1 qt. Sludge Treat

I have been using "Hercules Sludge Treat," annually/every oil-fill of my heating oil tank for a decade and IT WORKS GREAT at keeping the tank's filter and fuel-line clean, thus prevent them from from clogging with that "tarry goop" of black sludge that would otherwise cause furnace's "breakdown" every few years. After 6 years since last performing the change, I replaced the filter last year and was AMAZED as to how CLEAN it was (no black "goop" surrounding it as would always had been the case without the use of "Sludge Treat"). I have no doubt that this product is ALSO gradually reducing (perhaps even have by now eliminated) any accumulated sludge WITHIN my ancient tank, as well. HOWEVER, the child-proof design of the "new?" caps on these bottles are seriously flawed (I could not, NO-HOW, untwist them to get the bottles open (and there were THREE quarts/bottles in my order)! The "teeth" which are supposed to engage when the caps are pressed down simply cannot be caused to meet, no matter HOW hard down the caps are pressed while turning. What I had to resort to doing in order for them to be unscrewed was to use a sharp box-cutting tool, to SLICE AWAY A FRACTION OF AN INCH from the bottom edge of the outer/top cap. Only then did this permit enough clearance to allow the concealed, opposing "gears" withIN the cap to mesh and enable the caps' removal and then-normal operation (as only 1/4 of each quart's contents are needed for each partial-fill of a 250-gallon tank, I didn't want to destroy the integrity of either cap/bottle in entirety)!

Used for years but now in New York can only buy bio fuels I emailed Hercules and they told me it is NOT RECCOMENDED for bio fuels