Synthetic to non-synthetic, can you switch oil type?

[JDMEXforme]

So a car could go from Synthetic to Conventional and back to Synthetic?

[Nachtmensch]

here's a post from an MR2 forum i'm on. i figure it related to this topic well.

Originally Posted by Dijital357

There are a lot of misconceptions about Synthetic motor oils. I see it a lot here on mr2oc, and hear people talking about it elsewhere. The rumors fly.

First, let me state what this thread is NOT, before I get flamed:

This thread is not:
1. An advertisement for the oil products I sell
2. A comparison of any brands of synthetic or conventional motor oil
3. A place to ask questions about Amsoil products (please PM me)
4. A place to make unresearched claims about oil. Please research and post a link to a website where you have found your information, so you are backed up.

The links I post to back my answers MAY come from motor oil manufacturer websites. HOWEVER, I will NOT post any links from Amsoil’s website, so no one can accuse me of being biased toward my product!

Common misconceptions (other people feel free to ad to this list):

1. Can I switch to synthetic oil on an engine with many miles on it?
Links:
A: Mobil’s website
B: Krane’s Synthetic Oil Bible

Answer:
Yes, you can definitely switch to synthetic motor oil in a high mileage engine. The only possible draw back is an increase in the SIZE of any existing oil leaks. Basically it makes small leaks more noticeable. It in no way “causes” leaks. If you have huge oil leaks, fix them before you switch to save yourself some money..

2. Does synthetic oil CAUSE oil leaks?
Links:
A: Quaker state’s website (scroll to myth #5)
B: Castrol’s website (again, see myth #5)
C: Motorhome magazine

Answer:
I touched this in the previous Misconception, but no, synthetic oil does NOT cause leaks. The only thing it will do is make any existing leaks (big or small) leak more because it penetrates better than conventional oil does- and it will make really small leaks more visible (a blessing in disguise?). So if your car has an oil leak, fix it before you switch, save yourself some money.

3. Is synthetic oil THINNER than conventional?

Answer:
I’m not going to provide any links to this one. Modern motor oils (both synthetic and conventional) need to meet Auto manufacturer and SAE requirements for viscosity. 5W30 synthetic is 5W30. It is the same viscosity as 5W30 conventional. It has to be in order to have the SAE stamp of approval!

4. Can you use synthetic motor oil as a break in oil?
Links:
A: Mobil’s website

Answer:
Man, its really hard to find good articles on this, as you can see, I only found ONE. Most of the other stuff I found was forums arguing about it- pointless. Anyways, on to the answer: Yes, you can use synthetic as break in oil. As can be seen from the Mobil link above, many manufacturers are using synthetic as break in oil. This is a really highly debated topic, however. Honestly, I don’t think it really matters what you use. Synthetic certainly isn’t going to cause any damage during break-in, but neither will conventional. I know a lot of the guys on here who build engines will disagree with that statement, and I’m not looking to start a war!

5. Switching back and forth:
Answer:

A lot of the links I posted are from manufacturer sites. Why? They have the most concise answers. A lot of the other links I found for every one of these questions was to forums arguing. I didn’t want you all having to read through all that nonsense. Plus, if the manufacturers say it, and they’re wrong, they’ll have big lawsuits! So they’d better be right…

Like I said before, this is not an ad for my product, I hope I have made that clear in my effort to not use any links to Amsoil’s website, or even mention their oil. If you want to take it that way, you’ve missed the point!

I would like to invite anyone to ask questions, and comment on this. If you have a comment to make that adds to this list, or argues one of my points, please, post a link backing yourself up. Don’t make a blanket statement! Its a good way to ruin a good thread with pointless bickering.

I've heard once you use synthetic oil that you can't switch back to conventional oil. true/false?

Answer:
false. You can switch and swap all you want. You can even mix them. The only thing that will mess up your engine with todays oil is not checking the level and running out, doing 9-G turns with a stock oil pan with the rev limiter stuck at 11,000rpm, leaving your oil and filter in for 200,000 miles.

[Subdriver]

Originally Posted by JDMEXforme

A mechanic told me once you go with non-synthetic you can't go with synthetic. Is this true?

A lot of myths and half truths mentioned on this thread. Nachtmensch's post above addresses a lot of them.

My thoughts:
- Basestock compatibility. Most "synthetics" on the market today use a Group III, highly hydroprocessed mineral oil, base stock. As this starts as mineral oil, it is obviously compatible with non-synthetics. Higher end synthetics such as AMSOIL and Mobil 1 use a Group IV, polyalphaolefins or PAO, base stock. This base stock is also compatible with mineral oil. And Red Line uses a polyol ester, Group V, base stock, and again, this is compatible with mineral oils. Short story, the actual oils are compatible.
- Sludge cleanup. Synthetic basestock, particularly Group IV and V, has better detergent properties than does mineral oil. And, in general, synthetic oil makers use more detergents, primarily calcium. For example, look at the calcium levels of the AMSOIL 0w30 I use in my Cadillac CTS-V daily driver, and the Mobil 1 factory fill vs the labs universal averages on this used oil analysis report:
Cadillac CTS-V Used Oil Analysis – Mobil 1 5w30 vs AMSOIL 0w30
These higher detergent levels will clean sludge if you have sludge built up in your engine. For old, dirty engines, this might be a bad idea as the sludge can foul small orifices in the engine as it is cleaned out. If you go this route, a better option is to flush the engine with something like this:
AMSOIL Engine Flush
This will help clean out the sludge quickly before you damage your engine.
- Seal compatibility. There are many myths circulating regarding synthetic oils and seal leakage. Due to the significant variation in synthetic oil base stock, blanket statements about synthetic oils and seal leakage may be inappropriate. Many synthetics have a highly processed petroleum basestock. Others such as AMSOIL and Mobil 1 have a PAO basestock, which tends to shrink seals. And yet others, such as Red Line use an ester basestock which tends to swell seals. Most synthetics contain higher levels of detergents, which will clean sludge from seals exposing them to oil.

Most synthetics contain higher levels of detergents, which will clean sludge from seals exposing them to oil. Companies such as AMSOIL add a small percentage of Group V ester basestock to their oils to counteract the impact of seal shrinkage caused by the PAO basestock. The result is a fluid that will actually slightly swell seals (on the order of a few percent). But, if the seals are dried and cracked and the higher levels of detergents in the synthetic cleans the sludge exposing these dried and cracked seals to oil, it will likely leak. For those that have never used synthetic and may have really old seals, you might want to stay away from synthetics. For others, who kept their oil clean and prevented sludge buildup, synthetics shouldn't negatively impact your seals.

If you have a clean engine and you are experiencing no leaks, then you should not have any leaks with AMSOIL or other quality synthetics. On the other hand, if the engine contains sludge due to age or inappropriate maintenance practices, you may experience a temporary leak. When the seals have gone for sometime without oil contacting and nourishing the seals due to blockage from sludge, they will harden and shrink. Since most synthetics, including AMSOIL, contain a significant amount of detergents, they will clean and remove this sludge exposing dried out seals to the oil. Depending on the synthetic oil used, this leakage may or may not be temporary. AMSOIL uses other additives such as Ester which will improve the seal’s suppleness and counters the shrinkage of the PAO basestock Based on reports I've read, AMSOIL should swell the seal 3% to 5%. But, if the seal has a mechanical fault, such as a crack or tear, then AMSOIL can't repair the damage. How other synthetics effect the seals is highly dependent on their basestock.

[Nachtmensch]

i was waiting for you to chime in

[Subdriver]

Originally Posted by Nachtmensch

i was waiting for you to chime in

Sorry I was slow.

Had a busy weekend, getting ready for a race this upcoming weekend in Portland, so I missed the start of this one. Looking forward to being back on the track though.