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10-06-2009, 07:00 AM | #1 |
Drives: 2001 Yaris T-Sport Join Date: Sep 2009
Location: UK
Posts: 2
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Lower MPG om high octane fuel?
I have the 2002 model 100% standard.
I get 42+ MPG with standard fuel (95ron) driving a mixture of dual carriage ways, traffic jams and blasting it once per journey. Strangely high octane fuel reduces my MPG to 38 on the same mundane journey to work and back! I check my MPG on a fuel calculator and it is accurate to half a decimal place (as long as miles recorded on the trip computer is accurate), so why does high octane fuel reduce efficiency by so much in this engine when it should get better or at worse same MPG? I would have thought being a "sporty" car it would be tuned for high octane feul. |
10-06-2009, 12:06 PM | #2 |
Banned
Drives: '10 Yaris5drHB+99 4runner LTD Join Date: Sep 2009
Location: NE
Posts: 672
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higher octane means less energy per gram of fuel
it only makes more power if: you have higher compression engine that can make use of the (obviously) bigger injectors, higher air/fuel compression pre-spark and pack more air in (bigger intake, forced air induction) or if you have a normal motor, but it is running crappy or has deposits on the cylinder, or for whatever reason the knock sensor is always retarding the ignition...then high octane might make the knock sensor quiet down and you'd get better overall performance. But this is treating a symptom not fixing the root cause High octane fuel in an engine that doesn't need it is a waste of money and you get less mpg all high octane does is, it has less tendency to detonate at the higher compressions, [so you can squeeze the crap out of it and then light it]. Now you get more power and speed, and perhaps the same MPG. but without high comp pistons, and special intake mods (turbo-blower) and an ecu designed for it...you will only end up with less power and less mpg with high octane. |
10-27-2009, 11:54 PM | #3 |
Drives: Yaris 3dr Hatch/Black Join Date: Feb 2006
Location: Deep South
Posts: 114
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I've never owned a four-cylinder that actually like 87 octane (USA's lowest). I always end up using 91/93 and always get better power and mileage everytime.
When you drive a manual, you seem to really feel the smaller differences sense you are more attuned to the car's pulse. |
10-28-2009, 11:38 AM | #4 | |
TSport Underdog
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Quote:
RIGHT ON THE MONEY!! EXCELLENT EXPLANATION !! KUDOS!! |
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10-28-2009, 05:05 PM | #5 | |
Banned
Drives: '10 Yaris5drHB+99 4runner LTD Join Date: Sep 2009
Location: NE
Posts: 672
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Quote:
ordinarily use low octane. in a motor designed for 87 and above, (the Toyota VVT-i Yaris motor) and if it is has no maintenance problems, what you state is not possible except with bad gas...which can be a real issue depending on where you get your gas and the tanks they store the bulk in you simply cannot go faster and get better mpg with a hydrocarbon that has less energy content -unless - you boost compression and air Last edited by 127.0.0.1; 10-28-2009 at 08:04 PM. |
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10-28-2009, 10:11 PM | #6 | |
Half a Bubble Off Plumb
Drives: 2009 Yaris Sedan Join Date: Mar 2009
Location: Bristol, Tennessee, USA
Posts: 1,593
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Quote:
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10-28-2009, 10:37 PM | #7 |
Drives: 09 Yaris HB, 08 SR5 Tundra Join Date: Jan 2009
Location: RGV, Texas
Posts: 1,086
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the sheer fact that you track your MPG should tell you not to buy higher octane. it's more expensive which defeats the whole purpose of trying to get good mileage don't you think.
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12-20-2009, 03:00 AM | #8 |
Drives: 240sx want a yaris Join Date: Dec 2009
Location: Buena Park
Posts: 20
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Im just lurking because I want to buy a yaris in the next 1-2 years but... I heard higher octane on cars that are recommended for the low one is bad. Higher octane fuel burns slower and if you use higher octane in a car that is tuned for a lower octane then things can be bad. Well thats what I heard.
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12-20-2009, 07:00 PM | #9 |
Reluctantly Crouched...
Drives: 2008 Yaris HB M/T Join Date: Oct 2008
Location: DFW, TX
Posts: 867
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I ran 93 octane for a couple of months to see the effect, and my mileage was slightly lower during that period. Obviously anecdotal, since I didn't control all of the variables, but it was a long enough test to be fairly sure that I wasn't getting any improvement out of it. Switched back, and mileage went back up by a couple mpg.
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08-08-2013, 10:30 AM | #10 |
#CarFiend-HANZO188
Drives: 2011 Toyota Vios Join Date: Oct 2012
Location: Wintergarden, FL
Posts: 208
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As far as I know the lowest octane we should use for sure is 87 and in the manual it sais to research octane 91 but it just sais.87 octane fuel or higher. Any where passed 93 is just too much IMO.
Regardless, I'm gonna see about one step higher of an octance right above 87 Octane. These vehicles might just be able to take one octance higher. It just can't be below 87 Octane. Remember that! |
08-08-2013, 11:48 AM | #11 |
What I thought I'd do was
Drives: 09 Yaris Sedan Join Date: Aug 2009
Location: Northwest Alabama
Posts: 1,140
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Ol Johan hasn't been online in nearly 4 years, lol. Good ol zombie threads.
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08-08-2013, 07:08 PM | #12 |
Drives: 08 Yaris Sedan Join Date: Oct 2008
Location: California - Bay Area
Posts: 2,773
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The higher the octane the lower the burn rate which is why you need it for high compression motors. Putting high octane in a low compression motor is going to result in incomplete combustion so that means you are not utilizing all the fuel that is getting sprayed into the combustion chamber which results in partially burnt fuel which will result in more carbon build up on the top of the pistons and valves as well as poorer fuel economy. Putting high octane gas in our cars is simply a waste of money.
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08-09-2013, 11:55 AM | #13 |
#CarFiend-HANZO188
Drives: 2011 Toyota Vios Join Date: Oct 2012
Location: Wintergarden, FL
Posts: 208
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I understand but if you were to add a turbo charger to the car the engine stays the same how does that work? Does the engine become a high compression engine?
I wanna know cause also in the manual for our cars its 87 octanenor higger up to 91 octane. @47_Mason_47 right? I usually read but ignore the dates, lol I'm like the Yaris world reviver of dead threads. CLEAR! BUZZZZZZZZZZZZZZZZZZ |
08-09-2013, 02:11 PM | #14 |
ULTIMATE
Drives: 07 Yaris Turbo Join Date: May 2007
Location: Canoga Park, CA
Posts: 14,859
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^ Sort of. Since there is more than one atmosphere of pressure in the cylinder, higher octane will burn more completely without causing detonation.
Higher octane in a stock motor will have no effect at all on power output.
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08-09-2013, 09:24 PM | #15 |
#CarFiend-HANZO188
Drives: 2011 Toyota Vios Join Date: Oct 2012
Location: Wintergarden, FL
Posts: 208
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Well, thats good to know. Getting this car has been one hell of a learning experience.
So mileage stays the same also. Unless its a higher compression engine which the stock VVT-i Engine in the Yaris is not one, mileage and power are not affected and we should use the the minimum of 87 Octane for our cars. Correct? |
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