We get this question a lot! No, it will not harm your diesel truck. High Mileage is safe in diesel engines (and will still clean), but it is not formulated for diesel additive requirements. You’re completely fine to keep driving your truck as normal.

Good question, Valerie.

I’d use the High Mileage formula for your truck. It’s made to clean stubborn fuel residues, so it would be a great option for getting your truck running strong again. Here’s what I’d do: add two 16-ounce cans of High Mileage to the tank. Then, drive it as normal until it’s almost empty before refueling. You want to make it through as much of the treated fuel as possible. The high concentration will do a great job cleaning up any fuel residues or deposits that formed while it sat.

After that, add a can of Truck & SUV to a ¼ tank every 3,000 miles or so to keep the fuel system clean. You could also keep using High Mileage as well if you want.

Let me know if you have any other questions – happy to help!

Best,

Conner

Sea Foam

Thanks for the question, Quinn! I’d use Sea Foam High Mileage. It’s made exactly for that – to clean up a fuel system after years of buildup. It will work to clean fuel injectors.

Here’s what I’d do: wait until the tank is low (1/4 -1/8 tank), and add the whole 16 oz can. Then, drive for as long as possible on that tank before refueling. It’s safe to add a high concentration like that and it works very well for cleaning fuel residues and deposits.

Good question, Erasto. Our standard recommendation is to add it 100-300 miles before you change your oil. That gives it enough time to circulate and clean, and then allows the reliquefied residues and deposits to be drained away with the old oil. 

If you’ve already added it, you can leave High Mileage in the oil crankcase for 1,000 miles before you change your oil. It won’t harm anything and it will work to clean and reliquefy oil residues.