BTU in gasoline

[Cheryl in SD]

My dh would like to know if there is a difference in BTUs of energy in today's gas vs. gas from 30-40 years ago? Thanks.

[farminghandyman]

I think there is but I do not have any proof, not sure if it is BTU's or some thing else, but I know it has changed and not for the better,

as many old cars at one time got a fair or good mileage (example my old 69 galaxy, at one time when it was near new, it would get 22 mph, as the years went on (we drove it for 30+ years), the mileage got worst, we started to add some diesel fuel to the gas tank on every fill up 10 to 20% and it would up the mileage to near where it was when we first got it,

[cfabe]

There are two major differences, the first is the octane, when tetraethyl lead was used as an octane booster pump octane was much higher, so engines could be higher compression which typically gets you more power / higher efficency.

The second is the use of 10% ethanol in much of today's gasoline as an oxygenator, ethanol does have a significantly lower btu content than gasoline so you will get somewhat less mpg on 10% eth/90% gasoline than on 100% gasoline.

[Cheryl in SD]

Thanks!

[Iddee]

In the 60's, the octane of regular was 98+..Today it is 83 to 87.
The octane of high test was 100+..Today it is 93 in this area.

Ten gallons of 10% ethanol gas has 9 gallons of gasoline.
It will give you the same mileage as 9 gallons of gasoline without ethanol.