Briansue is correct, that Pemex is #4925. It is just past a large Monsanto chemical plant heading south. Here is my note from my Blog:
"We are in Los Mochis in back of Pemex #4925. There is a secure, fenced compound with a gate and 24 hour security. The guard checked us in, wrote down our plate number and had me fill in my name and address. There is no charge but we tipped him $50 pesos. We were the only RV this night and shared the lot with maybe ten trucks. There is a restaurant attached to the station where we had fish tacos for me and beef medallions for Norma."