Thanks for the posts and sorry I missed them till now. Good tip keeping the full tank-makes sense that nothing can set there in the open pocket and fester.

 

A full tank doesn't matter like it use to. Now with sealed gas caps, and poly gas tanks. You just don't have the same issues. Gasoline can last up to two years or as little as 3 months. A lot has to do with how it is stored. When you get gas at the pump you don't really know how old that gas is. It could have been refined six months a go. I can write the whole chemistry on how gasoline degrades if someone wants to know.
The first thing that happens is. The lighter fractions (such as pentane, iso-butane, toluene, etc) gradually evaporate off, which makes the resulting fuel blend harder to vaporize in the engine and ignite. Along with that the fuel oxidizes. This it when it gets darker and leaves a varnish. It also can erode certain parts. This from The anti-gumming additives being consumed over time, causing sedimentation as complex molecules slowly inter-react into heavier molecules. This is exacerbated by loss of lighter fractions, because they tend to be strong solvents and help keep contaminants dissolved. Going on along with all of this is Microbial digestion. (Yes, gasoline is somewhat biodegradable to specially-adapted organisms.). Storage, how long it sat in storage before you bought it, how you store it all plays a role it how long it takes to " go bad". Then you also have winter and summer formulations. This causes issues too if using one in the wrong season.

 

That's why its always a good idea to buy name brand gas at a newer, busy gas station.

1. Quality of the product is better, and for 87 grade, Shell is the same price in my neck of the woods as no-name gas next door.

2. Newer gas station is going to have plastic underground storage tanks that don't leak. Older gas stations have metal tanks that let groundwater in, contaminating the gas. The newer tanks aren't going to have 30 years of crud accumulating on the bottom of their tank either. Plus things like filters are changed more often in newer, nicer stations.

3. Busy gas station is constantly having the tanker truck come by every few days to fill up the tanks, doubt you are going to get old/bad gas from them.

 

True , but you never know how long it sat at the refinery. You don't know how long it has sat in a holding tank or tanks for the distribution companies. So there is always that unknown.

 

True that, but buying gas from a non-janky, newer, busy station will eliminate that variable of your gas getting contaminated there.

 

Appreciate the great info Coleroad and Aron9000. Does it help to know that I use only Chevron gas and no other? Also though not required I stick with 91. I probably wouldn't see a notable difference but it eases my mind knowing that the motor isn't having to retard its timing to compensate for lower octane occasional knock.