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Old 12-07-2011, 18:25   #1
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Synthetic Oil vs Conventional Oil

I realize this might be apples compared to oranges, but can you use synthetic oil in a marine engine?

the reason I ask is....I bought a new Ford Ranger truck back in 1996 and have used Castrol synthetic oil in it since Day 1. I can't kill it. I have beat the crap out of that truck. The odometer stopped at 185K miles about 10 years ago.....I know I've put at least that amount on it since. Still runs great....looks like hell, but what the hell. Even drove it from Orlando to Atlanta last fall....dream ride there and back. I attribute it to the synthetic oil.

Just curious if it can be used on a marine engine and if any of you Tars have used it?
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Old 12-07-2011, 18:34   #2
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I use amsoil I spent a lot if time putting my cummins in so I use an oil that is engineered fir purpose. No big deal if you disagree. I think synthetics are better.only 500 hours on my cummins. It's not that much more. In 5 oil changes I've spent a an extra 200 bucks in 4 years
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Old 12-07-2011, 18:50   #3
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Re: Synthetic Oil vs Conventional Oil

If you have a newer engine you have to use what they say in order to not void the warranty, and I know that some marine manufacturers specifically recommend against synthetic for some reason. I personally think that there could not be anything wrong with using a synthetic oil that is of the proper grade and proper type, and there is probably much to recommend it. For example, many of the very same engines that are used in boats are also used in land-based equipment, like commercial trucks, and many of those certainly use synthetics with superior results. One possible advantage would be an increase in engine hours between changes, which would reduce the amount of oil you need to carry with you on long trips. On the other hand, if you use a special oil it will be less likely you can find it outside of your home waters. I would check out Shell Rotella T6 5W-40 as a synthetic that is reasonable in cost (available at WalMart) and has a great reputation. I use it in my motorcycle.
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Old 12-07-2011, 19:04   #4
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Re: Synthetic Oil vs Conventional Oil

I've talked to an engine dealer and took a seminar and they recommend the synthetics, and pretty soon thats all that will be available. They are more expensive though.

One thing to keep in mind is that you pretty much need to go with one or the other, and not switch. If your engine has oil now, you can switch out I think, but going back to oil may not be a good idea.

thats all i remember.

Check engine dealer...also about warranty etc.
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Old 12-07-2011, 19:31   #5
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Re: Synthetic Oil vs Conventional Oil

Generally you should not switch from regular oil to synthetic. There are lot's of reports of the syn leaking by the main seals and running the engine out of oil. Synthetics are great if you start using them when the engine is new, you would have to check with the manufacturer regarding warranty.
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Old 12-07-2011, 19:38   #6
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Re: Synthetic Oil vs Conventional Oil

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Originally Posted by jrd22 View Post
Generally you should not switch from regular oil to synthetic. There are lot's of reports of the syn leaking by the main seals and running the engine out of oil. Synthetics are great if you start using them when the engine is new, you would have to check with the manufacturer regarding warranty.
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Old 12-07-2011, 19:39   #7
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Re: Synthetic Oil vs Conventional Oil

Synthetics are great at engine cleaning and therefore they gradually clean out old deposits if you have been previously using conventional oil. In some cases this can lead to leaks that were being blocked by the crud. However, modern synthetics are totally compatible with engine seals and will not soften them or cause ones in good condition to leak. For example, I recently switched my 1995 150,000-mile Mercury Grand Marquis to synthetic and my oil consumption declined significantly, probably due to cleaning out deposits that were causing leaks. So, yes it is possible to have a leak open up, but chances are it was there in the first place and it would have had to have been fixed sooner or later anyways. I wouldn't hesitate to change to a synthetic on an older engine. Here's a link that explains some of this.
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Old 12-07-2011, 19:46   #8
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Re: Synthetic Oil vs Conventional Oil

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Originally Posted by Kettlewell View Post
Synthetics are great at engine cleaning and therefore they gradually clean out old deposits if you have been previously using conventional oil. In some cases this can lead to leaks that were being blocked by the crud. However, modern synthetics are totally compatible with engine seals and will not soften them or cause ones in good condition to leak. For example, I recently switched my 1995 150,000-mile Mercury Grand Marquis to synthetic and my oil consumption declined significantly, probably due to cleaning out deposits that were causing leaks. So, yes it is possible to have a leak open up, but chances are it was there in the first place and it would have had to have been fixed sooner or later anyways. I wouldn't hesitate to change to a synthetic on an older engine. Here's a link that explains some of this.
yeha! Thanks!
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Old 12-07-2011, 19:52   #9
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Re: Synthetic Oil vs Conventional Oil

Apart from numerous reports that I have read about I have first hand experience with a case where a fairly new gas auto engine was switched to synthetic and lost most of it's oil out the front main seal in less than 20 miles of driving. Fortunately the engine was not ruined and when re-filled with regular oil it was fine, and never lost a drop of oil afterwards for 50,000 miles. Not a risk I want to take on my old boat engine.
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Old 12-07-2011, 19:53   #10
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Re: Synthetic Oil vs Conventional Oil

Yes but we're talking diesel. That does make a significant difference I think.
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Old 12-07-2011, 20:32   #11
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Re: Synthetic Oil vs Conventional Oil

Been using Amsoil since the mid 70's, long before the other companies ever heard of synthetic.

Have used in it cars, street and track, trucks p/u and real trucks, boats gas and diesel.

It's the only oil I use, extended oil changes actually make it cheaper than fossil oil. 25,000 miles in the cars, just change filters. 125 hours on my old Perkins. But it bulk and it's cheaper as is everything.
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Old 12-07-2011, 20:36   #12
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Re: Synthetic Oil vs Conventional Oil

<sigh> Most, if not all modern synthetics have formulas that not only WON'T harm the seals of your engine, they will condition them and make them seal better.

You CAN go from synthethic to mineral oil and back with NO harm to your engine or seals. A synthetic blend is just that, a blend of synthetic and mineral oil. This assumes both oils meet the manufacture's recommendations.

As a previous poster said, synthetics do clean up crud in your engine, and as most of you know from your shaft seals, if a seal is damaged, it generally doesn't "plug" itself with crud, it just gets worse, oil seals are the same. You see more leakage with Synthetics because the oils "slides" easier, i.e. see fuel economy.

Why use a synthetic? Better fuel economy, longer engine life due to less wear, less gunk in the engine because less wear and synthetic ARE much clearer than mineral oils. I could go on, and on.
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Old 25-11-2012, 21:35   #13
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Re: Synthetic Oil vs Conventional Oil

Another few points about synthetic lubes, and Amsoil in particular:
If you decide to switch to Amsoil (which is a true syntheic, not a re-formulated petroleum product-BTW), or any 'synthetic', you should do a thorough engine flush first. Amsoil has an engine flush the is very easy to use. Just add it to the old oil and run the engine at idle for about 20 minutes. Then completely drain the old oil. This will flush the carbon deposits and gunk out of the oil galleys and hidey-holes. A good idea is to keep the drain plug out for several hours, letting all the oil drain.

Then, replace the drain plug, and add the required amount of synthetic. Be sure to fill the new oil filter! Run the engine for a short time, to get a correct fill reading, and to check for leakage. Top off as needed.

One thing to think about, the high pressure filter (the one on the block) filters down to about 30 microns. Some are less. When you buy a filter, look at the filter itself, and it should have the rating printed on it. I wouldn't recommend any less than 30 microns.

I recommend a by-pass filter as well. There are several on the market, but Amsoil has a definite edge. For the heavy truck market, they have a by-pass that filters down to 2 microns. This is the same filter that is used on the Abrams tanks. The same element material is available on by-pass systems for smaller engines as well. It's a nano-fibre material that allows for superior filtration, but does not restrict oil flow.

A by pass filter is always installed on the 'low pressure' side of the system, sipping oil into the filter then returning it to the sump. The block (high pressure) filter has to allow the oil to pass through and climb the galleys, so it is much more 'porous', hence the 30 micron filtration. A good by-pass system will clean the entire sump in about 15 minutes.
Another advantage of a by-pass is that you now will never need to change your oil.
With the proper filtration, the oil will last indefinitely. The filters will need to be changed, and an oil sample sent to a lab, but the oil will not wear out. This is true even of organic petroleum oil.
The synthetics provide better cold start lubrication, better cleaning capabilities, and far superior heat dissipation.
I personally know several drivers with this by-pass system, and they each have more than 1 1/2 million miles on the oil, never having changed it.

I replaced the gear lube in my trucks transmission ( a 13 speed Fuller RoadRanger) and both differentials on the drive axles. The diff temps dropped more than 20 degrees, and the trans right at 20 degrees. That is significant. My diff temps on a 100 degree day, pulling a slight grade with a 30,000lb load was 162/159, respectively.

I have a 3 cylinder Perkins 8kw on board generator that allows me to have plenty of electricity in the truck. It provides power for A/C, heat, essentially I can be 'civilized. I run the 5-30 Amsoil in it, and I have 23,952 hours on it. It's never given me a problem. Perkins told me if it isn't smoking (it's doesn't) and is running well, keep it. Perkins makes a heck of a motor. It runs right at 1800rpm, and purrs.

Any questions about synthetics or lubricants can usually be addressed at Bob's website, a lubrication aficionado website Pretty interesting stuff there.
- Bob is the Oil Guy
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Old 25-11-2012, 23:52   #14
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Re: Synthetic Oil vs Conventional Oil

Before rushing out to buy synthetic oil for your boat, I suggest reading this:

Oil for yacht engines

Yanmar says that synthetic oil is extremely harmful for their marine engines; this guy Viv Cox, a sailor and professional lubrication engineer, agrees.
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Old 26-11-2012, 02:26   #15
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Re: Synthetic Oil vs Conventional Oil

Ditto Beta (Kubota). Do not use synthetic, period. Don't know why. Perhaps that allows the MLM hype to get its foot in the door.
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