Thanks for the question!

If the tank is already full, I’d add 1–2 ounces of Sea Foam per gallon of fuel.

That said, the best cleaning results come from using a higher concentration. Here’s what I’d do:

• Drive it until the tank is down to about 1/4 tank or less
• Add a full 16 oz can (or even 2 cans)
• Drive it 10–20 miles (or until nearly empty) before refueling

Fuel that sits can form gum and varnish, which is the #1 cause of rough running after storage. Sea Foam works to liquefy and clear that out to help your engine maintain or recover strong performance.

Thanks for the question!

It depends on what you’re trying to do. Here are a few good guidelines:

For regular use / preventative maintenance:

Add 1 ounce of Sea Foam per gallon of fuel.
This keeps the fuel system clean and helps prevent gum and varnish from forming.

For cleaning (best results):

Use a higher concentration. I like to:

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

The higher concentration works better and faster to clean fuel residues and deposits.

For storage / protecting fuel:

Add 1 ounce (or more) per gallon of fuel before storing.
Sea Foam will help stabilize the fuel and prevent gum and varnish from forming while it sits.

No need to be exact with measurements. Sea Foam is petroleum-based and okay to use in higher concentrations.

Hope that helps and let me know if you have any other questions!

Good question, Dave. For a car or truck, we recommend every 3-5,000 miles, or once a year. That’s sufficient to keep things running clean. For small engines, run it once a year.

Good question, Greg. You can add Sea Foam as frequently as you’d like  – there’s no concern there. Running a high cleaning concentration like you described is a good idea. If the stuttering is caused by fuel-related issues (like varnish, etc), the Sea Foam will help clean it up. I’d recommend adding a 16 oz can of High Mileage to 2-3 gallons of fuel, and then driving at least 20 minutes (or as long as you are comfortable) to use up as much of the treated fuel as possible. Then, refill your tank as normal.