I am about to change my spark plugs from NGK TR6's to Bosch Platinum plugs. The NGK's are pretty old and need to be replaced. My problem is, I hate changing the plugs and I might not finish this in one day (I have other stuff to do) so would there be a problem running the 2 different plugs for a few days until I complete the swap? Thanks.

 

I did that on a different car I had. It was a v6 and it had 3 ngk on one side and 3 bosch on the other side. Ran fine for like a year.

 

I agree no problem. You should be able to run a different brand plug in each cylinder for years, But I don't know why. I know guys with old high milage cars that have a cylinder that has worn rings/valve guides that will run a hotter plug in that cylinder. I knew one guy that claimed he got a plug for a two stroke lawn mower to fit in his real old car that was using oil. The two stoke plugs are hotter and are less prone to oil fouling.