How much gasoline fuel to keep in tank of low use vehicle

Question

For a low use vehicle, it was historically recommended to keep the gas tank full. The reasons were twofold:

1. Prevent rust from forming in the metal gas tank
2. Prevent water from forming in the gas tank due to evaporation and condensation

Nowadays, I wonder if either of those two rationales apply.

Are there any mainstream production vehicles that still use metal gas tanks? If not #1 is moot.

Given the advanced seals on current gas systems, is #2 still a factor? If so, why?

Overall, for a low use vehicle, I wonder if it is now advisable to keep the gas tank at 1/4 a tank or less. When I say "low use", I'm thinking of a vehicle that is driven 2-4 times per month for a total of about 100 miles per month. That way, when it is driven, and a little fuel is added, more of the older gasoline is replaced.

If a vehicle is driven 2-4 times per month for a total of about 100 miles per month, I don't think fuel additives are necessary.

For a low use vehicle (as defined above), in order to keep it healthy, how much gasoline should be kept in the tank?

Answer 1

Another concern of leaving gasoline in a fuel tank is that it degrades. If left long enough, it will not burn as efficiently (if at all) and will cause many internal issues.

Gasoline in a fuel tank should be good for a minimum of six months before you need to start worrying about anything. Given you are driving the car 2-4 times a month for about 100 miles, you don't need to do anything special to keep anything in the car in good condition besides the typical maintenance (oil change, etc.).

You should be able to fill the gas tank to the top and just fill it up when needed without any treatments.

Check out this link for more information about low-use vehicles.