So, based on what you're saying, if I fill my tank and then drive so that it's only a quarter full (~2 gallons) and then don't anticipate needing more gas for several months, I should go refill the tank. This flies in the face of 10 years and a few million miles of experience with the only other PHEV that won't touch the gas if you don't need it. Remember, the tank is pressurized and the only way to get and keep a positive pressure in the tank is to pump air in as the gas is consumed.
My contention is that it doesn't matter if you start with a full tank and drive it nearly empty and let it sit there or if you simply don't fill the tank more than a couple of gallons when you know you're not going to be using gas. The air in the tank comes in from outside the tank in either case.
Also, since the Volt owners manual tells owners a lot more about the hybrid power train, here's the GM statement on how much gas to keep in the tank (took me a while to find the reference):
LOL,
There are Countless articles on the Dangers of running just a few gallons of gas in your tank as a normal practice.
https://www.google.com/search?q=run...XHilQKHYCMAiAQ_AUICSgA&biw=1366&bih=665&dpr=1
Rob43
A few posts back you told me to stop using anecdotal evidence, so I found and posted the citations from the owners manuals from both generations of the Volt. Now you're using third party sources for your evidence - you can't have it both ways.
In addition, if you fill the tank completely and then run it down to just a couple of gallons, the pressure has to come from pumping air into the tank. Fuel vapors simply aren't sufficient to provide the pressurization. So do you immediately go and refuel even if you're not going to be using gasoline for the next few months? The reality is the combination of small tanks, significantly lower engine susceptibility to water in the fuel, and positive tank pressurization makes PHEVs with small tanks very resilient when it comes to water vapor in the fuel tank combining with the Ethanol in the fuel. If modern gas engines had this as an issue then they would have water filters similar to those found in diesel fuel systems between the tank and the injectors.
As for OP's situation - he (assumption) posted that he's in the desert southwest. Humidity levels are so low there that water vapor in the tank is a non-issue, even if he were to screw up an put E85 into the tank. (He'd have a lot of other problems, but none related to water.)
I've downloaded the 2018 Clarity Owners Guide and Manual and read through both. Honda provides no clarity on this question, which is unfortunate. What Honda does say is to use
Top Tier gas and not to use fuel additives. The Top Tier program has specific requirements for the gasoline mixture itself as well as requirement on all stations for that brand regarding their pumping equipment and underground tanks. These requirements virtually eliminate water and sediments from entering your car's tank via the gas pump.