# Using synthetic oil



## Jim McC (May 22, 2013)

Once synthetic oil is used in your car, can you go back to regular oil? Or do you have to keep using synthetic ?

Thanks.


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## woodchopper65 (Mar 28, 2016)

you can go back, use a mix of both, doesnt matter...


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## Windows on Wash (Aug 30, 2011)

You can go back.

The bigger issue is usually if you are running conventional and switch to synthetic after a while. If you have a leak with conventional oil, it will gush worse with synthetic.


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## paintdrying (Jul 13, 2012)

Friend of mine was bragging he has not changed his oil in 30,000 miles and it looks brand new. I was sold, went out spent a small fortune on oil. I changed it at about six in the morning and by noon the next day I had hardly any oil left. That was maybe 20 years ago and I have stayed away from synthetic ever since.


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## gregzoll (Dec 25, 2006)

All that we use in our vehicles is a Synthetic for high mileage. Some Synthetics you can get away with not changing for a long time.


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## gregzoll (Dec 25, 2006)

mj12 said:


> Friend of mine was bragging he has not changed his oil in 30,000 miles and it looks brand new. I was sold, went out spent a small fortune on oil. I changed it at about six in the morning and by noon the next day I had hardly any oil left. That was maybe 20 years ago and I have stayed away from synthetic ever since.


The low oil was not from changing the oil. It was from not checking the fluid levels, which a lot of people are guilty of.

I have gone up to 12,000 miles between changes with the Synthetic High Mileage that we use in all three of our vehicles. I may have to put a quart in after a couple of months, since two of our vehicles are mostly in town driving. Have had no issues with anything else.

All engines use oil during the firing process, because each time the piston takes a stroke or the valves open, there is going to be a small amount that gets into the chamber that gets burned off during the firing process.


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## Bret86844 (Mar 16, 2016)

Synthetic oil is great stuff. It's my understanding the oil itself lasts a very long time and really it's the filter that ends up needing changed first. 

A lot of cars that come from the factory with synthetic have recommended maintenance intervals of 10,000 miles or more.


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## gregzoll (Dec 25, 2006)

Bret86844 said:


> Synthetic oil is great stuff. It's my understanding the oil itself lasts a very long time and really it's the filter that ends up needing changed first.
> 
> A lot of cars that come from the factory with synthetic have recommended maintenance intervals of 10,000 miles or more.


People do not realize that it was Germany and Japan who created Bio-Diesel and Synthetic oils during WWII. Synthetics have been around since WWII, when all countries had to look at alternative oil and fuel sources, if they were not able to keep a supply coming in.


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## gregzoll (Dec 25, 2006)

Windows on Wash said:


> You can go back.
> 
> The bigger issue is usually if you are running conventional and switch to synthetic after a while. If you have a leak with conventional oil, it will gush worse with synthetic.


That is actually false. Synthetic blends allow an engine to be able to not burn off the oil at high temps. It has nothing to do with how fast oil leaks if a seal goes.

Japan and Germany perfected the use of Synthetic Oils during WWII. Over time, Synthetic blends have gotten better, that they are now able to save on how much recycled conventional oil and refined crude's for oils.


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## Jim McC (May 22, 2013)

Thanks guys


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## Windows on Wash (Aug 30, 2011)

Bret86844 said:


> Synthetic oil is great stuff. It's my understanding the oil itself lasts a very long time and really it's the filter that ends up needing changed first.
> 
> A lot of cars that come from the factory with synthetic have recommended maintenance intervals of 10,000 miles or more.


While you can run longer intervals on synthetics if the base numbers and additive packages are correct, the filtration of the oil isn't the limiting factor in many cases. 

AMSoil does sell a remote dual filtration unit that keeps the oil darn near clean, but the additive and base numbers are what typically create the necessity to change the oil in a car. 



gregzoll said:


> That is actually false. Synthetic blends allow an engine to be able to not burn off the oil at high temps. It has nothing to do with how fast oil leaks if a seal goes.
> 
> Japan and Germany perfected the use of Synthetic Oils during WWII. Over time, Synthetic blends have gotten better, that they are now able to save on how much recycled conventional oil and refined crude's for oils.


Synthetic oils do, on average, have higher TFout numbers which limits their burn off and volatilization, however, I was speaking more to leaks at rubber seals and other gasket surfaces and not any consumable aspect of the oil. 

Synthetic oils are usually both slipperier and smaller. If you have a seal (assuming that it is a post 1992 motor with seals that are rated for use with synthetics) that is leaking with a dino oil, it will leak faster with synthetic. 

http://www.cenex.com/about/cenex-in...page/oil-and-lubricants/five-engine-oil-myths
_
This is an often-cited myth. In fact, if your seals and gaskets are in good condition, synthetic oil will not leak in your engine. Synthetic oil has not been shown to deteriorate engine seals or gaskets. But it might find an existing leak. The smaller molecules of synthetic oil are able to pass through very small cracks and crevices that the larger molecules of petroleum-based oil cannot. Eventually, those small cracks and crevices can lead to bigger problems — with or without synthetic oil. 

_http://www.aircooled.net/synthetic-vw-oil/
_Synthetic oil causing oil leaks is another commonly spread myth. The truth of the matter is that if all your engine seals and gaskets are in good condition, synthetic oil will NOT leak in your engine. The myth started because on occasion, an engine will leak with synthetic oil, but not dino oil. The reason for this is that the smaller molecules of the synthetic are able to get past very small crevices, where the larger molecules of dino oil cannot. But this does not mean that the synthetic oil has caused the leak, it simply has “discovered” an infant leak, and regardless of what oil you are running, this infant leak will eventually grow to a size that will allow dino oil to occupy and pass also. Synthetic oil has not been shown to deteriorate engine seals or gaskets. It is not some evil solvent that will break down sealant, or anything like that. Like was said earlier, it is just a man-made base stock, that is uniform and smaller in molecule size than dino oil. Nothing more, nothing less._
I have seen cars that showed no signs of leakage start leaking with synthetic oils. Now, this could be a function of several things that all existed prior to the synthetic oils, but the combination of the smaller and more slippery molecule can manifest as a leak.

Synthetics tend to have a better additive package as well and I have seen motors that were previously run on conventional oil get "cleaned" by the higher end synthetic. In doing so, it scrubbed out some of the sludge that was previously band-aiding the seal that now started to leak.

Again...none of these things are the fault of the synthetic oil and I still run them in every single one of my cars, but the potential for a more significant leak where one already exists is definitely there with synthetic oils. 

Very reasonable trade off in my opinion based on the better performance.


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## Brainbucket (Mar 30, 2015)

Rule of thumb. You can go from synthetic to conventional oil but not from conventional to synthetic as synthetic washes the engine and it will wash the conventional oil debris to the sump and stop it up. See it too many times. If the engine doesn't have too many miles, rule is moot but if you do, rule isn't. jmho:vs_cool:


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## Jim McC (May 22, 2013)

But going back and forth with conventional oil and synthetic blend is no problem?


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## Windows on Wash (Aug 30, 2011)

The question becomes...why would you? Synthetic is not that much more than good quality conventional in many cases.

Walmart has great deals on Mobil 1 in the large containers and if we are talking about a 6 quart engine, you would save about $12-18 per oil change if all other things are equal. 

That is $1.80 per 500 miles. That's a pack of gum. 

With how expensive motors and components are today, seems like a wise investment to me.


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## Jim McC (May 22, 2013)

Thanks. The whole reason for this topic is about my daughter's car. She bought a used 2006 Corolla from a dealer, along with some free oil changes. They used a synthetic blend oil, and they told her she couldn't go back to conventional oil. The free oil changes are used up, and she was asking me about this. 

It sounds like the dealer lied to her. What a shock !!


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## noquacks (Jun 5, 2010)

Jim McC said:


> Thanks. The whole reason for this topic is about my daughter's car. She bought a used 2006 Corolla from a dealer, along with some free oil changes. They used a synthetic blend oil, and they told her she couldn't go back to conventional oil. The free oil changes are used up, and she was asking me about this.
> 
> It sounds like the dealer lied to her. What a shock !!


So much "professional mechanic" bunk out there, especially when trying to impress a woman (assuming of course that the mech was a guy....)


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## CharonThePunk (Apr 22, 2016)

I'm not an expert but I thought I'd chime in since I asked a question on another part of the forum and I feel bad getting info without at least trying to give some back! I've been changing my own oil for a while now (as a woman, it's been helpful to familiarize myself with the bare minimum of car maintenance). I've successfully switched between synthetic and conventional, but WindowsOnWash is right...there are hucksters that try to sell you synthetic but are actually selling you. Here's an excerpt from an article about making sure to use full synthetic oil:

"If you do opt for the synthetic option, be sure it is full synthetic. Some companies offer oil that is a blend of conventional and synthetic."

Probably preaching to the choir here but I hope it helps someone! Nice to meet you all! 

–Charon


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## motoriderx7x (Oct 16, 2014)

Somewhat off topic but...You could always get the proof for which oil is best for your engine specifically:
I do oil analysis on all my vehicles usually once a year unless it's a "new to me" vehicle then I get one done each oil change for the first 3. It only cost 30 bucks and I have the results in a week or two. It helped me determine that Rotella t6 was best for my Cummins and that I could do an oil change every 8500 miles despite the oil change warning in my truck. I've also done analysis on my bike when I was using the factory oil which was sheering before my normal interval of changes. 
http://www.blackstone-labs.com/ is what I use but there are others.


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## DC112 (Jun 20, 2016)

I just use the oil the manufacturer recommends. Most of my cars I used 5w30 synthetic oil because of the small engine size.


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## SPS-1 (Oct 21, 2008)

Jim McC said:


> It sounds like the dealer lied to her. What a shock !!


 Lets give him the benefit of the doubt. There is so much mis-information out there. Could be he actually believes this because "a guy told him", or because he "read it on the internet". Or he once knew a guy who switched from synthetic to conventional and the next day his engine blew up - so that proves you can't do it. For that matter, was this the chief mechanic at the dealership or a "service advisor"? Bet if you asked him how he came to that conclusion, he wouldn't have a good answer. 

I always use Mobil 1 full synthetic myself. That was manufacturer's recommended oil on the car I bought back in the day. Sold that car last year, but still use the Mobil 1 -- its habit now.


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## ukrkoz (Dec 31, 2010)

Speaking of "rule of thumb".
And, btw, other poster was right - if you have leaks or blow by burn out, do NOT use synthetic.

So, rule of thumb is simple - if your car takes oil in any manner - do not go synthetic as it is waste of money. Synthetic oil is more "liquidy", has higher flow ration than conventional oil. It will leak out or burn out much faster. Which for say Amsoil types costs a lot of zoo zoo to lose all that oil.
As of "washing debris"... Maybe. I pre-wash engine with Seafoam in oil for several hundred miles before oil change, so it's not an issue to me. Engine is clean and ready.
Lubrication is much better and it lasts longer for sure. But you need to have a very tight engine. Old loose clunkers or GM engines with huge tolerances - I'd stay away from synthetic. Do good conventional. 
I used to do oil changes every three weeks by 3 000 miles rule back in time. I was driving 11-1200 miles a week then. I learned a lot about oils as I got fed up with this. That's when I discovered Royal Purple, then Amsoil. But if it's oil taker - no reason.
You can switch, mix and blend all you want to. It's oil.


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## YerDugliness (Jun 2, 2008)

I have a different experience. I bought a brand new 2002 Mitsubishi Eclipse for my daughter's high school graduation present. She is a driver, not a mechanic, so I had her let me do all the oil changes. I had heard that it was not a good idea to switch to synthetic oil right off the bat, so I waited until I had a couple of oil changes on it and then made the switch.

Immediately the car started using huge quantities of oil and smoked like a mosquito truck. The dealer would do nothing to help…at that time "they" were not recommending full synthetic oils and they said I had voided my warranty. I kept pointing out that the oil met the ANSI (???) standards required by Mitsubishi, but I guess they were deaf…or dumb…or just both.

It was a beautiful 25th anniversary special…my daughter sold it for $1300 at the first opportunity.

I always thought there must have been some sort of factory defect.

BTW…that Mitsubishi dealership no longer exists…wonder why? I know I left the building after the discussion with the shop foreman, angry and vowing that I would never go back. There must have been others who felt the same way.

Dugly


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## jlhaslip (Dec 31, 2009)

Synthetic is nice to have when it gets terribly wintery out.
At minus 40 C, I am glad to be using it.
For the Spring/summer/fall oil change, I use regular stuff.


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