Fuel variance — the “ghost gallons” problem

Variance is the gap between two numbers that should agree: the book (yesterday's stick + deliveries − sales) and today's stick (what's actually in the tank). A negative variance means fuel is missing — ghost gallons. A positive one means the tank holds more than the book expects, which is usually a paperwork error rather than a gift.

How much variance is normal?

Some. Sticks are read to the nearest eighth of an inch, tank charts are approximations, fuel expands on a hot afternoon, and pump meters are mechanical devices with legal tolerances. A few gallons a day either way is noise. Two working lines:

• Daily flag rule: over 50 gallons, or over 0.5% of that day's sales — whichever is bigger — deserves a same-day recheck.
• The formal monthly standard: federal inventory control compares book to stick monthly and treats a gap beyond 1% of the month's flow-through plus 130 gallons as the line that must be investigated. Over that line two months in a row, it can become a suspected-release report. Variance is not just money — handled wrong, it becomes a compliance event.

The five usual causes, in the order to check them

1. A misread stick or a mistyped number. Cheapest cause, most common. Recheck the stick before you suspect anything else — and check the totalizer was written down right.
2. A short delivery. The ticket says 4,000 gallons; the tank gained 3,830. This is why you stick before and after a drop: book-vs-stick on a delivery day separates a short load from everything else. Raise it with your distributor while the load is fresh.
3. A drifting pump meter. A meter that registers more than it dispenses manufactures missing gallons on paper, a little every day. The signature is a steady negative variance on one grade that grows with sales volume. Meters can be tested and recalibrated.
4. A leak. The serious one. A variance that repeats daily, in the same direction, with clean readings and honest deliveries, is a leak until proven otherwise — and a suspected leak carries reporting duties with deadlines. Don't sit on a pattern.
5. Theft. Fuel leaving without passing a meter — after-hours pumping, test-mode abuse. The signature is variance concentrated on certain days or shifts. Daily numbers are what turn a suspicion into a timeline.

Why the daily habit beats the monthly discovery

On paper, most owners meet their variance at month-end — as one lump sum with no story attached. Daily, every flag arrives with its day, its delivery, and its readings still warm. That is the difference between “we're short 900 gallons this month” and “Tuesday's load was short — here's the before-and-after stick.”

Official source for the monthly standard: 40 CFR Part 280, Subpart D (federal UST release-detection rules, including inventory control). The 0.5% daily line is a widely used industry rule of thumb, not a regulation.

See your variance today — free book

More guides: Daily tank reconciliation · The UST inventory log · Days-to-empty