I have always heard and read that 10w-40 oils were a bad idea b/c of viscosity index improvers being inherently unstable and that they left deposits and such in the engine. Now with modern 40wts (0w-40, 5w-40) this seems to not be the case anymore. I am wanting to run a 40wt synthetic or blend in my Nissan and Isuzu for protection and experimentation reasons. Now my question is: Would a synthetic 10w-40 such as Syntec or Syntec Blend be stable enough for say a 4-5k drain?
Thanks
Thanks