Focus Fanatics - View Single Post - anyone using premium gas ?
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Old 01-30-2013, 07:02 PM   #45
frinesi2
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Join Date: Mar 2012
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Quote:
Originally Posted by mishka View Post
Is there any way to get the normal (non-winter) gas? I rarely start driving on a cold engine.
On that note, it takes almost 5 minutes for the engine to warm up in this 25 degree weather. Is it better to drive it cold since i'm not getting any "mpg" while sitting there at 0 mph? Or should I warm it up like I have been doing? I thought that colder engine uses more gas.
Yeah it's not a rotary or from the 1920's. The only requirements for driving are turning the engine on, and putting it in gear. I would disengage the parking brake too, but to each his own. Maybe give it five seconds to get the oil moving around the block if you want.

Quote:
Originally Posted by Roadworthy View Post
Here is an interesting idea:

Those who have a 2012 TI or I think virtually any 2013 that is designated as being able to use E85, I think they are tuned to scale better with higher octanes. E85 from my understanding has a much higher anti-knock rating, hence why people throw it in for race applications. The big requirement for engines to use E85 from what I remember is high pressure (Direct injection) and a tune that can scale the ignition timing higher to take advantage of the higher anti-knock properties, hence more power!
Correct, ethanol has higher anti-knock properties. It has a higher effective octane rating (some quick research shows it is around 94 - 96 [(R+M)/2]) as a result. The difference is energy density. Pure ethanol has an energy density of 77,300 BTU/gal. If you use a 114,000 BTU/gal base fuel (typical for ethanol free summer fuel, some ethanol free winter fuels may reach this level), E85 will only provide 82,805 BTU/gal, which is about a 27% reduction (hence the estimate you see around that E85 reduces fuel economy by about 30%).

So, E85 increases the octane rating but it has less energy. How do you make more power on E85? You use a crap ton of it. You up the injector size and cram it in there. Say goodbye to any fuel economy you may have had in the first place.

I found a pretty awesome paper talking about gasoline and ethanol that pretty much covers all of the topics mentioned in this thread and pretty much every other gas thread. I recommend every give it a read, it's very informative. It is also where I got my data for the reply above.

Changes in Gasoline - The Auto Technician's Guide to Spark Ignition Engine Fuel Quality
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2012 Focus SE Hatch 5spd sport package, Tuxedo Black Metallic
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