Heating oil: methods

Registered July 2026, one year before the deadline. This page states how the No. 4 oil phaseout is scored, so the methodology can't bend to the results.

What No. 4 oil is, plainly

Heating oils are graded by thickness. No. 2 is the thin oil most houses burn - close to diesel. No. 6 was the other extreme: the heavy, tar-like residue left over from refining, so thick it had to be heated just to flow, and the sootiest thing burned in the city. No. 4 is a blend of the two - cheaper than clean fuel, dirtier than it, one step up from the bottom. Big apartment buildings burned No. 6 and No. 4 for decades because they were cheap; the soot they put into the air is why the city started banning them.

Why this fight started

In 2011, when the city began forcing heavy oil out, roughly 10,000 buildings - about one percent of the building stock - burned No. 4 or No. 6, and together they put out more soot than every car and truck on the city's streets combined [EDF]. The soot is fine particulate matter, PM2.5: particles small enough to reach deep into the lungs, a trigger for asthma attacks. The heavy grades emit up to 15 times more of it than No. 2 oil or natural gas [EDF].

The promise

Local Law 32 of 2023 ends the burning of No. 4 heating oil in New York City on July 1, 2027. It is the last chapter of the phaseout that removed No. 6 oil in 2015. The law is a number and a date: zero boilers, July 2027.

The metric

The count of boilers holding a permit marked CURRENT (the database's own label for an active permit) in the Department of Environmental Protection's Clean Air Tracking System that lists No. 4 oil as primary or secondary fuel. Read monthly, reported with its as-of date. The measure is met when the count is zero on July 1, 2027; every month before that simply reports the number and its change.

Baseline, July 2026: 561 boilers - 312 burning No. 4 as primary fuel, 249 holding it as backup. 240 sit in the Bronx and 220 in Manhattan.

Who is left, and why there

The borough skew is baked into the buildings. The city only permits boilers above apartment-house scale, so the countdown list is by definition a list of large multifamily buildings, and the agency's own map of No. 4 boilers clusters up Manhattan and into the Bronx [DEP]. The exposure is not evenly shared: in the city's tally of No. 4-only boilers, 61 percent sat in state-designated environmental justice areas - neighborhoods flagged as low-income or already overburdened by pollution [DEP]. The exits are closing on schedule: no No. 4 permit has been issued or renewed since June 2024, holdouts face penalties up to $10,000, and the city's NYC Accelerator program offers owners free help planning the switch [Accelerator]. The 249 buildings holding No. 4 only as backup face the lowest conversion costs of all, by the city's own analysis [DEP].

Judgment calls

• Secondary-fuel permits count. A boiler permitted to burn No. 4 as backup is still permitted to burn it; the law bans the use, not the label.
• A permit that expires without renewal leaves the count; that is the mechanism working, not a loophole.
• The count is permits, not smoke: a building can hold a permit and burn gas all winter. The permit is what the law regulates and what the public record shows.

Data

DEP Clean Air Tracking System (CATS) permits, NYC Open Data. Updated continuously; this measure reads it monthly.