Motor Knocks

Hey guys, I'm about to buy a 2002 4runner Sport from a friend of mine and he's had it since it had 10k miles on it, it currently has 160k. He's taken extremely good care of it which is why I'm interested in buying it. The only problem he says, is that the motor has a "knock" when he uses 87 octane gasoline but not when you use 89 or higher. I've never heard that before and I've had a couple of Tacoma's that have had the 3.4L and never have I had an issue with a knock! I know he's not trying to hustle me or anything, and he's not the most mechanically knowledgeable person out there. Maybe a knock to him is a tick to me. I don't know. Either way, assuming it's a knock, has anyone ever had experience with this and/or heard of this. It's obviously not required from Toyota to run 89 so I'm confused. I don't see him that often so if I could on a whim I'd drive to his house and test drive it.

 

My 2011 with 27k on it has a light tick, which I was told on here is just the spark plugs and was commonly referred to as the "tacoma tick". A knock, however, sounds more concerning

 

Yeah that's what I was thinking. He was telling me however how he changed the spark plugs and wires. I don't know what to expect. Like I said a knock to him might be a tick to you and I. I haven't heard the car run in quite a while.

 

Anybody else?

 

it would help if you can get a video clip of it knocking.