Winter Storage: To Fill or Not to Fill Fuel Tank

[GeorgeOCanada]

Hi Everyone. I know this is a depressing topic (winter storage) for most of us. I live in Ontario Canada and the winters here can be pretty brutal and they put a lot of crap on the roads that's not good for any car. For the most part I'm comfortable with the winter storage procedure for my Corvette (2017 Z06) and I know what to do.

There is one item however where most forums I've visited the members had differing opinions. If possible I would like to keep this thread focused on this one aspect of winter storage, and that is, do I fill the gas tank or quarter fill the tank for winter storage?

The argument for the conventional "full tank" procedure is condensation prevention. This is what I've been doing for all my past cars (all non-Corvette).

There are many posts in other forums that cite a remark/quote from Paul Koerner that says you should quarter fill your gas tank. I believe this is for C7 Corvettes, but I'm not sure. The argument here is, when the tank is full, the lower positioning of the fuel gauge sending unit makes it vulnerable to sulfur contamination on the sending unit contacts which ultimately damage the unit causing inaccurate fuel gauge readings. As well, the quote goes on to say that for C7 fuel systems the condensation issue is not relevant based on how the tank and fuel system was engineered, and you can quarter fill your tank with no condensation worries.

Does anyone know where I can find this original quote from Paul Koerner, as I do trust his opinion. Are there any Corvette mechanics out there that have serviced/replaced sending units because of long term full tank storage? What is your opinion/recommendation?

Thanks Everyone.

[LLC5]

Condensation is going to happen, and more so with more oxygen in the fuel tank no matter the vehicle. Plastic fuel tanks don't rust but I don't like the idea of helping water collect.

It is a little humorous to think that a part designed to live it's life in fuel should also be kept away from fuel to keep it from sulfating.

That being said, I have never had an issue with any of my vehicles (lots of them over decades) keeping the fuel tanks full and having a fuel sending unit go bad, but I have replaced both fuel senders in my C5 and they were both sulfated profusely and it wasn't from storage I use it year 'round just less in the winter. If you find the article that Paul wrote let us know, he is the authority on anything GM.

[GeorgeOCanada]

Condensation is going to happen, and more so with more oxygen in the fuel tank no matter the vehicle. Plastic fuel tanks don't rust but I don't like the idea of helping water collect.

It is a little humorous to think that a part designed to live it's life in fuel should also be kept away from fuel to keep it from sulfating.

That being said, I have never had an issue with any of my vehicles (lots of them over decades) keeping the fuel tanks full and having a fuel sending unit go bad, but I have replaced both fuel senders in my C5 and they were both sulfated profusely and it wasn't from storage I use it year 'round just less in the winter. If you find the article that Paul wrote let us know, he is the authority on anything GM.

Thank you for your comment and insight.

Below is one rendition I found of what Paul allegedly said. This is what I'm trying to validate. The quote is a bit confusing in that he recommends a 1/4 tank for gens 4 thru to 7 but goes on to indicate the condensation issue is a non-problem for C7's. I've been digging around for a week with no luck. It would be great if Paul himself could comment. Please note the comment on moisture build-up for C7's. Thanks again for your help.

"[I]Also, if you plan to store your C7 for longer than one month, Paul Koerner emphasizes the following points. Review your owner's manual for more storage recommendations (battery tender, ect.).

- Store newer Generation (4 through 7) with 1/4 tank of gas.
- Use fuel stabilizer if storing for longer than one month at a time.
- Change oil before storage

The reason for only storing with 1/4 tank of gas has to do with the location of the fuel sending unit. In the C7, the fuel sending units are half way up inside each of the two tanks. Sulfur in the gasoline can coat the fuel level sensors, causing the fuel gauge to become inoperative. The reason that this does not happen when you are regularly driving the car is that movement of the gas in the tanks keeps the contacts clear. In order to clean the contacts, use a 20 ounce bottle of Chevron Techron Fuel System Cleaner (Auto Zone, etc.). The old reasons for storing with a full tank of gas no longer apply with the C7. The double sealed fuel filler neck and the charcoal canister on the other side of the tank prevent moisture build up from taking place. "

[LLC5]

Thank you for your comment and insight.

Below is one rendition I found of what Paul allegedly said. This is what I'm trying to validate. The quote is a bit confusing in that he recommends a 1/4 tank for gens 4 thru to 7 but goes on to indicate the condensation issue is a non-problem for C7's. I've been digging around for a week with no luck. It would be great if Paul himself could comment. Please note the comment on moisture build-up for C7's. Thanks again for your help.

"[I]Also, if you plan to store your C7 for longer than one month, Paul Koerner emphasizes the following points. Review your owner's manual for more storage recommendations (battery tender, ect.).

- Store newer Generation (4 through 7) with 1/4 tank of gas.
- Use fuel stabilizer if storing for longer than one month at a time.
- Change oil before storage

The reason for only storing with 1/4 tank of gas has to do with the location of the fuel sending unit. In the C7, the fuel sending units are half way up inside each of the two tanks. Sulfur in the gasoline can coat the fuel level sensors, causing the fuel gauge to become inoperative. The reason that this does not happen when you are regularly driving the car is that movement of the gas in the tanks keeps the contacts clear. In order to clean the contacts, use a 20 ounce bottle of Chevron Techron Fuel System Cleaner (Auto Zone, etc.).

I might take a slight exception to the moisture aspect, 3/4 tank of oxygen (or about) with extreme temperature changes will create a certain amount of condensation, fully sealed tanks do help with outside moisture coming in. If in doubt go with what Paul says, he is the GM expert.

Last edited by LLC5; Today at 05:11 AM.

[GeorgeOCanada]

I've traced the original quote from Paul Koerner to a post from a senior member on corvetteforum.com. I sent a private message to that member inquiring about the origin of his post. He made his post after hearing it from Paul at a seminar Paul presented. Below is his response to my inquiry.

"Hi George! Welcome and congrats on your new 2017 Z06! The information that I have provided from Paul Koerner came from one of his seminars that I have attended in the past. He reviewed the post on the forum and made sure the information was correct. I hope this helps. :cheers:"

This is good enough for me to use the recommendation of a 1/4 tank for winter storage. Hope this is helpful to other folks putting their "late model" vets into hibernation.

[markw8]

Just my 2 cents. I've had my 01 since 2003. It currently has @ 33k miles. It has always been stored in the winter with a full, or nearly tank. It has only had stabilizer added, maybe half the time. It usually is put away, mid Nov to early April. I try to use top tier gas and it gets maybe two treatments of Textron Plus a season. I have had zero fuel sender problems. Maybe I'm just lucky, but it works for me.

Mark