Effect of Burning Oil on a Spark Plug

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I switched over my 16.5 Hp riding mower (2004 B&S Motor) from conventional oil (10W30) to synthetic (Pennzoil 10W30) this year. I noticed that it started burning about 1 oz of oil per hour this year (it never did before with the conventional 10W30). Some people have told me this is normal when one switches to synthetic and that it should stop burning oil in time. After about 20 hrs use, it is still burning oil.

This weekend I took out the spark plug (it was put in new at the beginning of this season) and it was all crudded up with dry black gunk on the electrodes and insulator material and in between the insulator and the round electrode that surrounds it. This material is dry and one can sort of chip it off if pressure is applied. The plug I took out from the year before was fine, a nice tan color electrode and fairly white insulator.

My question is whether the burning of oil would do this to a spark plug or would I have perhaps another condition that I should look into? Apart from gunking up my spark plug the mower seems to run fine and has 105psi of compression.
 
The oil cause the deposits on your spark plug. if you were having a mechanical issue the sparkplug would have at a minimum silver deposits and could also be bent or broken.

replace the plug.
 
I used to have a Bolens with a 12hp OHB Tecumseh (not original). It would burn about 1/2 quart of SAE50 in 45 minutes running time. I used a Lawn Boy plug and could get about 12 mowings before it would foul.
 
Originally Posted By: Brett Miller
I used to have a Bolens with a 12hp OHB Tecumseh (not original). It would burn about 1/2 quart of SAE50 in 45 minutes running time. I used a Lawn Boy plug and could get about 12 mowings before it would foul.


Wow! That's some serious consumption for a mower engine!
shocked2.gif
 
You got it. Didn't have to worry about bugs when I mowed. The strange thing was, it ran well and had plenty of power. Then one day, my wife was mowing and all of the wiring burnt up. Replaced with a new JD.
 
Originally Posted By: Brett Miller
You got it. Didn't have to worry about bugs when I mowed. The strange thing was, it ran well and had plenty of power. Then one day, my wife was mowing and all of the wiring burnt up. Replaced with a new JD.

Thats why i dont let my wife touch my mower...knowing her luck something will get fried.
 
I was acutally ecstatic...........I could then get a new JD. That Bolens was like driving a tank. I put the Bolens in the classifieds for free and it was gone the first day.
 
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