Was more referring to local refineries more than stations - although stations are important too - especially when it comes to water. There is a refinery here in Baton Rouge that ALL the local gas and diesel comes from. It's an Exxon refinery that dates back to before WWII. No matter what brand fuel or what station you buy from around here, it came out of that refinery. Probably 90+% of the roughly 30,000 gallons of diesel I've pumped into this truck came from there. My brother, on the other hand, lived in Phoenix and Houston for most of the first ~130k miles (first set of injectors) on his truck. Obviously different oil refineries making the fuel he was buying.
This is about the only real differences I can call out between his truck and mine yet he seems to get ~130k / set of injectors where I get 80k / set. There is also the fact that I towed a good bit more with my truck than he did with his but not sure how much that comes into play either.
Regardless, there is a large range of mileage that people see on LB7s for injector life. A lot of the ones I've seen claim 200k+ miles on factory injectors were completely stock trucks still running factory filter setups with OEM filters.
What causes the huge disparity? I'm not sure but as far as I can tell, it's not Air Dogs and such. I've never seen anyone who could prove that they got 10 additional miles on a set of injectors after installing an Air Dog or what-ever filter system.
What I do know is that the SAC type injectors should pretty much solve the problem.
2002 Chevy 2500HD Crew - Original owner - 407,000 miles so far. All stock with the exception of a lift pump and Donaldson filter