Great video. I would enjoy seeing more like this. It reflects the real life applications of the standards for which the NIST is responsible, and explains how they apply to normal citizens on a daily basis.

Why are multiple grades of product allowed to be dispensed through a single hose ? Based on my estimate of 13 feet of 3/4 inch hose and 8 feet of 3/4 inch tubing internal to the dispenser there is almost 1/2 gallon of lower grade fuel dispensed to a customer buying 93 octane fuel when the the previous customer bought 87 octane rated fuel and vice versa . With a difference of $0.40~$0.50 between grades that is like the meter jumping 20 to 25 cents.

@NIST

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+Mike Rue Gasoline dispensers that offer more than one grade of gasoline often dispense more than one grade of product through a single hose. As you have noted, the hoses on dispensing systems of this design do contain a residual amount of the product dispensed during the previous delivery, and this residual amount is unavoidable. As to why the marketplace has permitted this variation, there are likely several factors. One is the convenience offered to the consumer of purchasing intermediate blends of fuel at the dispenser. Additionally, it is significant to note that the octane of the residual fuel will not always be lower than the octane selected in the subsequent purchase. While in some instances the residual amount remaining in the hose will be at a lower grade than the subsequent purchaser selected, in other instances when the previous delivery was either the intermediate (blended) grade or the high octane grade, the grade will be equal to or higher than the grade selected by the purchaser. Most states have octane sampling programs where inspectors draw samples of fuel from a station and determine its actual octane content through laboratory testing. The samples must comply with the posted octane content of the fuel, regardless of the design of the dispenser. Note that there are dispensers that have dedicated hoses for low and high octane fuel as well as for an intermediate octane fuel. One option to avoid the scenario you referenced is to shop at a location where such equipment is available when you plan to purchase higher octane fuel. Another thought is to express your concerns to the station owner regarding the effect of the residual amount. While this won’t likely assist you in your current purchase, it will make the owner aware of the concerns of his or her customers.

When will I be able to buy by the liter?

Ok I work in the compliance industry and I calibrate dispensers daily and I your video the guy doing the calibration is allowing a customer to dispense fuel on the other side of the pump while he is doing the calibration. That is a fault and makes the calibration in accurate. The pump being calibrated should be completely blocked off so there is not fuel being pumped of the same grade coming from the meter. Yes there is technically two meters per grade but only one pipe coming from the tank. This could lead to a discrepancy in the calibration.