I recommend you look into fixing it yourself if you are able. I understand you may not have the resources to fix your problem right now, but unfortunately there is no free lunch. As a DIY project, it will not be expensive.

If you care to keep the car for the long-term, then you should prioritize and fix the problem correctly when you are able to.

It is another story if your car is just temporary and you don't care about keeping it in perfect running order. If this is the case, throw whatever you want in there if you think it will fix the problem.

My mechanical opinion is that you may very well hurt the engine by putting an STP oil additive in. I think you are aware of this otherwise you would have not asked the question. If anyone could throw a bottle of magic into the engine and pronounce the problem resolved, there would be many mechanics unable to feed their families.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record