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Discussion Starter #1
Purchased our new scion xb this year - was getting expected mileage before engine breaking in (28 - 30 around town and 30-32 highway.) About 700 miles ago (we now have 6200 miles on it) the mileage suddenly dropped to 25 mpg. It has been exclusively driving around town. Took it into our local Toyota repair shop and we were given a song and dance about poorer mileage in cooler weather (hasn't even been down to low 40's yet) and needing to buy higher octane gasoline (even though our manual recommends regular. Was told they would check it out, but we would probably have to pay for the servicing because if there was a leak, it would show. Any suggestions? Help
 

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Do you have an auto or manual?
 

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Check to see if your gas stations are using ethonol additives.
I've noticed a drop in mine since the local stations started using this.
 

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Gas stations typically start changing over to "winter blend" fuels in September/October. Winter fuel blends get notoriously worse fuel mileage. That, combined with the poorer mileage caused by colder weather could be what you are seeing.

Tomas
 

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Winter Formula Gas.

They add ethanol to keep the water ( yes, there is always a little) from freezing in your fuel line, throttle body( they will actually freeze on the butterfly) and tank/fuelpump.

Ethanol burns at a different rate so to keep same power, you end up using more, hence the drop in mpg.
 

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In addition to that, the blend of petroleum distillates used in winter blends includes a much larger percentage of the more volatile ones, which also have less energy per volume than the more dense, but less volatile distillates used in summer blends. It's not just additional ethanol, but lower energy gasoline in winter blends. The high-volatility is needed for the gas to work properly and form adequate burnable vapors for engine starting in cold weather...

Tomas
 

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I dont know if I believe the stuff above ethanol changes in the gas and all. I mean I know it happens, and its not made up. I know a few of the midwest states have Ethanol blend gas that is 89/90 Octane gas (that is same priced if not cheaper than 87). Ive ran that in my car straight from the dealership. I average 33-35 in town and 30-31 on highway. Its always ran good with great gas mileage on ethanol. Maybe its just the change for you car. I dont believe than ethanol gets you any worse mileage or any of that however, regardless of the scientific stuff behind it. Just my .02. Best of luck pointing out the problem here. Nothing will be definitive.

Scotty
 

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I noticed a slight drop in my MPG as well. Now, since we're forced to live with lower MPG during winter months, gas manufacturers should be forced to lower the gas price to make up for the poorer MPG.
 

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chevoron gas is crappy!....dont use arco,costco,shell is ok...and 76 gas is all that i use...but if there is no 76 around i use shell or if those 2 arent around i'll bite my lip and get cheveron
 

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Discussion Starter #11
crappy mileage

Thanks for all your responses! The winter case scenario sounds pretty much like what I was told at the Toyota service center. Guess I have to bite it, but will at least try a different station for a few fill ups and see if that makes a difference
 

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Heh. The price of gas has never been based on MPG, though that's an interesting idea. :)

Actually winter blends cost a slight bit more to produce since the the more expensive ethanol also adds handling difficulties and the fuel can't be shipped through the pipelines after being diluted with it, so it has to be added at the local distributer just before it is loaded into the delivery trucks.

Add to that the higher volatility (higher vapor pressure) gasoline that needs to be used so cars will start - which are also more expensive - the cost for the poorer winter fuel should be higher.

Instead, of course, they increase the pump price in the summer and especially around holidays when people will be using more...

Gasoline prices aren't really based on cost to produce or quality, but on profit.

(Ever figure out how when the price of a barrel of crude goes up in the Middle East, the 30,000 gallons in the tank that the station has already paid for goes up, too?)

Never mind. That's another discussion.

Tomas
 

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Tomas said:
Heh. The price of gas has never been based on MPG, though that's an interesting idea. :)

Actually winter blends cost a slight bit more to produce since the the more expensive ethanol also adds handling difficulties and the fuel can't be shipped through the pipelines after being diluted with it, so it has to be added at the local distributer just before it is loaded into the delivery trucks.

Add to that the higher volatility (higher vapor pressure) gasoline that needs to be used so cars will start - which are also more expensive - the cost for the poorer winter fuel should be higher.

Instead, of course, they increase the pump price in the summer and especially around holidays when people will be using more...

Gasoline prices aren't really based on cost to produce or quality, but on profit.

(Ever figure out how when the price of a barrel of crude goes up in the Middle East, the 30,000 gallons in the tank that the station has already paid for goes up, too?)

Never mind. That's another discussion.

Tomas
Excellent info Tomas. It's always good to learn how things truly work. Including our gasoline supply.

Does anyone know of a way to get the lost MPG back that's lost in the winter blend? Possibly increase octane (put 89 versus 87 in the tank)?
 

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Damn Tomas.. always some great info to read in your posts!

I was always told to keep the fuel tank over halfway full at all times during the winter months. I think it pertains to preventing the water in the gasoline from freezing up in the tank before even discussing the fuel lines themselves. Maybe consider trying to "break in" the xB with winter gasoline like the beginning break-in period of the car.. just a random idea to add to the thread.
 

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Also remember that as you use full heat, the a/c compressor also is on; another power robber. bne sure you also didn't hit something and throw a setting out.
 

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The A/C is only on (with the A/C switch off) when in any of the 'defrost' positions. (Also, be sure to use outside air and not recirc when in defrost so it works right.)

Tomas
 

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OK, two more. :D

Higher octane fuel won't increase your gas mileage unless what you normally use causes knocking or pinging. The octane rating of gasoline is NOT a reference to the power it contains, but how well it can resist "detonation."

...

To provide smooth power to the vehicle, the gasoline needs to expand in an exponential manner during the entire down stroke of the piston during it's power stroke.

That means the gasoline needs to burn in a controlled manner rather than exploding and delivering all of it's power in a flash.

If the engine is under a high load and the cylinder pressure increases to the point that the fuel explodes instead of burning, you have ping. That "ping" sound is that explosion of the fuel causing the piston to descend rapidly enough that the connecting rod bearing penetrates the oil barrier and makes metal-to-metal contact. "Ping!"

However, if the gasoline explodes because of the residual heat in the cylinder while being compressed, that is knock.

Both ping and knock indicate the fuel's octane rating is too low for operating conditions. The higher the compression ratio the more likely that detonation (knock or ping) is to happen.

Higher performance engines traditionally have higher compression ratios so they can get more power from the same displacement.

To prevent the gasoline from detonating (exploding) instead of burning, the octane of the blend needed is increased.

Since higher compression engines produce more power for the same displacement than low compression engines, and since higher compression ratios make detonation more likely to happen, the high output, high compression engines use high octane fuel.

Since the high output engines use high octane fuel, it has become associated in people's minds that the higher octane fuel provides more power.

This is not true. Higher octane just makes it harder for the fuel to explode instead of burn, and has NOTHING to do with how much energy there is in the fuel.

(Some modern engines that control their engine's advance with input from a "knock sensor" CAN pull slightly more power from a high octane fuel while under full load, since the controller doesn't retard the timing quite as much at maximum load. For normal driving this usually isn't noticeable, and will not increase gas mileage.)

OK, Second item. :)

The purpose of keeping the tank more full in winter is to reduce the amount of damp, cold air in the tank, which reduces the amount of water that condenses out of the air in the tank overnight. This reduces the water contamination of the fuel.

(A secondary reason does not apply to our cars since they are front drive. In typical rear-drive cars with gas tanks mounted in the rear, the additional weight of a nearly full tank can often increase traction in snow.)

Now I'm tired of typing, and will shut up for a while. :D

Tomas
 
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