Measuring Heating Oil Consumption

General Information

One of the annoying problems with oil fired central heating systems is that there is often no gauge on the storage tank to say how much oil is left of if there is a gauge it is inaccurate or not properly calibrated. So often all that is left is to look in the tank to see how much oil is left or relying on the oil delivery company to keep the tank topped up at their convenience.

Making A Dipstick

There is however another way which costs almost nothing. That is to use an old fashioned dipstick which can be made very simply to provide quite accurate results and works for any shape of tank. To make a dipstick take a length of wood (new untreated thin beading is best) longer than the depth of your tank and cut notches in it at every measurement point with a knife or small saw. Using notches solves the problem that heating oil will over time remove most types of marker pen or paint. Measure the internal height of the tank in your preferred units and make up a dipstick divided equally in inches or centimetres up to the internal height of the tank, cutting a larger notch every foot or 10 centimetres as appropriate. See the tank types below for converting depth measurements to the amount of oil. It is important the dipstick is clean and not rotten or painted to avoid contamination of the oil.

Measuring How Much Oil Is Left

If you know the capacity of the tank in litres (or gallons) then a little bit of maths is required after measuring the depth of the oil in the tank using a suitable dipstick.

Rectangular Tanks: DIp the tank using the dipstick and the amount of oil is the depth of oil divided by the depth of the tank multiplied by the tank capacity. If the tank is bunded (double skinned) the depth of the tank is the depth of the inner tank.

Cylindrical Tanks On Their End: These can be treated exactly the same as rectangular tanks since the capacity varies linearly with depth. If the tank is bunded (double skinned) the depth of the tank is the depth of the inner tank.

Cylindrical Tanks On Their Side: These are a bit more complex since the amount of oil per unit depth varies depending on the level of oil in the tank. DIp the tank using a dipstick and the amount of oil can be found by using the table below which is for a 1000 units (gallons or litres) tank 100 units (inches or centimetres) deep. The oil depth in units is the depth of oil in the tank divided by the depth of the tank multiplied by 100. Look up the oil left for the unit depth measured in the table below and multiply by the tank capacity divided by 1000. To get a more accurate measurement sub divide evenly between each point - not totally accurate but OK. Remember cylindrical tanks normally have a neck which could hold up to another 20 litres over and above the nominal capacity, Cylindrical tanks can also have slightly rounded ends, for the purposes of monitoring oil consumption this does not significantly affect the accuracy of measurements. If the tank is bunded (double skinned) the depth of the tank is the depth of the inner tank.

Oil Depth (Units)	How Full (%)	Oil Left (Units)
10	10%	50
20	14%	140
30	25%	250
40	37%	370
50	50%	500
60	63%	630
70	75%	750
80	86%	860
90	95%	950
100	100%	1000

If you want a table specifically for your tank email us the details and we will publish a table on the Cylindrical Tank Capacity page.

Measurement Accuracy

For more information on how accurate the measurements are likely to be check out the heating oil measurement tips.

Also it is worth remembering that oil does expand and contract slightly with temperature so measuring the level with the tank in full sunlight will be slightly different to measuring it on a cool morning. To convert between litres and gallons or inches and centimetres or find out how much oil expands with changes in temperature look at the useful conversion factor page.

Keeping Records

With this information it is feasible to monitor oil consumption on a regular basis to identify whether savings are being achieved. To make this easier there is a choice of sheets in the record sheet section.

Miscellaneous

If your tank is not one of those above let us know and we will see if we can work out the formula.

It is a good idea to wear gloves when dipping the tank as the heating oil can irritate.

Another way of controlling oil consumption if you have more than one tank is to turn one of them off and run the heating until the other one is nearly empty. This is a good indicator a fill up is required but still allowing plenty of time to get the fill up done which allows some margin for picking a time when oil prices are at their lowest since they do vary with market conditions. Don't run tanks totally empty since if this occurs it may be necessary to bleed air out of the heating fuel system which can be costly if you can't do this yourself.

To help monitor oil use JSutils has produced two heating oil calculators called EnCalcOL and EnCalcOU which work based on tank depth or volume readings and copes with different shape tanks. They remove the need to do the maths yourself. EnCalcOU calculates cost and use, EnCalcOL calculates use. Both can also predict oil use. They are both free for personal non commercial use.