Last post on Jan 20, 2013 at 2:20 PM
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Engine, Fuel System
#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.
#284 of 297 85 octane
by steve_ HOST
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.
#286 of 297 BMW X3 and "regular fuel"
Jan 15, 2013 (1:34 pm)
I have had a stalling and hesitation problems with my 2012 X3 when temperatures dip below - 3 C for nearly a year now. BMW maintains that this is a wide spread problem with this engine and is caused by premium fuel. In their words, BMW designed the award winning engine for a specific type of fuel and without telling BMW the fuel manufacturers changed their formulations and now the engine stalls in cold weather. I live in the Northeast, by the way. Their suggested fix , which did not come by way of a service bulletin by from an email to the service dept from a regional technician based on what he has done with his own vehicle, is to use regular gasoline until it warms up as it is only a problem with winter formulations. They can't explain why not all cars are affected. I have contacted gas manufacturers and have heard from one so far. They would like BMW to explain themselves as their fuel meets TOP TIER requirements. I can't imagine what mileage I can expect nor the possible engine damage over time. Anyone else with this problem?
#287 of 297 Re: BMW X3 and "regular fuel" [43mary]
by Mr_Shiftright HOST
Jan 15, 2013 (5:33 pm)
It seems unlikely to me, although I'm not a trained petroleum engineer, that a fuel would stall a car when cold but leave it to run perfectly when warm. I'd like to know how BMW explains that scientifically, and by what testing they came to the conclusion. My mind's open to it but I suspect that the car's computer, or "map", isn't dialed in quite right and might need a software upgrade IF...IF....in fact, this is a widespread problem and not isolated to a few cars.
Other ideas come to mind---such as a faulty coolant temperature sensor.
#288 of 297 Re: BMW X3 and "regular fuel" [Mr_Shiftright]
Jan 17, 2013 (4:37 am)
it makes sense to use regular gasoline in winter in any car that can accept it, including those for which premium is 'recommended'. (i've done so for decades in 5 or 10 cars, including as recently as this week...)
no matter the formulation, 87 ignites more easily than premium, by definition.
so if BMW recommends 87 as the solution, and it works for you, then i don't see any issue. happy motoring!
#289 of 297 Re: BMW X3 and "regular fuel" [elias]
Jan 17, 2013 (7:41 am)
Thanks for providing your experience with 87.
It's one thing to use this gas by choice quite another when it is required to get your new engine to start when temperatures dip slightly below freezing. I did not expect a seasonal vehicle.
BMW is not referring to octane but so called changes to the premium fuel additives by manufacturers "after they designed the engine" forcing BMW to "rush to catch up" according to my dealership. No specific manufacturer is mentioned so I'm currently contacting all. So far the response has been that BMW's claim is senseless and BMW has never contacted them. They ask that BMW to do so as gasoline is highly regulated.
If BMW recommends this fuel, let them formalize it in a service bulletin and change their literature re their recommendation of premium fuel for mileage, performance and engine maintenance.
#290 of 297 Re: BMW X3 and "regular fuel" [43mary]
by Mr_Shiftright HOST
Jan 17, 2013 (8:34 am)
Well no arguing if something actually solves the problem, but I'll believe it when I see it---that fuel alone can cure a stubborn stalling problem so reliably that every other cause could be eliminated. ( see below for what I mean)
As for 'burning faster', I don't think this is inherent in the 87 fuel---what I think might happen is that the regular fuel will signal the car's computer to retard the ignition timing (giving you less power and performance by the way), and thus, ignition might occur a bit sooner---so in THAT sense it burns, not faster, but sooner, in the combustion chamber.
On the other hand, any fuel with ethanol would burn FASTER.
My two cents.