piston slap/different oil mixture

To get rid of what appears to be piston slap, I put in 4qts mobil 1 10/30 synth, and 2 qts mobil 1 15/50 synth. I cant seem to get a hold of 10/40, so this is what I came up with. Got rid of the K&N air filter as well. It def quieted it down, and it runs a lot smoother. Any probs doing this on a regular basis, and keep on doing this for the winter? What would be my final weights after this synthetic mixture?

2000 XJ
132K

regards

JH

Mixing weights won't give you a true intermediate result. No harm done, but you might be better off getting the correct viscosity.

Mobil makes a 0w40 M1 that's fairly common. That might work for you. Seems like that's getting more common a choice for the 4.0. Mobil 1 also has a 5w40 Truck and SUV oil also.

Castrol still makes their Syntec 5w50. Amsoil has a 5w40 too.

--Matt