Mixing fuel grades

Say (for the sake of argument) that my car needs higher octane than the 87 that comes out of the regular pump… but the local gas station markets 89 for +$.20 and 93 for +$.30 (this is true). Does it make sense to buy 1/2 of 87 and 1/2 a tank of 93? do i get the equivalent of 90 octane out of that? or do i just get an 87 knock every other stroke? or 1/2 a knock every stroke? or is there an 87 gas molecule that is fundamentally different than the 93 molecule and it knocks away and takes the 93 molecules along for the ride? (and mixing gas is just a complete waste with no benefit at all)

Mixing fuels will indeed produce an octane that is between the two. Sunoco used to have blending pumps that pumped the gasoline from two tanks. One tank was the lowest octane and the other was the highest octane. If you set the pump for the lowest octane, the gasoline came from the low octane tank. If you set the pump for the highest octane, the gasoline came from the high octane tank. The other settings would blend the gasoline from both tanks in a proportion to give a specified octane.

Years ago, my dad had a 1963 Studebaker Lark with the V-8 engine. The compression was right on the margin for using regular fuel. If the engine would have a spark knock, we would run the tank to about half full, and then fill with premium to get rid of the detonation.

That’s exactly how most gas stations around here work. Most have only two pumps (87 and 93). To get 89 it’s blended to the right ratio.

You can do that and it should be alright.

The mixing works well for gasoline, but not for beer. If you mix a Michelob with a Busch in a 50-50 ratio, you don’t get a Budweiser.

Seems like an awful of trouble to go through to save a buck. But there’s not reason why it wouldn’t work.

You get Michel lobbed into a bush.

If you can not detect any knock or ping with 87 octane, save your money and use that grade…