Synthetic in winter, dino in summer.......safe?

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Can you switch between synthetic & dino without any problems in the long run? Some people say it is a myth that synthetic will cause seals to leak others say that their vehicles personally leaked after switching to synthetic from dino. What are the straight facts on this seal issue?

Planning on using dino in the summer & synthetic in the winter.
 
In your case there should be nooo issues with the switching.
For very, very old engines that have hard, old material, seals that maybe even weep a bit with the old oil but are supported by deposits around the seals.
Such an engine may start leaking more due to the fact that synthetics clean some deposits from the seal areas and also flow better through minor gaps. They don't kill seals, they expose bad seals where old dino deposits have acted as high mileage oil.
If your engine is like this, the issue is not syn vs. dino, its regular oil vs. high mileage stuff.
 
It's not supposed to, but sometimes switching to synthetic will cause weeping out of seals.
I've seen it in the shop a number of times.
This does not happen as much lately. A few years ago it was more common.
But this would not influence me on my personal cars. It is NOT likely and is not a big deal.
 
Synthetics don't cause seal leaks, period. You can switch them out as you like, but why would you want to? Once you go to a synthetic why not use it all year?
 
I would just use the syn all year. During the summer you could extend the oil change interval to recoup the cost. By keeping the same type of oil you never need to wonder if whatever happens is caused by oil changing. To answer your question, I seen nor have I heard of any problems from switching in the last 5-10 years.
 
Various synthetic brands are on sale all the time. Stock up and buy once a year -- allowing you synthetic use year-round. Some synthetics sales are priced the equivalent to conventional oil. You can even start an oil stash like many of us here at BITOG. I presently have an approximate 30 month supply.... all purchased dirt-cheap. Go to the list of forums topics. Click on the last one at the bottom. That's where you find nice sales here.
 
No. It's not safe at all!
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Your best bet is to scrap that stockpile of synthetic oil.

I'd be willing to take it off your hands at no cost whatsoever. You can thank me later.
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XPR - But what about when they DO cause leaks?
I've had my shop for many years and can attest that it happens.
Someone will switch to a full synth motor oil, and they get leaks.
 
Depends on the type of Synthetic it seems. If its a good one like M1 or PP, they don't seem to do it. I can attest to it on 4 older cars. No leaks.

But also, if you've got some miles on your vehicle, what is the problem with just changing some gaskets?

As far as I've seen, most cars will start to weep a bit of oil at 100k+, synthetic or not, I think its just that people start to pay more attention to leakage once they've gotten the idea into their head that it will cause more leaks to happen.

I've made it a habit to change gaskets where common shrinkage happens, such as valve cover gaskets and grommets, the kit is maybe $20, and rather simple.

As far as switching in winter and summer, that makes absolutely no sense at all whatsoever. Synthetic is an advantage just as much, if not more, in the heat, as it is in the cold.

I personally suggest choosing a GOOD synthetic, such as M1 or PP, and to change any gaskets that are leaking. Also, be sure to keep a clean engine so that you can monitor any leakage that occurs.
 
Originally Posted By: mechtech2
XPR - But what about when they DO cause leaks?
I've had my shop for many years and can attest that it happens.
Someone will switch to a full synth motor oil, and they get leaks.


But they don't cause leaks. If it leaks after you change the oil, its not due to it being synthetic, there was something wrong before you added a synthetic oil. Synthetic oil causing seal leaks is a myth that just won't die.
 
"As far as switching in winter and summer, that makes absolutely no sense at all whatsoever. Synthetic is an advantage just as much, if not more, in the heat, as it is in the cold."

Actually in my climate it does. Tons of cold starts, idling, getting into the -30 Celsius weather in a few days here. My summers are mild compared to Florida summers. So yes I am getting more benefit with synthetic in winter.
 
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Your plan sounds good as I also wanted the benefits of SYN. in the colder weather, however, my Toyota owners manual addresses this exact detail and cautions AGAINST awitching between the 2 different types. When all else fails... read the instuctions.
 
Switching back and forth is not a problem and syn will not cause seals to leak but is a waste to flip flop. When you switch over, there's always some oil left from the previous change.

Think about it. When you do a switch from conv. to syn. normally the first syn. change will be shorter in duration than the second cycle and so on and so forth.

I change oil twice a year in my vehicles and stick with syn., usually use Amsoil XL.
 
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