The biggest differences come from additives, storage, and station maintenance.

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Here’s what actually varies:

1) Detergent additives (the biggest factor)

Most name-brand stations (Shell, Chevron, Costco, etc.) use higher levels of detergent additives — often labeled Top Tier?. These help keep injectors, intake valves, and combustion chambers cleaner.

Non-Top-Tier stations typically meet only the legal minimum. Over time, that can lead to:

• rough idle

• loss of power

• worse fuel economy

• carbon buildup

2) Station storage maintenance

Old or poorly maintained tanks can contaminate fuel with:

• water

• rust/sediment

• microbial growth (yes — it happens in diesel especially)

Two stations selling the same supplier’s fuel may perform very differently depending on how clean their tanks and filters are.

3) Fuel turnover rate

Busy stations usually have fresher gas. Small, quiet, cheap stations may have fuel sitting longer — especially premium — which can break down and absorb moisture.

4) Octane consistency

Octane (87/89/91 or 93) must legally match the pump label, but at low-quality stations:

• blends may be sloppy

• pumps may not be calibrated well

You might feel knocking/pinging in sensitive engines.

5) Seasonal and regional blends

Gas is formulated differently in winter vs. summer, and state regulations vary. Some areas require more evaporative control, which can slightly change feel and mileage.