Dirty gas will cause your fuel system to plug up way before it gets anywhere near causing wear problems severe enough to require an engine rebuild. Maybe you've been hit with low-quality counterfeit parts that fail quickly? (That's assuming that the engine rebuilds have otherwise been done properly.)

If I had to deal with dirty gas, I would  use a filter before it hit the tank, and made sure to change the fuel filter often.

Have you been changing your fuel filter?

I will let others chime in on the rest.

Low octane fuel would mean the ignition timing would have to be significantly retarded so the engine wouldn't ping (detonate) and self destruct. 

Incase you forgot you asked this question on 11/27/21. There were answers for it. If you put  the topic in the search box you should find it. 

I have a 2005 Toyota Camry in Egypt, I rebuilt the engine five times and it only has 50,000 km on it, I am the original owner, I don’t rag on it, I am over 50 years old , is the dirty gas causing this ? I also have a 2005 Mitsubishi lancer 1.6 L since new, I had to rebuild the engine three times and the transmission once (transmission was rebuilt at 300 km), but I do know the cause of the transmission problem, it overheated while driving fast and broke the transmission chain because they put the wrong transmission fluid in it at the factory, there is no factory warranty whatsoever, I paid out of pocket to do all these repairs, the Mitsubishi has 55,000 km on it now. I also changed the fuel pump twice a year in both cars, and it looks like black mud is coming out of it, I clean the tank and put new fuel and the new pump only lasts 6 months, they lie and say it is 95 octane gas, A chemist told me that the octane rating at the pump is usually below 60 octane. Do you think the dirty low octane gas is causing these engines to go bad. I know the octane is low because when I turn off the car it stays running for a few seconds. I hope you answer my question.

Thanks.
Hisham

Yes