If I pull up to a pump that had been pumping regular gas for the previous customer and I want to purchase only one gallon of high test for a special needs engine, will I get one gallon of high test if I push the button indicating a desire to purchase high test gas? Or, will I only get the remainder of the regular gas that was in the hose plus the remainder being high test? I know it may sound stupid but I don’t want a gallon that isn’t all high test.
You’ll get some regular, so if it’s that important pump some high test into your car, then the gas can.
This is an issue I have with one of my motorcycles.
You need to go to the station with separate hoses for each grade…
Those are getting harder and harder to find around my area.
You could wait for someone to fill up with premium, then buy from the same pump. Or, pump a few seconds of gas in your (or someone else’s) car, then fill up your one gallon container.
Not to ask the obvious, but…why is it a big deal? If you put 10 gallons of gas into a car, maybe a quart or two will be of whatever the previous type was. From that, the difference is at absolute worst is less than half an octane unit for the whole tank. Also, pretty much every modern car listens to itself and, if it’s hearing signs of low octane gas, adjusts its engine timing to compensate: it’s not going to hurt anything at all.
This is an issue I have with one of my motorcycles. You need to go to the station with separate hoses for each grade...
Those are hard to find. And every time one of those gas stations gets upgraded they go to the 1 hose design. 5 years from now you may not find one.
Ugh, sorry to be so silly: just reread your original post. texases comment sounds great.
You might try to goggle search how much gas is in the hose from the previous gas purchase. Some of this depends on the length of the hose. In most typical gas pumps I’ve heard it is about 1/2 gallon. If you want only one gallon of premium and the pump dispensed regular to the prior customer, you will get about 1/2 gallon of regular and then 1/2 gallon of premium in your one gallon tank.
You could add octane booster to your gallon to be safe, but doing what texases says is easier.
@Made - any chance you’ll let us know why you need 1 gallon of 100% premium gas? Just curious.
Hmmm never thought of that before. I use reg in one car, mid grade in another, and premium/non-oxy for the lawn mower and small engines. I buy 5 gal at a time though so not such a big deal.
@Mike-
Those are hard to find
No doubt. But if you’re riding something with a 2 gallon tank that REQUIRES the higher octane then you have little choice. I can limp on lower but would rather not.
And every time one of those gas stations gets upgraded they go to the 1 hose design. 5 years from now you may not find one.
Sonoco has always had a special “race gas” pump with something like 100 octane dispensed. I used to drive a hobby car that could make it just to the next Sonoco 
What you say could be true. I’ll be forced to deal with it then. Today I can still find one where necessary so no need to take any drastic measures…
Sonoco has always had a special "race gas" pump with something like 100 octane dispensed. I used to drive a hobby car that could make it just to the next Sonoco ;)
There’s a couple of Sunoco’s near me…And they all have just one hose. The only gas stations I see these days with more then one hose are the pumps that also have diesel.
That’s what you get for living in NH!! Try looking in progress averse MA. 3 on way to work that still have the original config.
For those that have motorcycles and are concerned about this, is there an additive at the parts store to compensate? I’ve honestly never had a reason to look, but I’ll bet there is.
Most engines can’t tell the difference between 87 and 92 octane…
Premium Fuel is more about marketing and pool margin than it is about substance or genuine need…But like Tex said, pump the first 1/2 gallon into your car…
Higher than needed octane is not really helpful.Premium is about more than marketing and margin. It detonates less readily that regular, preventing preignition problems ni engines that tend to create more heat in the cylinders due to higher compression in the cylinders. If your owner’s manual requires premium, use premium. If it “recommends” premium, you can safely try four or five tankfuls of both and see if you detect any difference in performance. Preignition can destroy an engine.