How to Read Your Oil Tank Gauge (and When to Order)
From the Alcus family · Alcus Fuel Oil & Sons, Amityville · Updated October 30, 2026
Most basement oil tanks have a simple float gauge on top: a clear dome with a red or orange marker inside. The marker floats on the oil and shows how full the tank is — F, 3/4, 1/2, 1/4, E.
Reading it
- Find the gauge on top of the tank (usually near the fill pipe end).
- Look at the top of the marker against the marks on the side of the dome.
- If the marker is sitting at the bottom or you can't see it, the tank is at or near empty — or the gauge is stuck. Press the top gently to check it moves.
Gallons left in a 275-gallon tank
| Gauge reads | About this much oil | What to do |
|---|---|---|
| F (full) | ~225–250 gal | You're set |
| 3/4 | ~170–190 gal | Check again in a week or two in winter |
| 1/2 | ~120–130 gal | Plan your next delivery |
| 1/4 | ~55–65 gal | Order now |
| E | Almost nothing usable | Call us right away |
Tanks aren't perfect rectangles, so these are estimates. A 330-gallon tank holds about 20% more at each mark.
How many days do I have left?
Divide the gallons left by how much you burn per day: maybe 2–3 gallons on a mild day and 6–8 on a very cold one for a typical home. Our calculator does the math for you, and this guide explains what changes your usage.
Never read the gauge again
With automatic delivery, we use the weather and your past deliveries to know when you'll need oil, and come before you run low. Prefer to call when you need it? Order online or call 631-264-8800.
Need oil or service on the South Shore?
Questions
How many gallons are left when my 275 gauge says 1/4?
Roughly 60 gallons. That is a few days to a couple of weeks of heat depending on the weather, so 1/4 is the time to order.
My gauge is stuck. What do I do?
Gently press the top of the gauge or tap the cap. If it still does not move, do not guess — call us and order. A sticky gauge is easy to replace at your next service visit.
How much oil can you fit in my tank?
Subtract what you have from about 225–250 gallons for a 275 tank (about 280–300 for a 330). Or just ask for a fill and we fill it safely.