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I have a 2017 Elantra (nine months old). At my first oil change, the dealership (without my knowledge or CONSENT) out in semi-synthetic oil (which is NOT required or necessarily recommended by the owner's manual.)

I want to change BACK to regular oil, but I understand that I must flush the engine first.

Should I flush it? Is it safe?

  • That vehicle does not call for Conventional Oil. It most certainly calls for Semi-Synthetic at a minimum, but Full Synthetic should be run. – NitrusInc Apr 10 '18 at 18:14
  • I believe you (& thank you for your answer) BUT, I looked in the owner's manual & did not see anywhere that it "recommend" synthetic or semi-synthetic oil. – Jersey Joe Apr 10 '18 at 19:05
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    no need to flush the engine, a waste of money and time. – Moab Apr 10 '18 at 19:18
  • @JerseyJoe Thank you, and thank you for your patience. What certification(s) does it list? That is all that matters. If the oil you want to use meets those or "exceeds" those specs. You're golden. You don't need to flush. Just perform an oil and filter change as normal. – NitrusInc Apr 10 '18 at 19:23
  • This could just be an Advertising Agreement... But this might be intersting to you. Hyundai specifically selected Shell as their perferred Aftermarket Oil Supplier: shell.com/business-customers/lubricants-for-business/… Run some Rotella in it if it meets specs! – NitrusInc Apr 10 '18 at 19:25
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Regular oil as in dino oil? I wouldn't bother. Synthetic oils are usually considered better than dino oil. Many cars don't require synthetic oil, but using a better oil than recommended usually won't lead to problems.

Flushing the engine is unnecessary. If you want to change all of the oil, just drain the old oil out and put new oil back in. Some small amount of the old oil might stay there and if the oils are substantially different they will not always fully mix. This isn't a problem or else we would have a major number of cars suffering from problems where somebody topped oil with a different type of oil due to oil consumption.

The dealership usually know what they do. In this case, they used oil that will not damage your car engine.

  • Thank you for the info. 👍🏻🙂. While I realize that a "better" oil wont cause damage to my engine, i wanted to switch back to regular oil BECAUSE its so much more co$tly every time i get an oil change. > My concern however, is that switching back (at my next oil change) "without" flushing 1st, may cause engine damage. ((its a new car so i dont want to damage the engine & void the warranty)). ... & NOW, I was told by someone else that flushing the engine could cause problems. So, i really dont know what to do ?? – Jersey Joe Apr 10 '18 at 19:12
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    @JerseyJoe If you feel the need to flush it, which you don't need to, simply do an oil change as you would plan to... And then do a second one after say 100 miles. I wouldn't run anything else through it to flush. – NitrusInc Apr 10 '18 at 19:18
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    Something to add to the answer here is semi-synthetic oil is partially synthetic, partially dino oil. Every time the oil is changed with the stuff, you have a mixture of oils (compatible oils, no doubt). Changing to a dino oil at that point would be akin to changing it with pure synthetic. There is ABSOLUTELY no need to flush the engine, whether you're going from dino to synthetic, the other way, or anything in between. Just isn't needed. Keeping maintenance up in the car is far more important. – Pᴀᴜʟsᴛᴇʀ2 Apr 10 '18 at 19:55
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    @JerseyJoe: Synthetic changes are more costly, but they also last a lot longer (in practice, full synthetic is supposed to last 2-4x longer than conventional oil). Sure, the full synthetic stuff costs more per change. But if you're performing half as many oil changes (or fewer), the premium is worth it. If it lasts even twice as long (the low end estimate) and a regular change cost you $30, paying $60 for full synthetic is worth it. And that's before we get into the value of your time; if you waste 1-2 hours of your time on each change, halving the waste is worth something too. – ShadowRanger Apr 11 '18 at 0:51
  • @ShadowRanger: Who needs 2 hours for an oil-change? – Daniel Apr 11 '18 at 9:25
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(Expanding on other answers, but this won't nicely fit in a comment:)

It's worth noting that many manufacturers - Nissan comes to mind, I think Honda as well - specifically say to never perform an "engine flush." There are a number of documented cases of these flushes causing engine failure.

On higher mileage motors, the flush can loosen up debris which can then block oil passages, gum up the oil pump, etc. (My G35 threw a rod less than a thousand miles after having it flushed. I read about all the caveats a little too late.) On a 2017 model - I'm assuming relatively low mileage - I doubt that would be an issue, but on a low-mileage engine it also wouldn't be necessary.

To reiterate: if the manufacturer says semi-synthetic, do it, or full synthetic. There's no reason to go with 100% dino oil other than to save $100/year on oil changes. Considering you just paid for a brand new car, it seems silly to shorten its life for such a small price difference.

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