This M.Y. question discusses the permissibility of using approximations in halacha. It says:

The Sefer HaChinuch (Mitzvah 258) says explicitly that one may not rely on such estimations by Choshen Mishpat

I.e. regarding monetary transactions, one should be stringent and not rely on approximations.

In the U.S. (and I think Canada, also) the price of gasoline is always $x.xx and 9/10 of a cent per gallon. Unless one bought a multiple of 10 gallons, he would be paying more to the gas owner.

Based on this principle, how would it be permissible for a Jew to sell gas?

  • 1
    Is the problem not only when the buyer is being cheated but if the buyer knows what is happening and he forgives it, it is not a problem?
    – hazoriz
    Commented Apr 10, 2017 at 19:07
  • 2
    This question expands to the idea of approximations in Halacha in general no? Commented Apr 10, 2017 at 19:22
  • 1
    The Chinuch discussed using approximations that Chazal used, about whether one may rely on them since apparently Chazal did. I'm not sure that you can apply that principle over here.
    – DonielF
    Commented Apr 10, 2017 at 20:18
  • 1
    Besides, people seem to be mochel mills. Also, seemingly this question would be a case of ona'ah, whereas the choshen mishpat cases discussed by the Chinuch were ones in which the buyer didn't get what he paid for, a possible mekach ta'us. Here, he's paying an extra mill to the penny, a 10% overcharge, well within the ona'ah margin.
    – DonielF
    Commented Apr 10, 2017 at 20:22
  • 1
    "Unless one bought a multiple of 10 gallons, he would be paying more to the gas owner." No, if the price is $1.009/gallon and he bought six gallons, he'd pay $6.05, an underpayment. (At least, I think that's how it works.)
    – msh210
    Commented Apr 11, 2017 at 20:26

1 Answer 1


I don't see the stated problem here. Gasoline is a continuous fluid to more digits than we can actually measure with the comparatively crude instruments used in gas pumps.

He's not selling a gallon of gas for 4.009; he's selling 10/4009 gallons for a penny.

There's actually a worse problem that reached mild fame here in the US before dying away. Gas station pumps don't have the temperature correcting hardware they do everywhere else for historical reasons. The amount of gas you sell varies a couple of percent based on the temperature came out of the delivery truck (it usually doesn't sit int the tank long enough to equalize with the underground temperature--that takes weeks), and the truck's meter corrects for temperature, so the station pays for the gas temperature corrected. But the cost of the temperature correcting hardware outweighs the average consumer loss, so it doesn't get fixed (the cost of the correction would inevitably be passed onto the consumer, mostly by driving ancient rural gas stations out of business).

I suppose one could special order fuel pumps that actually do temperature correction (they do exist--Canada uses them), but the evaluation across the entire industry in the US is it would end up costing the consumer more than just eating the error. Gas stations are extremely thin margin (they tell me it's less than a penny a gallon) so the only place that money can come from is higher prices, and consumers are extremely price sensitive and bad at evaluating value. You could get a little extra popularity from advertising that you do temperature correction, but it probably won't tip the scale.

So if you care about accuracy, the 9/10 of a cent isn't the problem. The fuel volume change with temperature is.

  • Why don't they just adjust the advertised price based on the temperature? Then they're not lying.
    – Heshy
    Commented Jun 19, 2019 at 23:18
  • @Heshy: Not sure how you'd do that. The fuel pump is going to display the uncorrected gallon measurement. While a correcting fuel pump is lawful, patching in the correction externally is gonna fail an audit.
    – Joshua
    Commented Jun 19, 2019 at 23:37
  • @Joshua I think the suggestion is not to adjust the number of gallons shown on the display based on temperature, but rather to adjust the price based on temperature. So when the weather causes the pump to over-report gallons, reduce the price accordingly and vice-versa.
    – Daniel
    Commented Jun 20, 2019 at 3:11
  • I guess it's still misleading if you do it that way because the customer now thinks the reduced price is for temperature-corrected volume.
    – Daniel
    Commented Jun 20, 2019 at 3:17

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .