I have heard
that cars using RP tend to be consumed at a slightly higher amount than typical oils. I do not know how accurate this is.
There are some that will argue a moly-based lube should not be run in a street driven type of vehicle due to long-term damage. RP is one of the only oils using Molybdnum disulfide which is formed from a solid metal. Moly is a refractory metal capable of withstanding high heat, and in powder form is a great lubricant. That's basically what your oil is...this is liquid form
I'm not a petroleum engineer so I am not going to say to not use it here. Plenty of people use it fine. So don't jump down my neck if your friend Jim-Bob has put RP in his car for 250K miles without issue. Good for them. I don't work in the industry so I haven't tested it so i am nowhere qualified to say it's no good to use. I work with moly in a solid state a lot and it's very gummy, but slick. I have a bar of it on my desk right now and it's almost like a greasy piece of lead (expensive too..that's why the oil costs so much). I
personally would not use it in my own street car. I'd run Amsoil/Mobil 1/Castrol first. Most people i know using it use it in specialty race drag cars, where the motor is torn down every 5K miles and new bearings and rings and such are installed.
But 2.5 quarts in 6K miles may not make the cut on an OC test. I routinely do my own OC test on my 5AT car and find i consume about 1.25 quarts per 3500 miles. However, it's consistent, and according to the chart on the OC TSB, would not get me a new engine and is considered "normal"...however it's excessive for any car i've ever owned.
Since i change my oil so frequently, it's the main reason I don't run synthetic. I drain and measure my oil every 3000-3500 miles.
Since he's at 60K, he may not be under warranty any more.