Winter gas? MPG Drop
 

I've been filling up at the same gas station (safeway) since I've purchased the car. On the 17th I installed a K&N filter and noticed a nice gain in mpg. (25 to 28 mpg gain).

I filled up today and now I'm back to 25 again, my driving habits have not changed so I was wondering if the winter crap gas is back in the pumps now.

Winter gas = less mpg for the same price. Anyone else noticing this or did I just have a bad week? :bs:

You know, now that you mention it, I've gone from 30-33mpg to 26mpg in the last two tanks. It's kind of disheartening when you can't even get 300 miles to a tank before the gas light comes on, with no hooning involved whatsoever :bs:

To get less then 300 mi per tank you'd have to be getting less then 22.72mi/gal. I hope there's hooning involved. lol

But this is the only car I own that gets above 20mpg. So I'm happy with it... even if I get 22.7 a gal

Which is why I said "can't get 300 miles before the gas light comes on", meaning that I can still go, but should stop to refuel in the next 30 or 40 miles or so. And no, very little hooning. :\

Hmm, well I'm not complaining really. I had a dodge stratus before this car and it got like 19-25 on a good day.

I know there are alot of variables that effect mpg; temp, air pressure, road surface, traffic etc...so to get 25mpg in the one of the worst known cities for traffic is pretty good..

I am curious regarding just what makes winter gas crap?

I think they put something in it to keep it from freezing

It isn't a freezing concern, they "oxygenate" the fuel to reduce emissions during Winter months since the cold environment typically makes haze/pollution worse. The most common way to oxygenate the fuel is by adding alcohol based substances.

The loss of mileage will most certainly be more noticeable on a high compression motor such as in the 86 platform. My Audi S4 (also about 12.5:1 CR) takes a 20% hit on Winter gas, easily. It isn't too noticeable in my Nissan Xterra (about 8.5:1 CR).

But on that note however, typically they don't start shipping winter gas until late October....so although it is certainly possible, you could be experiencing something else like the ECU working out long-term fuel trims as the motor breaks in; or simply compensating for changing air temps as the summer cools off. All FI motors tend to consume a little bit more fuel as air temps drop.

I recently noticed a slight decline in my fuel economy too but I have been attributing it to the school year starting and my commute getting slowed down by buses and 17-18 year old kids who feel the need to drive to school. Even if you don't see the buses it doesn't mean they aren't slowing you down. Obviously this really depends on the times you drive at.

I think you are thinking of reformulated gaoline.
http://www.epa.gov/mtbe/gas.htm

http://www.epa.gov/otaq/regs/fuels/420b03003.pdf


from: http://www.epa.gov/otaq/f99040.pdf
"...
Performance and Fuel Economy
EPA conducted a fleet testing program in 1998 to evaluate car and truck
performance with Phase II RFG, compared to Phase I RFG. Testing took
place in Boston, Chicago, and Houston. The test fleet drove over one
million miles with Phase II RFG. Performance testing was also conducted
in 1998 with utility, lawn, and garden equipment, and with
motorcycles and marine engines. In addition, EPA sponsored fuel
economy testing with Phase II RFG, compared to Phase I RFG.
All available data indicate that no difference in car or truck performance
or fuel economy is expected when Phase II RFG replaces Phase I RFG.
In addition, no difference in performance is expected with utility, lawn,
and garden equipment, or with marine engines or motorcycles.
3
Note that changing from conventional gasoline to RFG, which is oxygenated,
results in a one to three percent fuel economy loss; that is less
than one mile per gallon for a vehicle that gets 25 miles per gallon.
However, there is no additional oxygenate in Phase II RFG compared to
Phase I, so there is no additional fuel economy loss......"


But this would be very much dependant on where you are located. Your summer gasoline may also fall into the category of reformulated, so the winter version may not have more oxygenate.


Some oxygenate might also be added by some marketers for managing water/ice from condensation, like gas line anti-freeze. Although there is unlikely a need for that if there is already some there depending on what type is used.

However they do add more butane in winter which increases the front end volitility to make the fuel vapourize and allow better cold starting. But that isn't anything new, thats been going on since gasoline was a little boy.

http://auto.howstuffworks.com/fuel-e...mmer-fuel1.htm

Depending on how you read this article and it appears to depend on what you consider the norm? Is summer gas just low RVP(vapour pressure) winter gas or winter gas high RVP summer gas. Either way gasoline is adjusted seasonally to make it work appropriately relative the season's operational(and other) requirements relative to engines.

The only time you usually have problems related to seasonal adustment of RVP for gasoline is if you have a really hot day in the spring before the conversion takes place, potential for vapour lock. Or a really cold day before the fall conversion starts which might impact startup or cold idle quality. Being able to see it as a distinct decrease in fuel economy would probably require a substantial mismatch.

But that is normally all managed as well as regional historical temperatures records can predict!

I was curious about the crappy designation? Whether the seasonal adjustments make the gasoline crappy would appear to be more a judgement than a reflection of whether it serves the purpose for the design specifications(whatever those might be, driven for whatever reasons) based on seasonal requirements.

From my own experience I find that the fuel economy of this car varies by really quite a bit depending on how you drive it. The more city driving the worse it is. The more heavy throttle the worse it is. A few spirited accelerations can noticibly affect the average. The longer you stay in lower gears the worse it is. I have varied from 28 to 41 mpg between two tanks(one day apart) just based on the type and place of driving, so it doesn't take much to create a big difference.

BTW we shouldn't forget that its also not unusual to have worse fuel economy in winter just because its colder and takes longer for everything to warm up.

iv gone 350 on full tank.. 95% highway at 55 mph

It could also be the colder weather...

I drive a gas tanker for a living in upstate new york, near Albany.
I have also noticed an unwarranted drop off in mpg. After seeing this tread I decided to check today.
Not all terminals have switched but I noticed that one had switched to the winter blend.
So depending on where you live and what brand you buy, it could be winter blend.
Reformulated is typically used around urban areas like nyc and the surrounding area.