Synthetic oil. Can it Really Go 10,000 miles?

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Yes.

In fact some synthetic oils can go far longer. AMSOIL Signature Series is guaranteed for 25,000 miles. Mobil 1 Annual Protection is guaranteed to go 20,000 miles. Mobil 1 Extended Performance is guaranteed for 15,000 mile oil changes.

Most synthetics however do not come with a mileage guarantee, instead they state to follow manufactures oil change recommendations. Having said that I would have no problem personally running any synthetic out to 10K.

Synthetic base stocks are more heavily refined and processed. This allows them to resist oxidation and thermal breakdown far better and last longer than conventional oils. You are correct that the additives wear out, whether conventional or synthetic. It does seem however that most synthetics have a more robust additive package than most conventional oils. A more robust ad pack combined with a higher quality base oil will allow the oil to last longer.

There is plenty of good info about oil at:

https://bobistheoilguy.com/forums/ub.../forum_summary

There is a whole section where you can read used oil analysis reports. There are many, many reports on synthetics run over 10K miles with plenty of life left in the oil.

Also the Petroleum Quality Institute of America has a website where they test fresh unused samples of oil.

http://pqiamerica.com/PCMO_Sample_Su...2_15_2016.html

You can tell the quality of the ad pack from these tests. You may be surprised to see some no name synthetics putting up numbers equivalent or better than name brand products.

FYI I currently have Walmart's house brand "Supertech" 5W-30 synthetic in my Yaris sump and I plan to keep it there for a year. I will not make 10K in that time but it wouldn't bother me if I did.

Read up and make your own decisions. Don't sue me if your engine blows up.

PS: Make sure to use a high quality oil filter like a Mobil-1 or Fram Ultra if you plan on running extended oil change intervals.