I buy the BG 44K in cases on Ebay for around $15-18/bottle and I run a can every few months. The dealer recommended I run it every tank but that's ridiculous. $20/tank... yeah right. Car runs great.

 

I must say that I hear this too... almost sounds like something is lose underhood. But it is less pronounced (still slightly present) with 100 Octane unleaded race gas. Dealer reflashed the ECU to the latest file and it made no difference whatsoever.

My vehicle is a 2010 XF Supercharged (5.0 AJ133 SC) 44K miles. There is no noise whatsoever in a 2011 XFR we drove back to back during the trouble shooting drive. Dealer's conclusion is to keep an eye on it to see if it gets worse and otherwise do nothing. That sounds like BS to me.

 

Different schools of thought on this I see..My dealer says to dump a can in every 5000 to 6000 miles on a full tank is more than enough and run it to almost empty, which I do and I also add about 6oz to every 10 gallons, Marvel Mystery Oil.....I buy cases too of BG44K and used it in all my cars for the past 10 years or so..One service tech once referred to it as, a shot of penicillin for the engine...