Does the temperature affect accuracy of fuel pumps?

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Sat 12 Sep 2015 11:49
Does the temperature affect accuracy of fuel pumps? - Mark Wallace

I was filling my car up this morning and noticed that the petrol pump, next to the read out shoiwng how many litres I put into the tank, had (at 15 degrees C) stuck next to it.

does the tempertue effect the accuraucy of the pumps? If so, how much by? DO I get more in my tank if I fill up on a hot, or cold, day?

Edited by Avant on 13/09/2015 at 00:43

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Sat 12 Sep 2015 12:07
Does the temperature effect accuracy of fuel pumps - Chris M

I seem to recall that the petrol retailers used to complain that the fuel was delivered to the forecourt in tankers which would, especially in summer, be warmer than the storage tanks underground. So they would be buying 10,000 litres at say 20 degrees C and sell it at 5 degrees C. I don't know how much petrol expands as it warms, but it must make some difference for it to be an issue for the retailers.

For the punter, we are buying x litres as messured by the pump and that must be accurate as Trading Standards would demand it. We buy the fuel at 5 degrees C and it will usually (except in winter) warm up in the car's tank

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Sat 12 Sep 2015 13:54
Does the temperature effect accuracy of fuel pumps - RT

The pumps accurately measure volume, no difference hot or cold - but the fuel expands as it gets warmer so a litre of cold fuel will weigh more than a litre of warm fuel and contain more energy.

As fuel tanks are underground at filling stations, the effect of climate is small but it is better to refuel in the morning, theoretically at least.

As an aside, modern pumps are a lot more accurate than Trading Standards require so they're usually set to take advantage of the permitted tolerance - that's taking advantage from the filling station's point of view, not the customer!

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Sat 12 Sep 2015 18:11
Does the temperature effect accuracy of fuel pumps - 72 dudes

As fuel tanks are underground at filling stations, the effect of climate is small but it is better to refuel in the morning, theoretically at least.

Correct, whenever we print off a tank ullage reading, the temperature in each tank is shown. In summer it's around 14C, on a cold winter day it might be 8 or 9C, so not a huge difference.

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Sun 13 Sep 2015 00:27
Does the temperature affect accuracy of fuel pumps - ExA35Owner

The thermal expansion coefficient of petroleum is about 0.001 per degree C. So the 5 degree difference would make about 0.5% difference to volume, probably not enough for the motorist to worry about.

Edited by ExA35Owner on 13/09/2015 at 00:27

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Sun 13 Sep 2015 10:59
Does the temperature effect accuracy of fuel pumps - Andrew-T

The pumps accurately measure volume, no difference hot or cold - but the fuel expands as it gets warmer so a litre of cold fuel will weigh more than a litre of warm fuel and contain more energy.

In essence true, except that pumps are no more immune from thermal expansion than fuel. The point is that the fluid expands differently from the container. Why we can use a mercury-in-glass thermometer, for instance.

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Sun 13 Sep 2015 20:15
Does the temperature affect accuracy of fuel pumps? - TedCrilly

Call me the cynic but If ambient temperature really did make a significant difference to the bottom line the oil companies and the retailers would be using heaters (set in their favour of course) on the tanks and pumps.......wouldnt they?

Science says there is some truth in it all but 10 minutes spent in the toilet prior to setting off and the consequent saving in weight would probably be of more benefit.

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