Last post on Jan 20, 2013 at 1:20 PM
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Engine, Fuel System
#228 of 297 Re: adaptive transmissions... [explorerx4]
May 09, 2006 (5:36 pm)
As a general rule, the gasoline that a car was designed for (and what is specified in the manual) is the fuel that will allow any given engine to deliver both the best mileage and the best power.
In the case of the Focus, there is no surprise that your mileage went into the dumper, Premium fuel simply isn't volatile enough for that engine.
As for your Explorer, unless your engine is heavily carboned up on the inside of the combustion chambers, Premium gasoline shouldn’t make it run smoother at all. In fact, due to the effectively cooler burn that results from high octane fuel and a low compression engine, all you are doing is accelerating the process of carboning up the combustion chambers. Once enough carbon builds up, then "Hot Spots" can occur, and when they do, then you really will need Premium just to keep the engine from running in a constant state of detonation.
#229 of 297 Re: adaptive transmissions... [shipo]
May 09, 2006 (6:21 pm)
i think you explained what happened with the focus and i am not going to put it to the test again. regular is just fine.
with the explorer v8/auto/towing pkg, it seems like the transmission got out of sync with the change in the operaion of the engine. back to regular gas, everything is as was before.
what do you think about switching brands of gas because they have different formulations?
#230 of 297 Re: adaptive transmissions... [explorerx4]
May 09, 2006 (7:38 pm)
While I've never been particularly brand loyal as far as my gasoline is concerned, I have always tryed to stay with the name brand gasolines if for no other reason than they seem to have a higher turn over rate than the smaller Brand X stations. As modern gasoline ages (and unlike wine, aging gasoline ain't for the best), it becomes less stable (as I understand it, I've never researched this aspect of gasoline), and as such less efficient.
Regarding different formulations, logistically speaking I just don't see how one brand can actually sell different gasoline than the next due to refining and transportation issues as well as various efforts at standardization such as the "Top-Tier" gasoline program.
I'm sure this wasn't much help but there you have it. :-/
Jun 15, 2006 (11:22 am)
If you drive a high performance car like a GTO you should not have bought it for the great gas mileage or the ability to run it on the cheapest gas available! I have a Corvette ZO6, the mileage is pretty good for the way I drive it (13 city/26 highway). I wouldn't dream of putting anything but hightest gas in this booger!!! I had a 68' Goat back in the day and it needed the "good stuff" so as not to knock. Fill er' up n' kick er' in the ass!!!
#232 of 297 I got puished for trying
by MrShift@Edmunds HOST
Jun 15, 2006 (1:33 pm)
I ran two tankfuls of premium fuel in my lowly Scion and actually LOWERED my fuel mileage by 2 mpg.
#233 of 297 Re: I got puished for trying [Mr_Shiftright]
Jun 15, 2006 (3:05 pm)
A noble experiment! That having been said, the results were at least semi-predictable.
#234 of 297 Re: I got puished for trying [shipo]
by MrShift@Edmunds HOST
Jun 15, 2006 (3:53 pm)
I don't get it actually. Maybe I drove faster, I dunno.
#235 of 297 Re: I got puished for trying [Mr_Shiftright]
Jun 17, 2006 (5:58 pm)
Does your car recommend premium? If not that can lower your mileage.
#236 of 297 Re: I got puished for trying [smokey75]
Jun 18, 2006 (3:58 am)
Some cars' manual or fuel door sticker stated "require a certain MINIMUM Octane" Does it mean you should use fuel with that Octane or higher, but not lower. For example my VR6 requires min. 91 Octane, I can use 91, 93, or even 94 with no decrease in mileage or performance. In my case, I try all three, not much difference with mileage or performance.
#237 of 297 Re: I got puished for trying [wai]
Jun 18, 2006 (9:30 am)
Some cars' manual or fuel door sticker stated "require a certain MINIMUM Octane" Does it mean you should use fuel with that Octane or higher, but not lower.
The only correct answer here is, "It depends."
If any given engine is optimized for 91 octane but has ignition control electronics that allow it to retard the spark event for more volatile fuels (lower octane) and/or advance the spark event for less volatile fuels (higher octane), then the "Minimum Octane" in the manual might could well be 87. That having been said, that same engine will lose both performance and economy when anything less than 91 is being used.
The flip side of course is when any given engine is optimized for any given octane rating and then a higher octane fuel is used. In this scenario, performance and fuel economy will suffer if the engine isn't able to advance the spark event sufficiently to start the fuel burn early enough. If, however, the engine can advance the timing, economy and power may actually improve slightly, of course, not as much as an engine optimized to burn said higher octane fuel.