Synthetic oil

Tiny
PAPET
  • MEMBER
  • 2014 DODGE CARAVAN
  • 3.6L
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 45,000 MILES
So let's say I used synthetic oil for the first time and I want to switch back to the semi synthetic that I use before, are there any effect or will it affect the seals and gaskets? Thanks and hoping for your most appreciated reply.
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Wednesday, April 12th, 2017 AT 6:22 PM

7 Replies

Tiny
CARADIODOC
  • EXPERT
Please reply back to your original question. That is a private conversation between the two of us, but it also helps others who might be researching the topic.

I have had students switch to synthetic oil, then develop horrendous leaks within days. After a few weeks the switched back to regular oil. The leaks slowed down, but it took about two months and another oil change. Those leaks never did totally clear up on their own.

I cannot say those leaks were caused by the synthetic oil. For this type of problem we prefer to discuss changing brands of oil, not type. Every oil manufacturer has their own proprietary formulas for the additives they use. All must meet the latest specifications as outlined for the current "SC" and "CD" rating on the container, and that insures it is acceptable for use in any engine currently in production.

The problem is the detergent in one oil might be fine, but it will dissolve the seal conditioner in the old oil currently in your engine. When the oil is changed, about two quarts never drains out. It is stuck in passages and in the pump. What additives remain in that old oil could render another additive in the new oil ineffective. That is not an issue after another two or three oil changes, but where people run into trouble is when they use a different brand of oil at every oil change. When you stick with one brand, you know the anti-foaming agent will work with the seal conditioner and corrosion inhibitor, and with the other additives.

I have never used synthetic oil. I went fifteen years and over 150,000 miles without changing the oil in my 1988 Grand Caravan, as an experiment. I just added one quart every 1,000 miles, and that was enough to replenish the additives. The van finally rusted apart at 420,000 miles, and was running fine up to then. I doubt it would have lasted any longer with synthetic oil.
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Wednesday, April 12th, 2017 AT 8:00 PM
Tiny
PAPET
  • MEMBER
So if I switched back at once to semi synthetic oil, will it damaged the seals and gaskets? Thanks
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Wednesday, April 12th, 2017 AT 8:21 PM
Tiny
CARADIODOC
  • EXPERT
Again, it's not the type of oil. It's the different additives in those oils. Changing back and forth doesn't damage the seals. If it did, there would be all kinds of warnings to that effect. The different additives affect how flexible the seals remain, and how well they can do their job. If you develop a problem with leaks, then switch back to the oil you were using before. Regardless if you switch back to what you used before, or stay with what you're using now, stick with that brand if you aren't having a problem.
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Thursday, April 13th, 2017 AT 7:34 PM
Tiny
PAPET
  • MEMBER
Thanks a lot.
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Friday, April 14th, 2017 AT 6:21 AM
Tiny
HMAC300
  • EXPERT
Just for some help here semi synthetic oil is 1/4 synthetic 3/4 mineral oil.
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Friday, April 14th, 2017 AT 7:20 AM
Tiny
PAPET
  • MEMBER
Thank you
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Friday, April 14th, 2017 AT 7:23 AM
Tiny
KEN
  • ADMIN
Please use 2CarPros anytime, we are here to help and tell a friend.

Best, Ken
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Monday, April 17th, 2017 AT 3:33 PM

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