Great question, Neal. There’s two things I’d think about when considering fuel that sits for a while. First, you’ll want to think about cleaning up any fuel varnish that formed while the fuel sat. Second, you’ll want to think about preventing varnish from forming during future periods of inactivity, as well as preserving the fuel’s ignition vapors.

A tank of fuel that sat for three months will still be just fine to run.

I’d take two simple steps:

• First, especially if you’ve never done it before, run a strong cleaning concentration of Sea Foam High Mileage through your Sienna. That will clean up and fuel residues and deposits throughout the whole fuel system. It’s a great thing to do in any vehicle. A quarter tank is actually a perfect time to add Sea Foam. Here’s what I’d do: add an entire 16 oz can of Sea Foam High Mileage to your fuel tank, drive until almost empty (just don’t run out of gas), and then refill your tank. The high cleaning concentration will work much better and faster than adding Sea Foam to a full tank.
• Second, you can protect the fuel that sits in the tank by adding a can of Sea Foam High Mileage (or Motor Treatment) to every tank of fuel. Just add it before you fill up. That will help prevent gum and varnish from forming and prevent the fuel from degrading.

Hey Lonzo,

Thanks for the question. Yes, you can use High Mileage for your 2024 Civic. High Mileage is a great cleaner – it’s formulated to clean stubborn deposits and residues after years of buildup. But you can absolutely use it in a lower mileage vehicle too. It’ll do a good job cleaning up the fuel system.

Here’s what I’d do:

• Wait until the tank is low (about 1/4 tank or less)
• Add a full 16 oz can of High Mileage
• Drive at least 10–20 miles (or until nearly empty) before refueling

The high concentration works much better and faster to clean fuel residues and deposits than adding the same amount to a full tank.

Thanks for the question!

Yes, you can use another treatment right away. I’d recommend High Mileage Sea Foam since it’s formulated to be a strong cleaner for stubborn fuel residues and deposits. Here’s what I’d do:

• Wait until the tank is low (about 1/4 tank or less)
• Add a full 16 oz can of High Mileage
• Drive at least 10–20 miles (or until nearly empty) before refueling

The high concentration works much better and faster to clean fuel residues and deposits than adding the same amount to a full tank.

If deposits are causing the remaining rough idle and stalling, another high-concentration cleaning treatment should help. If the problem continues after cleaning, there may be another mechanical or ignition issue that needs to be checked.

Good question, Ron. With 177,000 miles, I’d recommend High Mileage Sea Foam Motor Treatment. It’s formulated as a strong cleaner for stubborn fuel residues and deposits that tend to build up in higher-mileage engines.

Since you’re noticing some sluggishness, here’s what I’d do to get the most out of a can of High Mileage:

• Wait until the tank is low (about 1/4 tank or less)
• Add a full 16 oz can of High Mileage
• Drive at least 10-20 miles (or until nearly empty) before refueling

The high concentration works much better and faster to clean fuel injectors and other fuel system deposits. If deposits are contributing to the sluggish performance, cleaning them up can help restore lost performance.

Once it’s running well, you don’t necessarily need to use Sea Foam more often because of the mileage. For preventative maintenance, add 1-2 oz per gallon periodically to help keep everything clean.