Synthetic Oil Change Frequency

[bstreep]

I wouldn't think of going 25,000 miles with ANY engine oil - AMSOIL or not, in any of our vehicles. We run mega-expensive synthetics in 3 of our MB vehicles ($8/liter) - and STILL change them at 10,000 miles.

[LakeSuperior]

25,000 miles or one year was/is the recommended drain interval by Mobile Oil for their Delvac I synthetic for passenger cars. I suspect a fair amount of data was collected to support this recommendation. I also believe a good safety factor was built into it.

[Mule]

Originally Posted by LakeSuperior

25,000 miles or one year was/is the recommended drain interval by Mobile Oil for their Delvac I synthetic for passenger cars. I suspect a fair amount of data was collected to support this recommendation. I also believe a good safety factor was built into it.

Yeah, I know what you are saying, but ya know, I just can't do it. I just was not raised that way.

The new diesel wagon, Jetta is coming up on 5k, book says 10k oil changes. I do not know if I can go 10, I am already getting nervous and breaking out in hives just thinking about 10k, as for 25k...well just shoot me now, dig a hole and roll me in it, just can't do it.

[Highlander40]

Along with the longer interval, Amsoil recommends using EA oil filters(yes an Amsoil product) It is a micro fibre fabric that will hold more dirt before clogging up. I have used similar depth style filters in industrial applications and the life is several times that of a standard pleated paper.
Relating to marine diesels- A second oil filter called a bypass filter will also extend the oil change interval. It is much finer than the main filter and only a portion of the oil flow goes thru it. My Yanmars have them as standard equipment with a 250 hour interval.

I have a small diesel generator. Single cylinder, no oil filter. inside an enclosure. oil capacity 1 qt. This is a perfect aplication for synthetic oil. Lots of heat and the oil must suspend all the dirt.
Regular oil vaporizes and thickens, Amsoil doesn't.

In my cars, mileage is not an issue but I like changing oil once a year and I'm done. No standard oil will be stable that long.

[hellosailor]

"In my cars I have seen no benefit to synthetics and only detrimental stuff like pesky oil leaks."
Maine, have you done a teardown and compression tests on those engines? I've only got 100k miles on my riceburner, which has run the radical new Mobil1 since 1985, when it was indeed radical and new. Engine still has full compression and zero leaks, zero oil consumption.
I went synthetic way back because I had the full press kit from Mobil. Guaranteed that there is coke and tar forming on your valve covers and in other places in the engine with any conventional oil, because the heat breaks them down. If some of that tar gobs off and blocks an oil passage, you have catastrophic lube failure and you lose the engine.
With synthetics? No tar, no gobs, no such failure mode possible.

The synthetics also are premium oils from the start, so the makers do indeed load them up with more additives and more expensive additives than the $1-a-quart oils have. When I sent mine out for analysis the first time, it came back heavy with molybdenum. I couldn't figure out why, because I'd never added moly to my engine. But it turns out, Mobil DOES add it, they just don't talk about it because additive blends are a competitive secret. What else is in there? I don't know, I just change it once a year and give it to someone else whose car does burn a little oil. What I give him is still cleaner and slicker (by finger test) than what he runs normally. It still tests out 100% meeting original spec. As it should, since it is a year old, but way below the mileage/use threshold.

[Highlander40]

Way back when, oil seals were not as good as todays. Unless you start with synthetics , the varnish and gunk work loose and that may be the only thing keeping the oil in.
With a modern engine, oil leaks are not related to the type of oil.

[aspiringsailor]

my $.01
Mobile 1 says it provides up to 15,000 miles and just has an exclusion for heavy uses. Amsoil says 25,000 for normal/15,000 heavy. I personally use Amsoil. even though it says up to 25,000 i just skip an oil change and change it at the next interval no matter what it says it can do. And i also use the amsoil filters.

[Chief Engineer]

Is Amsoil part of Amway?

[svcattales]

Originally Posted by Chief Engineer

Is Amsoil part of Amway?

Chief, I looked at Amsoil's website and didn't see any mention of Amway.

OBTW, there's and interesting testimonial on their web site. A guy ran a Mack truck for 409,000 miles on Amsoil without an oil change. They tested oil periodically and it remained in good condition. At the end, they tore the engine apart and there was no excessive wear.

I'm leaning towards doubling my oil change interval on my Volvo diesels based on what I've read on CF and internet. Diesel trucks are getting very long change intervals on synthetics and testing shows oil is still in good shape. I know that many have said that "boat engines are running uphill all the time", but isn't that a better for a diesel than stop and go traffic? Boat diesels at cruise RPM are doing what keeps them healthy... running at high load factors and maintaining constant internal temperature. Also, one of the highest wear factors on any engine is the number of start cycles. Starting should be the only time there is metal to metal contact. When I start my boat diesels, they often run all day and then shutdown. One day, one start. When I run errands in my car, I may start it 5 times/day.

So do marine diesels REALLY need more frequent oil changes than a Peterbilt or your "family truckster?" I'm not convinced.

[hellosailor]

Amsoil may have no relation to Amway, but google "Become Amsoil Dealer" and a funny thing happens. Their business seems to consist of selling the business, as much or more so than selling the oil.

Could be great oil but that kind of thing turns me off.

[ArmyChief]

Greg,

In another thread you were getting a oil analysis done. How did that turn out?

[anjou]

Diesel oils have detergent in them to keep the engine clean of carbon. So if your Amsol is staying cleaner, is it doing a good enough cleaning job?

I use synthetic in my VW cos thats whats called for and its turbo'd. The last thing I need is a turbo failure.

As for boat engines, who decides the 'how many miles to run time hours' ratio to compare like for like?

Im not all together sure a marine engine works harder than a car engine. It doesnt do stop start or acceleration like a car does. No short run times that dont let it reach opperating temp, not like a car doing the school run.

Im getting mixed messages about this synthetic, some say it stays cleaner while others say it holds particles in suspension better.
It cant do both.

If it is holds particles in suspension, how well does it give them up to the paper filter, cos after all, thats the filters job?

If its holding all that muck in suspension, how well is it cooling and lubing?

On the other hand, if its not getting dirty, is it cleaning away the carbon or letting it deposit, ready for a soot fall and a blockage?

[LakeSuperior]

Originally Posted by anjou

Diesel oils have detergent in them to keep the engine clean of carbon. So if your Amsol is staying cleaner, is it doing a good enough cleaning job?

I use synthetic in my VW cos thats whats called for and its turbo'd. The last thing I need is a turbo failure.

As for boat engines, who decides the 'how many miles to run time hours' ratio to compare like for like?

Im not all together sure a marine engine works harder than a car engine. It doesnt do stop start or acceleration like a car does. No short run times that dont let it reach opperating temp, not like a car doing the school run.

Im getting mixed messages about this synthetic, some say it stays cleaner while others say it holds particles in suspension better.
It cant do both.

If it is holds particles in suspension, how well does it give them up to the paper filter, cos after all, thats the filters job?

If its holding all that muck in suspension, how well is it cooling and lubing?

On the other hand, if its not getting dirty, is it cleaning away the carbon or letting it deposit, ready for a soot fall and a blockage?

Recommend going to the websites like Mobile's and reading up on how oil really works.
For example, the flash point of Delvac I is about 100 deg F higher than regular oil. That means the synthetic oil will lubricate higher up on the cylinder wall than regular oil. This also means reduced oil burn on the cylinder wall which corresponds to less soot (carbon) generation.

Also, look at the benefits synthetics for cold starts. The flat viscosity curves are significant for the enhanced performance.

A car at 55 mph might be using 15 to 20 percent of rated HP at 2500 RPM. A boat engine may be developing 80 to 90 percent of rated HP at the same RPM. Boat engines work many times harder than car engines.

[Healer52]

A very good site for all things lubricative is
Welcome

More info on oil than I know what to do with.

BTW, I have several diesel vehicles and use regular dino oil in the crankcases...but we change the oil and filters regularly (at 5K miles). Synthetics everywhere else.

[hellosailor]

Anjou, I'd also suggest going to Mobil and Shell and such to ask about the details of lubricants. The first question is to make sure you are using an appropriate oil for your engine type (spark or compression) and usage (pressurized aviation engines versus normally aspirated ones at sea level, more or less) because they have different needs and are formulated differently.

Bottom line is that these are their premium products with most & best additives, not just built on more extensive stock. Removing soot and particulates will depend on your filter, they range from 2-11 micron pore size typically, so the right one can make a big difference. Then again many diesels are built with loose rings, with the intention that they will consume oil, forcing you to add new oil and keep topping it up--which also dilutes the soot that was in it.