A quick guide to spotting warm oil lines with an IR camera

I had a similar thing happen with my older unit last fall, but it wasn't the pump heat you described. My concern was more about what was happening after the oil left the storage tank and started moving toward the heat exchanger. I used a digital probe to monitor the temperature along the supply run before it went into the main manifold. I saw the temperature start at 135 degrees right off the filter and then steadily drop til it hit the burner, settling around 118 degrees. That fifty-seven degree drop over the span of maybe thirty feet of line caught my attention. It wasn't a huge difference, but it felt wasteful. I figured there was significant heat loss somewhere in the piping or maybe the line gauge itself was slightly too undersized for the volume of oil my furnace pulls through. Even if your circulation loop is running hot and helping the burn, losing energy externally before it ever reaches the primary components seems just as bad for efficiency. It makes me wonder if there's a good way to calculate the heat transfer rate based on line material and ambient temperature. I tried wrapping the sections with extra foam insulation but noticed the temperature drop barely changed, which suggests the loss is probably structural or related to the fittings rather than just the pipe itself.

That warm loop thing tracks with what I saw at my place. My tank lives in an unattached garage and every February the line to the house whould get sluggish and the burner would get loud and hunting. Scanned the run with a cheap spot thermometer one cold morning and the section along the outside wall was barely above the garage temp while everythign inside was fine. What actually fixed it for me was not insulation, it was rerouting that one stretch to run thru the heated mudroom instead. Went from yearly sputtering to zero issues in three winters now. Reading this I'm guessing my pump loop keeps the whole return side nice and warm too, never thought of it as a feature until now.

Same deal with the foam not helping. I wrapped my loop one winter thinking I'd hold that warmth in for the burner and it barely moved the needle, which makes sense if the pump itself is what's heating the oil in the first place. The thing I noticed with mine is how fast it all cools once the burner shuts off for the night. By morning the housing is back down to room temp and the first cold start of the day sounds rougher than the rest. Once it's been cycling a while that loop is hot again and the burn quiets right down.

Update: tried tracking the cooldown after a run, since one reply said the loop drops fast once the burner stops. Sure enugh, within maybe half an hour everything was back down near room temp. Which got me thinking, my tank is in a crawlspace like the garage setup mentioned above, so I'm wondering if I should be scanning that supply run on a cold morning to see if the oil's sluggish before it even reaches the filter.