2nd tank of gas with Chevron Techron 87-octane: huge hit on the fuel economy

Thanks for the information - I learnt something new.

It would be then interesting to know, how much a full tank of gas in winter vs. summer changes in terms of volume and energy density. From that we could easily calculate how much less "usable" fuel (rather energy) there is between the two cases.
I still believe the difference will be outweighed by all the other factors that play a bigger role in fuel consumption reduction in winter.

The Wiki article seems to be a bit old though. Modern cars have all injectors and fuel pumps have multiple lines connected to the gas tank to avoid having "air" in the circuit. I wouldn't be surprised if also a small expansion chamber is inside in the engine bay, to avoid bubbles going to the injectors.

 

Yes, that is just one of many factors. Wet roads alone should be worse.

As for that fuel calculation, as long as the ethanol fraction remains constant, simply knowing its volumetric density should be sufficiently accurate, at least to a first order.

Not all the vehicles on the road are modern. And I don't believe that multiple-line fuel systems are sufficiently widespread in the current fuel-injected fleet still in widespread use, to ignore those that aren't.

A much larger fraction of non-road engines, especially small ones, are still carbureted but purchasing the same fuel.

And the EPA evaporative emissions requirements are quite separate from the carburetors vs fuel injectors issue.

 

IIRC, higher octane values refer to the ability to withstand higher compression ratios without pre-detonation (knock,ping, etc). Using higher octane than specified provides no additional benefit, ergo: a waste of money.

Conversely, I was running on fumes with a high performance boat and the only dockside pump within miles had low octane fuel. Not only was it very difficult to re-start and lacked sufficient power to get the boat on plane, but was almost impossible to stop (on a car you can just put it into gear to force a stall, not so on a boat).

 

The Reformulated Gasoline pretty much reduces any minor MPG differences between grades you might see in non-RFG areas outside of Ca. Octane is not the MPG predictor, so much as energy content/density and ethanol. I'd be surprised if the Ca. dealer is allowed to use non-RFG but if so yes that could help MPG.

 

Not to mention WHY they’d go looking for such gas.

 

The cold weather gasoline here sucks. Drops my mpg 3 to 4 gallons.

 

Yes conceivably Japan fuel is indeed very good MPG (no wonder they like Prius so much!!).
USA's reformulated gasoline basically takes a lot of energy/MPG out, no doubt about it.
Not only does reformulated gasoline take energy out of gasoline, it outlaws the oil cos. from transferring the energetic part of the fuel to non-RFG areas, so we are sort of screwed all around, except perhaps say a small independent refinery outside of RFG might be able to sell a more energetic gasoline + E0.

 

I have a hunch the car comes from factory with less than half a tank, just enough for maneuvers during transport plus a bit more for insurance. Dealerships seem to typically fill the tank, say during PDI, but I’d think they just run it over to whatever gas station’s convenient to them.

 

Canada probably has better MPG too without the USA RFG rules.
Possibly we have the lowest MPG here of any Country,.

 

I think ethanol content can vary, for sure. I typically fill up at Chevron. There’s 3 octane options that say “may contain up to 10% ethanol”, and a fourth, higher octane, saying ethanol-free or words to that effect.

Shell i noticed, has 3 octanes, that spec 10, 5 and 0 percent ethanol, going from low to high. I’d guess the regular is 10% ethanol, the highest 0%, and the mid-octane a 50/50 blend.

 

It's not just ethanol that reduces energy here...also the more energetic aromatics levels are regulated here, so you could get a double whammy of better MPG with E0.

 

The U.S. has always been first to apply "realistic" adjustments to account for the common real world driving behaviors and conditions that drag down MPGs. Canada takes a bit longer. Europe even longer, if they ever do it at all.