I added 2 bottles to my 275 gallon outdoor fuel tank. I had it filled with just normal #2 fuel oil. Just recently we had two days straight below zero, down to -18 degrees F and high winds. Never had any issues with the fuel hitting it's cloud point and gelling. The tank and line heading into my garage are not insulated in any way. I'm very happy with this stuff. Certainly cheaper than running kerosene.

We add this to our fuel oil every winter it it keeps it from gelling and burn efficiently!

my tank

I have an old tank, with equally old lines. Truth be told, i'll probably need to replace it in the next few years.

The entire system had been severely neglected. The tank was super sludgy, and kept clogging the filters and strainers, every few weeks in winter. Water in the lines was causing a coughing, uneven burn, and the boiler was noisy as hell. My boiler guy would come fix things, and it would run smooth for a while, but the root problem was the tank and lines.. he drained some oil at the boiler into a clear jar to show me what was coming out. (obvious sludge and water suspended in the fuel oil.)

I was full prepared to get a pricey pricey pricey system flush, drain, de-sludge and refill done. My heating guy is an old timer, oldschool dude, who doesn't charge me half the time if it's something easy and he's in the neighborhood (key point: he's an upstanding and honest fella, not trying to upsell me on things) told me to try this stuff first. Started me out with 2 bottles in a fresh tank, then one bottle per fill up for the rest of the season. See where we end up at the end of the season. If it's still a problem, he'll do the flush. He prefers the slow dissolve though, as it lowers the risk of something getting dislodged and creating a clog that requires replacing the under-cement lines.

There's no miracle "I noticed an immediate difference" story here. In fact he warned me i'd likely have to replace the filter catridges and clean the strainers a few times in a relatively short period of time as it de-gummed the tank and lines.
However over the course of the next couple of tank-fills, the boiler was working much more quietly... no more "burpipng" or sputtering, and the strainers were staying clean.

By the end of the season, the oil coming out at the boiler was clear red, with no signs of water or sludge. Filters are lasting longer, and strainers are squeaky clean upon inspection.

I use it every other tank now. About 3-4 bottles per heating season, depending on how cold the winter is. The boiler is the quietest I ever remember it, and when i replaced the filters in preparation for the heating season - left from last year - I probably didn't need to. Minimal gunk.

So - it did its job, I'm happy, and will continue to use it.

Received order promptly. Will use it in the winter. Now have the product and do not have to worry about it.