I am fairly mechanically inclined, I do all the maintenance and repairs on my cars. I have encountered an issue that has perplexed me and was looking for more insight.

I am getting a rotten egg smell. As I have always understood it, the rotten egg smell is the result of the sulfur in the fuel contacting the platinum in the catalytic converter.

I am going to withhold a few vehicle specifics, for now, because I have been getting some automatic generic responses that the catalytic is bad and needs to be replaced. I do not buy that, however, if this continues I believe on a long enough time line it will eventually ruin the catalytic. In this case if I were to replace the catalytic, I do not feel the problem would be resolved and would still continue.

I will say that if I change who I buy the fuel from it seems to stop temporarily. It seems to resolve it for 3-4 tanks of gas then it returns. I have three different places that I cycle through buying gas from.

What could be some other things that could cause this to happen? I will say that I am forced to use premium fuel.

Sorry for the lack of vehicle information and vagueness, this is just how my bullshit detectors work.