If my sparkplugs look like this (see picture), is it possible to tell if the o2 sensor is ok?

 

The plugs looks pretty darn good actually. Just looking at the O2 sensor will tell you nothing, the easiest way to check it would be to hook a scan tool (not a code reader) and watch the data stream. The O2 should switch between .01 (lean) volts to .9 volts (rich) rapidly. If the voltage does not change or is sluggish it means the sensor is failing.

 

But, if the O2 sensor is bad, it would be to rich or to lean? and that would have impact on the sparksplug? I dont have any scantool, but i could use a normal analog voltmeter and measure the O2 sensor, but if the plug tells that the fuel/air ratio is good then i dont use any time on change it. I have a Bosch O2 sensor to use, but i have read that i shouldnt use the Bosch O2 sensor in this engines? so if it looks ok i'm happy :-) but it still only get 12-13MPG. If one of the injectors where leaking/open, that should have been showing on the sparkplug? All 6 is looking the same.