How to Read Your Heating Oil Tank Gauge

Written by Davenport Energy

A heating oil gauge does not read in gallons. It reads in fractions, and that one fact is behind most of the surprise run-outs we get called about. Here is how to read yours, and what the number means for how long you have.

Where the gauge is and what it looks like

Most home oil tanks use a float gauge mounted on top of the tank, under a clear plastic dome about the size of a teacup. Inside the dome is a disc or a small red marker that rides up and down on a float arm. The face is marked F, three quarters, one half, one quarter and E. Wipe the dome with a cloth if it has gone cloudy, because a basement tank collects dust and the marker hides behind it.

If your tank sits outside, read it in daylight and look straight down rather than at an angle. Reading a float gauge from the side is the easiest way to be a quarter tank out.

Turning a fraction into gallons

The fraction is a fraction of the tank, so you need the tank size to get to gallons. A 275 gallon tank is the common one in Virginia homes. There is more on sizing in our guide to home heating oil, which covers the whole picture from delivery to tank care.

Gauge reading	275 gallon tank	330 gallon tank
Full	about 250 gallons	about 300 gallons
Three quarters	about 190 gallons	about 225 gallons
One half	about 125 gallons	about 150 gallons
One quarter	about 68 gallons	about 80 gallons
One eighth	about 34 gallons	about 40 gallons

A full tank does not hold its stamped size. A 275 gallon tank is filled to roughly 250 gallons so there is room for the oil to expand, which is why a fresh delivery does not push the marker hard against F.

The reading that should make you call

One quarter is the number to act on. At a quarter you have roughly 68 gallons in a 275 gallon tank, and in a cold Virginia January a house can move through 5 to 7 gallons a day. That is about ten days, less if the weather turns, and delivery runs on routes rather than on demand.

Below an eighth, stop estimating and call. The last of a tank is where sediment sits, and running a tank dry pulls that sediment toward the line. If you have already run out, here is what to do next.

Learning your own burn rate

Write down the reading and the date, then do it again two weeks later. The difference across those two weeks, in gallons, divided by the number of days, is your burn rate in the weather you have just had. Two readings in November and two in January will tell you more about your house than any average.

That is also the arithmetic we do for you on Automatic Delivery, using your own history rather than a calendar, so nobody at the house has to watch the dome at all.

Frequently asked questions

Why does my gauge still read full after a week of cold weather?

A float gauge can stick, particularly on an older tank. Tap the dome gently and see whether the marker settles. If it has not moved in two weeks of real cold, treat the reading as unknown and call us rather than trusting it.

Is there a gauge that reads in gallons?

Wireless tank monitors read the level and send it to a phone. Ask us whether one suits your setup. On Automatic Delivery it is not something you need, because the scheduling is already done from your usage.

My tank has no gauge at all. What then?

Some older tanks never had one, and some have had the dome broken off. Call us and go on Automatic Delivery, because without a gauge a will-call setup has nothing to work from.

If you would rather not think about the gauge at all, that is what Automatic Delivery is for. We work the timing out from how your household actually burns fuel and come before you get low.

Background reading from the US Energy Information Administration: heating oil explained.

Heating oil delivery across Southern Virginia and North Carolina