I did not opt for any winter additives in our heating oil and it has been very
cold here about 10 deg F during the day, -4 at night on the coldest.
Our furnace has trouble priming when the tank gets to half full and I was
thinking of adding this stuff - is it worth it?
I find it hard to believe that 16 oz per 275 gallons will do anything at all.

Any insight is appreciated.

 

I'm not sure what that product is.

Is the tank outside ?
Is the oil burner lower than the tank level ?
If you have an outdoor tank you can put kerosene in to stop the fuel from gelling.
If you have water in the tank.... that could be a problem.

 

Yes the tank is outside, no sign of water.
I think that the burner is at about the half way mark of the tank.

Here is the product:
https://www.amazon.com/FPPF-Chemical.../dp/B001E099MU

 

Hmmmmm...... sounds like a possible leak in the fuel line.

I'd not heard of that additive but it has many reviews on amazon and the bulk of them are favorable so it may be a good additive. Many people used two in their tanks.

 

Nothing wrong with HOT. Works well. It actually works best if added just before a delivery or pumped back into the tank via the burner inlet line.

 

I would not hesitate to use it and keep some on hand if it gets colder! single digits and below! Along with above advice on kerosene additive. My neighbor has just experienced some gelling in her tank and had a heating pipe burst on her. the oil company guys added some in her tank after her costly repair fiasco! (PREVENTIVE MAINTENANCE! )
Quick story: Oil gelled up, having trouble getting to burner from outdoor tank with insulated line. After a steady single digit few days and then a -10° day no oil flow. So oil service comes out and has 2-5 gallon tanks feeding her boiler with kerosene. few hours later unit stalls again, but lower zone not functioning correctly ( so instead of correcting problem????) they caution this poor women of problem.
Few hours later frozen pipe bursts in several locations then calls me for advice. I suggested getting a new oil company service. She claims they are convenient since they supply propane gas and oil service , YET NO plumbing services...... she had to outsource a plumber that was available for repair. I did not want to get more involved than I had to.

 

Thanks, I added it today, we have a 500 gal tank so I used two bottles, might get
two more to have on hand in case the temps drop again.
Our Oil company wants $59 per fill up for their winter additives - not sure what they are.

 

Here,s an idea; I have done it and it works. Make a wooden box to cover the tank. Insulate the inside of the box with 2 " styrofoam. Add a 100 watt light bulb and a manual switch with a light indicator (so you remember to turn it off) If you are really good at wiring use a line voltage thermostat set for 20 degrees. Below 20 degrees the light comes on and keeps the oil slightly warmer so it won't jgel

 

That sounds like a great idea, like something my dad would have said - he was a thermodynamics expert, but the tank is in the ground.
I put 2 bottles of HOT in and will get 2 more since the temps are dropping soon into the teens.

Is it a crazy idea to put a heater tape on the feed line? It is copper which is a good conductor to get
the heat down the pipe to the inlet.

Anyway, I don't mind adding the HOT in the very cold seasons, I'll probably add one bottle at the
start of the season, then more if the temps drop to the teens.

 

That really should have been in your first post.

If the tank is in the ground.... why aren't the lines ?