Toyota Repair: oil use, engine gaskets, rav 4

Question
QUESTION: I have a 2009 Rav 4 with 35K miles. I always used conventional oil with each oil cahnge.Is it beneficial to change to synthetic oil or will conventional oil suffice?

ANSWER: Use the oil the manufaturer recommends, it's stated on the oil cap, I believe for this engine it's 5W-20, change oil and filter every 5000 miles, synthetic is more expensive but you can wait longer for oil changes, every 7000 miles.

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QUESTION: Is the synthetic oil conclusively proven to significantly reduce cylinder,piston,bearing and ring wear as opposed to coventional oil? Is the alleged one mile per gallon greater synthetic gas mileage worth the 100% greater cost? Please advise.Would changing to synthetic after 35K miles harm engine gaskets and seals? Thanks.

Answer
The answers to those questions are: the makers of the synthetic oil make claims, I can't prove or disprove you have to do some research and decide yourself
Don't have any information on gas mileage improvement, another claim by the oil companies
No it would not harm the engine to switch to synthetic oil.
Keep in mind the "your results may differ" disclaimer.