Half black half white spark plugs on each cylinder, spark 2007

Hi guys,

This is my first post here. Thanks in advance for sharing your knowledge and expertise. I really appreciate it.

I don’t have so much expertise in car mechanics but I do a bit of work on motorcycles (hobby).
Either way, I have just bought a 2007 spark for my girlfriend. It seemed an OK buy at first, engine sounds fine, fairly low milage (60 000; presuming it’s not tampered with), healthy looking exhaust etc.

I started doing some maintenance and started seeing one thing after another. First, there was water rather than coolant in the radiator reservoir. The owner is a mechanic, so this worries me. We just drained that today and added coolant, but I fear that we’re going to experience wasting of the liquids due to whatever underlying cause.

Next we changed the oil, AC and fuel filters. Took the spark plugs out to get an impression of the combustion efficiency. Unfortuantely I was presented with very strange “half half”-looking spark plugs, where one side (of the very same ignition site) was white (very lean) and one side black (oil? Carbon?). Sadly I didn’t take a picture. All of the spark plugs looked the same; half and half. The mechanic suggested it could be burned exhaust valves, but seeing as they all look the same, I don’t think it is so likely. I read online that it could be a timing problem. This worries me, especially as it sounds more likely. The car isn’t misfiring but it seems to lack a lot of performance (granted, it is just a 4x1000cc engine after all, but it feels dull, and I also feel that it is consuming more gas than it should). I also read it could be a gas pump problem, but I don’t see how that would cause the half and half appearance that I am presented with here.

At this point I am starting to fear that I might have bought a rotting car. There was some oil in the breather hose (didn’t look terrible) and a very slight oil leak from the front part of the gasket in the oil pan (sorry if this isn’t the correct term). No oil in the coolant (well, water….), no black or ugly exhaust. Engine sounds fine to me, but I am not an expert.

I would be very very grateful if anyone has seen this strange spark plug appearance before and tell me what it could be.