[demian5]

The gas in the oil could be bad rings. How old is the oil?
I'd do a leak down test before changing anything.

https://mobiloil.com/en/article/car-...-leakdown-test

And here is a guide for reading spark plugs yourself.

http://www.ngksparkplugs.com/about-n...d-a-spark-plug

Both of these responses are also great.

rotate the plugs to see if there is any difference , what type choke is on it ?

You need to change that oil cap out for a breather type cap.