercedes, and my Yanmar. I believe it is the best.

My first experience with it was a 1981 Mercedes 300D. The vehicle used one quart every 800 miles of regular oil. I switched to Amsoil and used zero oil every 6000 miles (change time for me). I do not use the extended intervals as they suggest, but instead change every 5000-7500 miles. On the boat I change it every 75 hours regardless of the situation. If you want the extended intervals, you will need oil testing. My opinion is, you can simply change the oil for a few dollars more and not second guess yourself.
Yes, I put Amsoil in the starboard engine and plan to change oil on port side next week. Everything I read indicates that synthetics lubricate better than petroleum oils, so even if I keep the same change schedule I'm still helping the diesels live longer.

I appreciate all the inputs on this subject. I'm not sure what I'm going to do about the change interval and whether the risks outweigh the gains. I may invest in some oil testing after 100 hrs to see what kind of shape the oil's in and go from there. Intuitively, I think the interval may be extended while actively cruising and engines are used frequently. Dirty oil that sits in the sump for long periods and gets "stirred up" once every other month probably needs the most frequent changing.

Has anyone done any testing on synthetic oil at the required change interval? Unfortunately, you can buy lots of oil for the cost of testing.
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Old 30-08-2009, 19:34   #13
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All synthetic oil is refined under licence granted by Mobile as in Mobile One. VW specifies synthetic in all its Diesels and all my cars and truck get synthetic from time of new on, with oil changes at 5k.

Boat engines are being run uphill all the time and with that in mind I will shell out or Shell in for oil changes reccomended for severe service and use synthetic. What is a little oil vs and early overhaul?
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Old 30-08-2009, 19:42   #14
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Don't forget the flash point of synthetic oil is much higher. Therefore fewer burn products are created on the cylinder walls and consequently the oil stays cleaner. I have been using synthetic oil in my cars and boats since 1978. I presently use Delvac I. Adding this to 454 MercCruisers in my Bertram completely stopped any oil loss for each season.
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Old 31-08-2009, 08:42   #15
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Don't forget the flash point of synthetic oil is much higher. Therefore fewer burn products are created on the cylinder walls and consequently the oil stays cleaner. I have been using synthetic oil in my cars and boats since 1978. I presently use Delvac I. Adding this to 454 MercCruisers in my Bertram completely stopped any oil loss for each season.
Good point. I'll watch the color of the oil to see if it gets black as quickly with synthetic as petroleum. Perhaps this is the reason change interval is much longer for road vehicles. I read a study about oil change cycles for large fleet vehicles and they change oil on a time schedule rather than based on mileage. They are more concerned about a breakdown of the oil lubrication over time rather than contamination of the oil based on miles or hours. If my memory serves me correctly, some of the fleet vehicles are regularly getting 15 to 20K miles between oil changes.
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