Last post on Jan 20, 2013 at 2:20 PM
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Engine, Fuel System
#276 of 297 Re: Alcohol [imidazol97]
Feb 25, 2008 (5:25 am)
Missouri has required 10% Ethanol in all grades since January 2008, although some gas stations were offering it in at least one grade a couple of years before the mandate kicked it. I've seen a noticeable (~3 MPG) drop in mileage on my 2004 Isuzu Axiom since then. So I'm wondering if direct injection engines are more sensitive to E10 than other engine types.
#277 of 297 Re: Alcohol [midmoaxiom]
Jun 16, 2008 (2:20 pm)
Sorry to change the conversation, however my casual reading tells me that Ethanol in all grades is the least efficient bio-fuel thus far tested, and is in direct competition with humans for a ready available food source. Ethanol as fuel source should be removed our Lexicon. One day we all will regret the use of corn in this way.
#279 of 297 Re: Alcohol [wtfchuck]
Jun 29, 2008 (6:41 am)
I quit reading that dissertation after a couiple of paragraphs due to incorrect language and incorrect information.
#280 of 297 2002 to 2006 Acura MDX - regular gas ok?
Sep 22, 2009 (2:13 pm)
I believe Acura recommeds premium gasoline for the MDX.
However, I would like to use regular gasoline.
I need feedback form other owners who are doing this or may haev done this in the past. Any degradation in engine performance or pinging?
#281 of 297 Re: 2002 to 2006 Acura MDX - regular gas ok? [vrm]
Sep 22, 2009 (4:52 pm)
While it is unlikely that your engine will ping, it fairly certain that both performance and fuel economy will suffer. Long story short, it will cost you less to use premium fuel in the car.
#282 of 297 Re: 2002 to 2006 Acura MDX - regular gas ok? [vrm]
May 11, 2010 (8:45 pm)
Ok, what premium gas is is 93(Most cars in this case recommend 91 because of Cali.). Which is a octane number for that grade of gas. So in a nutshell the higher compression of the engine the more likely the fuel is to pre-ignite (burns w/o use of spark plug). Thus we run higher octane, meaning that higher octane resists pre-ignition. So running 87 will case a lack of performance due to the knock sensor. And what that does is senses the pre-igntion happening and retards the timing(Opposite of advancing) Thus causing you to lose horsepower. As far as gas mileage goes, you'll lose some MPG's as well. Hope I was not to confusing. Fell free to ask any questions or if you need me to explain more on something else.
#283 of 297 Re: 2002 to 2006 Acura MDX - regular gas ok? [mbowen1989]
May 12, 2010 (1:15 pm)
"Ok, what premium gas is is 93(Most cars in this case recommend 91 because of Cali.). Which is a octane number for that grade of gas."
The AKI (Anti Knock Index) of fuels sold in the States and Canada (and Mexico too?) is an average of two different Octane ratings (i.e. (RON + MON) / 2), and as such it isn't actually an octane rating in and of itself.
"So in a nutshell the higher compression of the engine the more likely the fuel is to pre-ignite (burns w/o use of spark plug)."
Ummm, no. The AKI rating of a fuel has virtually nothing to do with pre-ignition as there isn't a single car sold anywhere in North America that will experience pre-ignition on any grade of gasoline sold here. Where the AKI does come into play is in preventing detonation or "knocking" (hence the name) under normal operation.
A few definitions to help you out:
- Detonation: Detonation occurrs when small pockets of end gas (i.e. unburnt pockets of air and fuel) exceed some critical temperature and/or pressure (varies by combustion chamber design, combustion chamber condition, air/fuel mixture and fuel grade) and spontaniously combusts before the flame front reaches said pockets. A key point here is that detonation happens long after (relatively speaking) the spark event.
- Pre-ignition: The spontanious combustion of fuel before the spark event. Pre-ignition will never-EVER occur, regardless of the grade of fuel, unless the engine has a serious problem, and should such a problem exist, no grade of fuel will prevent it from happening and almost instantly destroying the engine.
Jun 19, 2012 (4:27 pm)
A journalist would like to speak to someone who fuels up with 85 octane and has experienced engine issues or a weaker performance at lower elevations because of it. If you use or have used 85 octane, and would like to share your story with a reporter, please send your daytime contact info to predmunds.com no later than Wednesday, June 20 at 2 p.m. Pacific/5 p.m. Eastern.