Gman91932

Does using synthetic oil make any difference? I always wanted to ask but did not know where to ask.

jswedberg

Synthetic oil can extend your interval between oil changes.

I think a good "regular" oil and a good synthetic will both keep your engine lubricated well.

Synthetic is one reason new MBs have such extended service intervals (~12K miles on our ML)

I was told that using synthetic on an older car (don't know how old your is) may bad for the seals - The Porsche dealer told me NOT to use synthetic in my '88 911, for instance.

suginami

If the car has never had synthetic oil before, then I wouldn't put it in.

I've read too many instances where synthetic caused a lot of oil leaks.

csnow

I have found that synthetic oils tend to be 'consumed' significantly faster than regular oils or blends. I do not know if this is because it damages or alters the seals in any way, or if it is something about the properties of the oil itself. One researcher in one study claimed that the extra 'slipperyness' of the oil simply makes it more likely to pass by the seals and rings. Of course, the W124 has an oil level warning light, so we are less likely to be surprised.

I have seen many comparison tests that have shown no difference in engine wear at all. Consumer Reports did a comprehensive study using Taxi cabs over hundreds of thousands of miles. Unfortunately, none of the studies I have seen have really tested whether or not there is a substantial 'cold startup' advantage given the lower viscosity of synthetics at lower temps. Most experts seem to agree that the bulk of engine wear happens between the time that an engine starts and oil pressure is attained.

Unable to decide if it is worth 4X more for synthetics, I have settled on synthetic blends as a compromise.
In New England, the salt always gets my cars before the engines wear out anyways.
I once took apart a BMW 3.0L engine with 170K miles because the head gasket had blown. The oil had been changed religiously using regular oil, and there was no significant wear to be found. There was not even a noticable ridge at the top of the cylinders.
The intake valves were a little warn, but not bad.
This was amazing, at least to me, since I had typically dissected similar engines that had not been maintained so well.

Budonkadonk

DOH!

Rule #43: Never ask about synthetic oils on an online forum.

Just kidding...

I use Mobil 1 and have always been impressed with it. However, switching to synthetic can be risky if your car has always been fed dino oil. If you drive a car that is less than 10 years old, I'd feel pretty safe about throwing some synthetic in there.

Anything older than 10 years, and its a judgement call--green light if the engine has been well maintained and has always gotten frequent oil changes with GOOD oil (such as Mobil or Castrol).

As a preventative measure, make sure the PCV system is free-flowing on an older car. Buildup of crankcase gasses can put stress on seals and cause them to leak... it gets worse with the extra-slippery synthetic juice.

Good luck!

-Joe

MDV Synthetics

I'm glad to see you noticed the shortcomings of the CR study in the cold start area and recognize the importance of this. As for the oil consumption, I can help clear up some of the reasons why the oil is "consumed". There is a test called NOACK volatility, which measures the weight loss in percent of the oil due to evaporation when exposed to high heat. First off, conventional oils tend to have a NOACK volatility of 20-25%, but the lighter parts of the oil burn off first, leaving the heavier "sludge" behind, making the oil less likely to seep past areas like the rings. The downside to this is that the heavier oil now doesn't protect as well. Synthetic oils have lower NOACK volatility scores, so they are more likely to hold up in high heat situations but they are more likely to seep past the rings and be burned off there.

However, not all synthetic oils are created equal. Mobil 1 10W-30 has a NOACK volatility of 14.98%. Amsoil 10W-30 has a NOACK volatility of 6.9%, so it is much less likely to be "boiled" off in severe use. Coincidentally, this is how Amsoil can help you reduce your emissions and oil consumption. Less evaporative loss of the oil leads to less of the oil being burned and going through the exhaust system. More info on the different properties and classifications of motor oil can be found at http://www.mdvsynthetics.com/guides/functions.htm

Mark

csnow

Mark,
Interesting angle.
Who says there is nothing more to discuss regarding synthetics...

I had not really considered evaporation as a significant factor in oils this viscous, but it makes sense, particularly considering the high temperatures involved.

It is obvious to anyone who does oil changes that motor oils thicken with use.
I had always assumed that engine oil got thicker over time due to a combination of 'thermal breakdown' (scorching), particulate matter from exhaust 'blowby' (carbon and other stuff), and metal particles from wear. A 20%+ evaporation rate would be a very significant contributor here.

MDV Synthetics

The interesting thing about synthetics, unlike conventional oils, is that the technology involved in them is constantly changing. I think this is especially important considering the pace of development in our modern engines, which put more and more demands on the oil. Just looking at Mobil 1, they are on their 3rd formulation in 10 years. I get the feeling we will all be arguing about this topic for many years to come.

yhliem

to corroborate what mark is saying, in less scientific terms , is that synthetic oils are NOT the cause of leaks.

There is nothing wrong with switching over to a synthetic if you've only ever been on dino oil.

HOWEVER, if you've ever compared the two, you will see that 40 weight synthetic oil is considerably thinner than 40 weight dino oil.

Because of this, you may NOTICE more leaks. Again, these leaks are not caused by the change in oil. the leaks were moslt likely always there, but not noticable because the thicker dino oil wouldn't leak out as easily.

you CAN switch over at any time, but be aware that you may have to get your engine re-sealed if it is an old engine.

(i'm a physicist, not a chemist :p) hehehe

Now, to throw my $0.02 in about the debate...

people using synthetics are right.

people using dino oil are right.

you are BOTH right....IF you change your oil and filter regularly. and i mean regularly to the point of scheduling your life around the oil changes.

personally speaking, i change my oil every 4000km...which is a bit under 3000 miles. because of the frequency of my oil changes, i cannot justify spending twice as much monesy so i can use a synthetic blend.

the major advantage to the average person for going to synthetics is longer intervals. since i have no intention of stretching my intervals out (that sounded kind of sick) I gain nothing by going to a synthetic.

the BEST thing you can do for your car is to change the oil regularly and often. PERIOD. synthetic oil or no, if you leave it for too long, you've spent twice as much money to get to the same result.

MDV Synthetics

There is a tool called oil analysis, I think I saw someone else onthis board mention it to, that can tell you the condition of your engine and the oil by looking at the used oil. It can be also be used to tell how much of the additive package the oil has left in it, giving you a better idea of how much longer the oil can be in use.

One of the samples I sent in with with Mobil 1 5W-30 in the crankcase for 8060 miles. My driving conditions included mostly highway trips with several sessions of WOT driving on 2 roadcourses in the Northeast and several autocrosses, so the oil worked very hard. The second sample was after I switched to Amsoil 5W-30 under similar conditions for 8K miles. While both oils held up very well under those conditions, it was apparent that the Mobil was nearing the end of it's life while the Amsoil still had plenty of life left. All wear metals were below average in both samples, indicating the oil was not contaminated with insolubles that could cause me a big headache later on down the road.

Some people over on maxima.org have started an oil analysis spreadsheet to monitor how different vehicles under widely variable driving conditions with numerous types of oils hold up in real world, not laboratory conditions. It's very interesting reading. It can be located at http://forums.maxima.org/showthread....hreadid=100060 or http://www.mdvsynthetics.com/analysisintro.htm

MDV Synthetics

Here's some more on seal issues:

AMSOIL lubricants are all tested for seal compatibility with all the seal materials in use with industry accepted testing methods. AMSOIL Products will not damage seals or be more prone to leaking than petroleum products when used in vehicles with undamaged seals. Unfortunately, high mileage vehicles and equipment that have been using petroleum lubricants for long periods of time face the risk that sludge and deposits have built up in the engine and created a false seal, and the seal itself has dried out and cracked or shrunk. Lubricants help condition seals, keeping them supple and slightly swelled to insure a proper seal with no leaks. When covered with sludge or deposits, the seal will deteriorate. Now you start using AMSOIL motor oil with it’s high quality additive package and natural detergency, and you start to clean up the engine. The false seal is cleaned away, and if the seal itself has become cracked or damaged, a leak will develop. The same thing occurs in transmissions and differentials. Because of this, many people think that synthetic oil is more prone to leaking, when all it really is doing is revealing the problem that petroleum oil deposits had created and kept hidden. Once the damaged seals are properly replaced, keep using the synthetic oil and they won’t leak again.