My last two tanks of fuel yielded fewer miles than any since I moved here and I was trying to figure out why mileage was back to what I was getting in Texas. When I filled this morning I noticed they have now added 10% ethanol to all pump gas. Station attendant says this is now the standard in OR and WA.

This 10% is the same as it was in Texas, but at least there you got a 93 octane blend. My mileage is down almost 10% now, just like it was before I moved.

Gasoline with 10% ethanol has 97% of the energy content but for some reason it always gives me about 91% of the miles.

Anyone else noticed the change?

 

Oregon has the worst quality fuel of the 48 ajoining states, which doesn't help. and it's oxidated for winter which gives even worse mileage...sorry!

 

I remember hearing one tech at the toyota dealership here say something along the lines of Oregon getting the "leftovers" from other states so the quality is lower.
Not sure how true it was or not.

ALSO, colder here?
colder -> denser air -> more combustion, more fuel?
If I have my logic right...

 

I don't know about the quality part, but in winter they up the ethanol to 10%. I'm not sure when it actually happens, but my guess is two fill-ups ago

 

^ we do have worst quality in the 48 states


Maybe less traffic so you're driving way faster

 

I'm trying to dig up an old link I have back from the the late 90's. Pretty much states the OR does have one of the worst gas quality because there's still no Q/A process for gas stations sanctioned by the government. Therefore, gas station owners can do whatever they want to the gas they buy to increase the volume.

Back then, there was also an independent research group that did their own tests in Oregon, and test results showed Chevron having the best quality overall, I took it with a grain of salt, but I've been sticking to them ever since and have not had gas quality related issues.

 

Oregon has crappy gas admittedly so best bet is to fill only at chevron so it is consistent and also less worries down the road

 

I confirmed what I suspected, it is the change to add Ethanol. This fuel was purchased in Washington although the same thing is being phased in in Oregon. You will get E10 from now on which will result in a drop in mileage of at least 3% but probably 6 - 9%.