5-20 Synthetic Oil Creates Clattering Sound

Q: I put a new brand of 5-20 synthetic oil into my Hyundai. Oil light came on.
Clattering sound commenced. Drained oil. Put in normal oil. Oil light went out.
Clattering sound stopped.

Q: Does anybody. (factually) know why?

It’s not likely the oil is the problem. How many miles on the car and what weight of oil is “normal”? It could be that the engine is getting tired and if the “normal” oil is heavier that could be shutting things up due to increased oil pressure which can also open the oil pressure light switch and turn it off.

What new “brand” did you put in? Is it API and SAE approved?
Were you using synthetic before? Same weight? 5W20?
How many miles does the car have on it?

Synthetic should make absolutely no difference. Synthetic and dino (organic) oil are chemically exactly the same. Synthetic only has fewer impurities and the molecules are allegedly more consistent in size. Since they contain fewer inpurities, they stand up to heat better, and the more consistent molecule size along with the fewer impurities makes them less susceptible to severe cold weather problems.

But what CAN make a difference is buying off-brand oil at flea markets and yard sales. Often these will not meet API or SAE requirements, and they may even be old, not up to current oil specs. Oil specs do change over time.

The only way to factually determine exactly what happened would be with an analysis of the oil… or by reading the bottle and finding out that it doesn’t meet spec.

By the way, kudos for being alert and doing the right thing.

Did this event occur as part of an oil & filter change? If so, on start-up, did the oil pressure light go off after a few seconds? Since the filter is dry, it sometimes takes a few seconds to fill the new filter and build oil pressure. Until then, you can expect some engine noise…

How long did you let the oil drain the first time before you poured in the 5W-20? Sometimes, with prolonged drain time, the oil pump takes a few seconds to pick up the oil after it has been replaced.
I remember one of the old “Tales from the Model Garage” where the oil pressure light wouldn’t go off when one of the proprietor Gus Wilson’s customers had his oil changed at a filling station down the street. Gus just raised the front of the car with a floor jack and had the customer start the engine. In a few seconds, all was well.
I’ve had this problem myself and am always a little nervous when I first start the car after an oil change. One trick I learned was to fill the new oil filter with oil before installing it. This reduces the time it takes the oil pressure to rise.
I would bet that when you drained the 5W-20 oil and replaced it with “normal” oil, you didn’t change the filter. The filter was then already filled with oil. I’m sure everything is o.k. except for the cost of the oil you immediately drained out. I hope you saved it for future use.
I think @Caddyman is right on target with his explanation.

Normal oil? And just who decides what is and isn’t normal?

“Normal oil? And just who decides what is and isn’t normal?”
@PvtPublic–Carl Friedrich Gauss is the decision maker of what is and is not normal. Gauss derived the function for the statistical distribution which is known as the “normal” distribution. This normal distribution is sometimes called the Gaussian distribution by mathematicians who are more formal. Maybe we should refer to this as Gaussian oil to add to the confusion.

Unfortunately, Gauss has been dead for a long time, so he probably never made a decision as to what is “normal” oil.

Cute. But I’m fairly certain by the context that he meant dead dinosaurs.

By the way, I agree with the comments made by others that the clattering might have been because of the filter needing to fill up. It’s common. I’m a bit embarrassed that I didn’t think of it myself.

“…he meant dead dinosaurs.”

I know we all use this description, but to any new readers, almost all petroleum originated as dead plankton and algae that settled to the bottom of the seas eons ago. I have not been able, however, to find definitively that an aquatic dinosaur might not somewhere be part of the mix.

LOL, you made a good point insightful. But dinos were carbon-based life forms too, and as such they qualify to contribute to the mix. And perhaps a few wooly mammoths and cavemen too. The only reason that plankton and algae (and plants too… don’t forget plants) were the biggest contributor is that they were far, far, far more significant in volume than all the vertebrates on earth.

And then there’s the “age thing”. Algae and plankton were on the earth for some 4 billion years before vertebrates arrived. Lots of time to store up a cache of ingredients for oil before vertebrates arrived.

I still like the term “dead dinosaurs”. Sort of gives oil some character. Makes me think of Earl Snead Sinclair.