Synthetic vs. Regular Oil?

Synthetic oil gives much better lubrication when very cold, better resistance to oil deterioration when very hot, very slightly better fuel mileage, cleaner engine, longer oil life, slightly less wear due to the higher film strength if it is a PAO synthetic. Disadvantage...cost.

Oil life?...If it is a top quality synthetic, much longer. You're good for at least the maximum oil drain interval shown in your owner's manual, but you really only know by getting lab oil analyses. There are different quality synthetics. The best I've seen are Mobil 1, Red Line, Amsoil, Schaeffer. Lowest quality are Wal*Mart and other cheapies. Synthetic blends? Except for Schaeffer, save your money.

Some folks talk about leaks. That sometimes happens due to the superior detergents in top quality oils, but unless the leak is caused by a ripped seal or some other mechanical reason, it'll stop within one to three oil drain intervals. No problem with higher mileage engine, but if you don't plan on owning the vehicle just about forever, why switch?

Ken

Steve

Forgive me for the following, but I have this summer cold and really have nothing else to do but wheeze and hack and drink tea to then wheeze and hack some more.

What is synthetic oil: In the simplest terms, is a oil that is made up of either polyalphaolefin (PAO) or polyol esters (POE), or a combination of the two. PAO is created by the catalyzed synthesis of low-cost propylene (C3H6) and/or ethylene (C2H4) gas, low cost in that they are a product of the distillation of crude oil. In fact, those gases were once flared at refineries as a waste gas, but that's another story. POEs are made by the reaction of a family of weak organic acids with specific long-chain alcohols. Both PAOs and POEs together or separately make up synthetic oil as we know it, the majority of the synthetic motor oils are a blend of the two in some ratio that varies from company to company. For instance, Mobil 1 is essentially a polyol ester based oil whereas Redline is a blend with more PAOs. Both PAO and POE are highly tolerant of heat, both are essentially unaffected to temperatures up to 240 C (465 F). In addition, both tolerate high pressure and shear, generally reassembling when the structure is broken. Additive packages, including plasticizers for multi-viscosity and detergents are added to the synthetic oil after creation.

What is conventional oil: Conventional motor oils are mineral oils manufactured by the refining of the distillation of crude oils with further refining in separate columns at the refinery in order to get the largest percent of the target carbon range. In essence they are optimally saturated single bond carbon chains of a specific carbon range. In a very simplistic sense, think of a really fatty cooking oil and that's the motor oil. Contaminants, meaning hydrocarbons in the carbon range but lack the suitable characteristics as a lubricant include 5- and 6-carbon aromatics, carbon chains that are either longer or shorter then the optimal range, etc. Conventional oils are not as tolerant to heat, beginning to breakdown at 100C (212 F). In addition, the single bonded carbons are far less strong as the ester and olefin chains of synthetic oils. Additive packages, including plasticizers for multi-viscosity and detergents are added to the synthetic oil after creation.

Pros and cons of synthetic oil:

Pros

1. substantially higher heat tolerance before oxidation onset. Recall the old Mobil 1 commercial where the pans of oil are fried. Well, it's true. Try it yourself.
2. much higher tolerance for shear effects, in fact, sheared chains tend to reassemble themselves into the same original structure.
3. both PAO and POE tend to smear on hot metal whereas saturated hydrocarbons tend to bead
4. much higher film pressure capability
5. able to buffer (neutralize) acids for a longer time
6. both being highly resistant to emulsion, in fact, esters excel in this function. In other words, able to "carry" water without foaming and separating out
7. flow at much lower temperatures, down to -50 C.
8. resist viscosity changes to higher temperatures
9. tolerant of long drain intervals, i.e., 7000-12,000 miles of typical highway driving without any appreciable degradation.
10. this hopefully isn't an issue however, most synthetics biodegrade rapidly in soil versus conventional oils that take up to 16 times longer in the same conditions.
11. clean synthetic oils have a substantially higher LD50s then comparable conventional oils.

Cons:

1. Cost, a quart is roughly 3 times more over a comparable conventional oil.
2. Synthetics, primarily POEs have a tendency to dissolve buildup, leading to oil leaks in older engines. This doesn't mean synthetic oils cause oil leaks, the leak was always there but plugged up by buildup which the synthetic oil dissolved. Switching could cause premature oil filter plugging if the engine is really dirty with sludges and buildup, particularly the gunk that resides in the bottom of the oil pan.

Both synthetics and conventional oils are easily recyclable.

There, hope this helps. Personally, I've always used synthetics and finally got myself to extend the change interval to 5000 miles, but it wasn't easy. I can't see why conventional oils can't be used with a yearly engine flush though really, it's cheaper to use synthetics and leave out the flush. But, then again, that's my opinion and others are equally valid if not more so.

Question...

In the case of using the synthetic on an older engine.. whats the better way to flush the engine before starting usage? Or is it just as well to start and just change the filter couple times in between oil drain?

temperatures

What a great response! Although some of the technical stuff was a bit over my head, there was enough of it to convince me to start using the synthetics in my new Tacoma. Should I start right away or wait for my first scheduled oil change? Do you have a suggestion on which brand is best? What about oil filters, are they all created equal?

Thanks again for the great response and I hope your summer cold gets better soon.

temperatures

I change my Mobile 1 synthetic oil in my 03 truck every 5,000 miles, mainly because it's still under warranty and Toyota calls for a 5,000 oil change. At 5,000 miles the oil looks in good shape, it's a dull orange, not black like dino oil gets. Now I have 19 yo 1985 toyota truck too, what harm, if any would be done if I put my 5,000 used mobile

Don't bother flushing, it would only create more potential problems from introducing chemicals to the oil system - and the flushing agents are not lubricants. Just change the oil when the motor is warm (wear gloves when removing the plug and get your hands out of the way) and give it 20 minutes or more to let it drain out thoroughly.

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I have his message marked "Save" for future reference, too. Good stuff.

On a new car or truck, change the oil once or twice with regular "dinosaur oil", and wait until you are sure the piston rings are seated and the engine isn't using any oil. Between 5,000 and 10,000 miles is a good range.

Synthetics are much slipperier, which is why you want to use them - but the piston rings need to wear in a bit to seal properly, and for the oil control ring to scrape off the excess oil film off the cylinder.

Change to synthetics on a brand new production-line engine, and it may take a lot longer for this to happen, and it'll be using more oil until this necessary wear happens. There are custom cars that use synthetics as factory fill oil, but they also hand-build those engines and they spend a lot of extra time to hand-hone the cylinders to a mirror finish and lap the rings during assembly, then they test run the engine on a stand to make sure it's right.

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that's what i do. i take the mobil 1 out of my '99 subaru every 3k miles and then it goes in my '89 4runner for another 3k miles and then it goes to the recycling plant. in my saab, i never change the oil, just change the filter every 3k and add 1/2 quart or whatever to top off. the saab has 180k miles and the 4runner has 233k, neither burn or leak a drop of oil. the subaru only has 50k miles, so i can't say anything about that yet.

Bruce has a point about introducing some chemicals into the system when flushing an engine. Engine flush material varies but most are Stoddard's solvent, napthene, and a host of other things, most commonly a sulfonate of some kind. In the past people used kerosene and oil, and I've heard that automatic transmission fluid and oil being used. Either way, the purpose is to dissolve the sludges in the pan and channels, as well as dissolve the ash and varnish in the upper galleries.

This is the way to properly flush an engine:

Dump the oil. Close drain plug. Add a quart or two of an engine flush. Fill the remaining amount with cheap oil to make up the fill capacity of the engine without changing the filter( look in the owners manual for capacities, usually in the back).

Start engine and let idle for a minute and turn it off! Do not rev the engine or run more then a minute. The engine flush is a solvent and not a lubricant. The idea is to circulate it around the engine and mix gently.

Go in and have a cup of coffee and do something for an hour or so then

Start engine and let idle for 30 seconds or so. Do not rev the engine or run more then a minute. I just have to emphasize the time once more, forgive me.

Go in and do something for an hour or so.

Repeat the start and turning off, then dump the oil. It'll be pretty nasty as you'll discover. Put the drain plug back and fill with cheap conventional oil to the fill capacity of the engine without a filter change as earlier. The idea is to dilute and flush out whatever flush remains in the system in the new oil, being held in suspension.

Start it up and drive around neighborhood for a few minutes then head home, let the engine cool down a bit then dump the oil and change the filter. Add whatever oil you like. That's how to flush an engine.

BTW: the flush and dirty oils are totally recyclable. Take to your local recycler. Whatever you do (addressing to everyone) NEVER put a chlorinated solvent in motor oil. What happens is that this makes the batch of oil hazardous and expensive to dispose of.

So there you go.

polyalphaolefin

Please forgive me for the delay in responding, between the cold, which is a now a thing of the past, the boat also clamored for attention. Then there was the 4th. Hope yours was good.

So, to answer...first of all, there's a break-in period. There's some merit in using dino oils for a few thousand miles and/or a couple oil changes. I've always been a paranoid about new engines and trannies and changed the fluids in the first couple hundred miles with the same fluid that was in there for the most part, then switched over to pure synthetics after a couple 3000 mile interval changes for the engine , and at the second change, changed everything. Then again, I've been told that there's a special break-in oil used. Then again, when I've tried to find out what this special break-in oil is, I've found that it's regular oil, so...I'm hoping someone with some info on what this stuff is would reply.

We've always used synthetics when they came out (too many) years back for cars and trucks. The benefits far outweigh the expense however, one can always use dino oils and flush the engine every few years and be just fine, too. After all, we have Toyotas, and they last and last just like the Ever-ready bunny. Seriously, in my opinion and to risk starting a forest fire of flaming...

We use Mobil 1 since one can save a couple bucks by buying the 6-pack case at Costco. Mobil 1 has the lion's share in total sales for synthetics as well as by volume. Mobil 1 oil is 100% synthetic, based on polyol esters. There's also Amsoil, Redline, Valvoline and I guess a few others, too.

For filters, we use the Toyota oil filters. We have a friend who works in the parts department of a Toyota dealership in San Diego who gives us his cost for filters. A while back the American Petroleum Institute (API) did a study of oils using a couple new cars and the factory oil filter. It turned out that Toyota has a real good oil filter series. So that was obvious which filter to use. Knowing Doug has saved us quite a bit of money over the years.

Fram filter...there's something scary about the three grades filter quality...kind of implies issues in QA/QC.

So, there's my two cents, and thanks for your kind words. I hope this helps. There's some seriously smart people with serious experience and knowledge on this NG and I'm sure there's other thoughts and insights, too.

polyalphaolefin

Bruce

Good info, thanks. Got a question: I've been told that the initial oil put into vehicles helps in the break-in process, implying that this oil is something special or specific for the function. Is this true?

BTW: thanks for the comment on my wandering babble about synthetics, all of you are far too kind. That badly written thing is the result of an undergraduate degree in mechanical engineering and later a doctorate in atmospheric chemistry. There's more in my alphabet soup of letters, but who cares. I really should have spent time and added .jpg images of the single chain alkanes versus the lattice structures of the synthetics. Maybe added something on the relative strength of each? One of these days I'm going to get around and collect the details on the additive packages being used in oils, too.