Chain tensioner problems. - Toyota Kluger, 2.4 L, 2001

As I said, after the purchase, I did not change technical fluids (with the exception of antifreeze). The oil level was normal in color and composition, too, everything seems to be fine.
After 10 000 km still replaced maslo.Vzyal Shelovskoe 10 to 40.
It has been about 2500 km.Na low speed began to appear sound like dizelya.Snachala sinned on condensate glushake.V sound later became razdrazhat- and that the autopsy showed ...
Top the chain began to stretch: 15 links-3 mm (total links 200).
The whole block consists of two chains, two tensioners and two dampers. Since the oil (10/40) was too viscous for 2AZ, the channels of the tensioner simply did not pierce properly.
The 2 AZ engine uses oil, according to the SAE 5w20 classification. (Why did not know before ...)
I had to replace both chains and
oil. The repair kit came out at 12,000 r + oil 2500r + filter 300r.
The problem is solved.