Oil and gas industry: which degree values more when it comes to working in the oil industry, a Bs in Mech or a Bs in Petroleum engineering?

Doesn't matter.  What makes the biggest difference is the school you go to.  Not because of the quality of education, but the industry contacts and exposure that comes with going to a target school (A&M, UT, TT, LSU, Mines, etc...), although I have been told by some industry engineers that they would rather hire an ME over a PE because the education and skill set is broader.  I can see why in some cases, but there is still huge value in a PE undergrad.  I am ME and was offered both onshore and offshore jobs.  I feel like my ME education has greatly benefited me because I deal with a lot of metallurgy and failure analysis, and as an ME I have a solid fluid mechanics and thermodynamics background.  As long as you understand the basics you learn the rest on the job.  Most oil companies have a structured 2-3 year training program for their new grads.  I work with ME, Chem E, and Civil E guys who are now petroleum engineers.  Oil and gas companies value experience over education a lot of the time (up to a point).

Since you're anon, I can't tell where you live, but with a mechanical engineering degree, I believe you'd be more likely to work in an onshore oil industry job. So if going offshore is important for you, petroleum engineering might be a better fit. In today's boom-time for oil and gas, they are recruiting everywhere. Electricians are being hired and re-trained to construct and assemble the electrical parts of subsea installations being built onshore, so who gets in right now isn't necessarily a good indicator of job security for the next 10-20 years

Yes, I have seen many excellent petroleum engineers with different educational backgrounds (petroleum engineering, mechanical engineering, chemical engineering and even civil engineering). But to be quite candid, if you know you want to work as an engineer in the oil industry, the best choice is to major in Petroleum Engineering. Why? 1. The education is much more relevant, you can hit the ground running on day one vs. having to be the kid asking ridiculous questions and relying on the company training program. 2. In case you haven't noticed the difference in starting salaries, most oil companies base your starting salary off your major and NOT your job title. Take two kids fresh out of college both working as "Petroleum Engineers". The kid with a PE degree will be paid $100k while the kid with a MechE degree will be paid $70k.

i think it odd that many people dont have relevant education in oil industry work in this industry, then many people of relevant education - petroleum engineer, ship welding etc. have decent income, but those who become big are not educated with petroleum courses, but irrelevant courses in top rated universities - they become management ;-p