Yep, this vid by Donalds has me convinced the root cause of TimingGuides breaking
is these OilPressurized TimingTensioners get internally gummed up with oil sludge,
not so much the internal spring wearing out.
He's really cool and helped me via PM when I had threading issues with my front tensioner a while back. Loves to tinker and he told me he services vintage guitar amps on the side. Wonder if he ever figured out at 3:43 what that "little spot for oil to drain past" is for? Doesn't make sense to me either. Maybe I'll PM him again. LOL
For reducing oil sludge I use AvBlend in my STA engine. I'm an airplane mechanic and I have discovered this additive will clean your engine. I've cured sticky airplane engine valves with AvBlend. I buy it by from Aircraft Spruce @ ~ $15/bottle. Or you can spend $40 for a two bottle pack of Z-Max down at the auto parts store. The only difference between the two is the dye. It's hard to find the single bottle (flask) any more. Advance Auto Parts is about the only place and it's $27/bottle. I've heard that Marvel Mystery Oil will do the same thing, but I haven't used it. I do know that my airplane engine oil analysis improved with every oil sample when I started using AvBlend. So I'm sticking with it.
I'm not an oil expert by any means, but many of the tweaks on the BITOG forum are. Talk about deep. Most there seem to agree that additves used in today's premium engine oils are sufficient. In fact, adding anything to oil is usually frowned upon. I've always believed that since I began using Amsoil synthetics in the seventies. YMMV. What's surprising is how often AIR FILTERS are overlooked. Contaminants in used oil are getting past the air filter. Not sure about aircraft engines, but most outboard engines don't have air filters.
Not every tensioner fails, I've compared my original ones and new ones, rear one on mine was weak. Front one was fine, probably why the front guide was in impeccable shape, and the rear guide was broke. They have to keep preload on the guides so they tension the chain and keep chain slap to a minimum.