Is there a real need to use premium gas?
Apr 2, 2007 | 12:33 PM
#21
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From: St. Paul, MN
The 1GR-FE says to run on 87 or higher, but 91 for optimum performance. I run 89 in mine (in corn farming regions its cheaper due to 10% ethanol content, while 91 or premium contains little ethanol) becuase its cheapest, but fill up with 87 when its the cheapest. No problems running either one whatsoever. No knock at all, becuase the engine has a knock sensor that takes care of that. You may get better performance running 91 octane, but probably won't be very noticeable. Higher octane burns hotter as well, and from my experience, heat kills. So run the lowest you can get away with with out knocking. If you knock, switch to higher octane immediately.
Apr 2, 2007 | 01:52 PM
#22
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From: Montgomery County, Maryland
Thanks guys. Great answers. Great site.
I'm pulling a trailer about 95% of the time. It's not terribly heavy -- probably around 1,200 gross weight including the trailer. This truck does not have the towing package, but the weight it tows falls well below the bumper towing guidelines in the manual, even though I'm actually using an aftermarket frame hitch.
But - you can definitely feel the trailer back there.
It gets hot here in the summer, and humid. Mid to upper 90s is common. Over 100 can happen too once in a while.
Am I foolish to run 87 octane?
Or should I listen and let the "ping" decide for me.
I'd hate to have to add 10% more to my fuel costs, but I will if I have to.
I'm pulling a trailer about 95% of the time. It's not terribly heavy -- probably around 1,200 gross weight including the trailer. This truck does not have the towing package, but the weight it tows falls well below the bumper towing guidelines in the manual, even though I'm actually using an aftermarket frame hitch.
But - you can definitely feel the trailer back there.
It gets hot here in the summer, and humid. Mid to upper 90s is common. Over 100 can happen too once in a while.
Am I foolish to run 87 octane?
Or should I listen and let the "ping" decide for me.
I'd hate to have to add 10% more to my fuel costs, but I will if I have to.
Apr 2, 2007 | 02:14 PM
#23
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From: Idaho
Try running 89 octane...
Do you have an automatic? If so I would put a trans temp gauge in there... Heat is the #1 killer of autos...
I plan to buy an extra hardline from toyota (the hot side of the hardline attached to the tranny) and splice a temp sender into it, then install it. Which will leave me a perfect almost new hardline to sell to one of you who want to do the same thing.
Do you have an automatic? If so I would put a trans temp gauge in there... Heat is the #1 killer of autos...
I plan to buy an extra hardline from toyota (the hot side of the hardline attached to the tranny) and splice a temp sender into it, then install it. Which will leave me a perfect almost new hardline to sell to one of you who want to do the same thing.
Apr 2, 2007 | 02:28 PM
#24
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The 2006 Tacoma Sepcification calls out 91-octane as the "recommended fuel." I'm not sure what the difference is between "Octane Rating" and "Octane Number" as stated in your manual. Like AH64ID mentioned, the 4.0 seems to run fine off of 87 octane, but you will not make the manufacturer-spec horsepower and torque because the engine has to retard the timing with lower-grade fuel.
Not really, all the octane number really is is a qualitative value describing how much ethanol has been added to the gasoline. Ethanol has a nice cooling effect during combustion by lowering the stoichiometric combustion temperatures for the fuel mixture; this in turn helps your engine's cylinders stay slightly cooler and less prone to ping. Therefore, because the engine is not knocking, designers can go for higher compression ratios as well as more spark advance to make more power. In addition, more ethanol helps raise the flash point of the fuel, so even if the cylinder was at the same temperature as with 87 octane, the fuel is less likely to spontaneously combust in the cylinder before the spark plug ignites it.
I just threw the 90 degrees figure out there, but the general problem is that the hotter the ambient air temperature is the hotter your cylinder will be, making your engine more prone to ping. The hotter the ambient air temperature is, the more you engine will have to retard its timing to prevent ping.
In Tucson, on the really hot days (110 degrees plus) some people I knew had to run higher octane gasoline to reduce spark knock in their engines, even though the manufacturer spec called for 87 octane. Stop-and-go traffic in the desert is viscious on an engine...
Not really, all the octane number really is is a qualitative value describing how much ethanol has been added to the gasoline. Ethanol has a nice cooling effect during combustion by lowering the stoichiometric combustion temperatures for the fuel mixture; this in turn helps your engine's cylinders stay slightly cooler and less prone to ping. Therefore, because the engine is not knocking, designers can go for higher compression ratios as well as more spark advance to make more power. In addition, more ethanol helps raise the flash point of the fuel, so even if the cylinder was at the same temperature as with 87 octane, the fuel is less likely to spontaneously combust in the cylinder before the spark plug ignites it.
I just threw the 90 degrees figure out there, but the general problem is that the hotter the ambient air temperature is the hotter your cylinder will be, making your engine more prone to ping. The hotter the ambient air temperature is, the more you engine will have to retard its timing to prevent ping.
In Tucson, on the really hot days (110 degrees plus) some people I knew had to run higher octane gasoline to reduce spark knock in their engines, even though the manufacturer spec called for 87 octane. Stop-and-go traffic in the desert is viscious on an engine...
http://www.ftc.gov/bcp/conline/pubs/autos/octane.pdf
Octane is a number that indicates resistance to detonation. That's it.
The higher the number, the greater the resistance to detonation. The big old radial engines on airplanes (like the 28 cylinder monster on the Constellation) used to burn 130 octane avgas. You still buy 100LL, which is 100 octane leaded fuel for airplanes.
Pinging is not the same as detonation. It is a pre-detonation condition that can turn into detonation.
Google "Octane rating" and you will find plenty of info.
The short version of octane rating is use what the owners manual recommends. If you have issues with one brand, try another brand.
Buying 91 octane when your ride runs fine on 87 is a waste of money.
Apr 2, 2007 | 04:20 PM
#25
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Joined: Dec 2003
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From: Fort Worth, TX
Excuse me while I beat the dead horse...
Ok, so I'm a little wrong in that right now the most common additive to raise the octane rating of a fuel is not ethanol, but is in fact MTBE (methyl tertiary butyl ether) which is made from methanol. Still, MTBE is being phased out with ethanol because while ethanol is slightly more expensive, MTBE is carcinogenic and readily bonds with water, contamintaing the water table if leaked.
The "Octane rating" of a fuel however is not some magical number pulled out of the air that isn't really based on anything. While it does describe a fuel's resistance to ping, the number comes from a specific measurement and is tied directly to the amount of octane and MTBE/ethanol in the fuel. The Octane reading's original roots come from from early refining of gasoline from crude, when it is made up of heptane and octane. Heptane tends to ignite quite easily, while octane is resistant to it. The early rating was a straight volume percentage of octane vs. heptane, where 87 octane was 87% octane, and 13% heptane. But, additives can artificially increase the octane rating of a fuel with a lower octane percentage, or push the percentage beyond 100% in the case of racing and aircraft fuels.
So you see, the ethanol or MTBE percentage in the fuel has a DIRECT LINK to the fuel's octane rating. Capiche?
A quick read on gasoline additives: LINKY
Originally Posted by HowStuffWorks.com
Gasoline additives
...When lead was banned, gasoline got more expensive because refineries could not boost the octane ratings of cheaper grades any more. Airplanes are still allowed to use leaded gasoline, and octane ratings of 115 are commonly used in super-high-performance piston airplane engines (jet engines burn kerosene, by the way).
Another common additive is MTBE. MTBE is the acronym for methyl tertiary butyl ether, a fairly simple molecule that is created from methanol. Click here to see MTBE's chemical structure.
MTBE gets added to gasoline for two reasons:
...The most likely thing to replace MTBE in gasoline is ethanol -- normal alcohol. It is somewhat more expensive than MTBE, but it is not a cancer threat.
...When lead was banned, gasoline got more expensive because refineries could not boost the octane ratings of cheaper grades any more. Airplanes are still allowed to use leaded gasoline, and octane ratings of 115 are commonly used in super-high-performance piston airplane engines (jet engines burn kerosene, by the way).
Another common additive is MTBE. MTBE is the acronym for methyl tertiary butyl ether, a fairly simple molecule that is created from methanol. Click here to see MTBE's chemical structure.
MTBE gets added to gasoline for two reasons:
- It boosts octane (see this Question of the Day for a discussion of octane).
- It is an oxygenate, meaning that it adds oxygen to the reaction when it burns (see this Question of the Day for a discussion of oxidizers). Ideally, an oxygenate reduces the amount of unburned hydrocarbons and carbon monoxide in the exhaust.
...The most likely thing to replace MTBE in gasoline is ethanol -- normal alcohol. It is somewhat more expensive than MTBE, but it is not a cancer threat.
Last edited by mastacox; Apr 2, 2007 at 04:21 PM.
Apr 2, 2007 | 05:09 PM
#26
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From: Montgomery County, Maryland
What bothers me about 89 octane is it's almost as expensive as 91 octane and 93 octane. It seems to me, if I'm going to buy the good stuff, I may as well get my money's worth.
The manual doesn't talk about a load. My manual just says use 87. Yet the link above says 91 recommended. This is for the 4.0 Litre according to the pressrooom.toyota.com link above.
I'm pulling a load. Does that matter?
Apr 2, 2007 | 07:37 PM
#27
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From: Idaho
No. Didn't want an automatic when pulling a trailer. I have a six speed.
What bothers me about 89 octane is it's almost as expensive as 91 octane and 93 octane. It seems to me, if I'm going to buy the good stuff, I may as well get my money's worth.
The manual doesn't talk about a load. My manual just says use 87. Yet the link above says 91 recommended. This is for the 4.0 Litre according to the pressrooom.toyota.com link above.
I'm pulling a load. Does that matter?
What bothers me about 89 octane is it's almost as expensive as 91 octane and 93 octane. It seems to me, if I'm going to buy the good stuff, I may as well get my money's worth.
The manual doesn't talk about a load. My manual just says use 87. Yet the link above says 91 recommended. This is for the 4.0 Litre according to the pressrooom.toyota.com link above.
I'm pulling a load. Does that matter?
I agree on the 6-speed thing on diesels, but not after all the faults I have read about this 6-speed. and the 5speed auto is such a sweet tranny.
Apr 2, 2007 | 08:01 PM
#28
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All right guys, thanks. I was the guy that started this thread and now I have learned even more. Thanks guys, I will run a few tanks of premium through the 4 runner and see if I still notice that sound. Thanks again!!
Apr 4, 2007 | 09:31 AM
#29
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From: Fort Collins, CO
It seems some people are a little unclear on this...
US Gas pumps don't go by "Research Octane Number" they go by Octane Rating. For the 2007 Tacoma, 87 or higher is recommended that is the SAME as RON91... BUT the 91 at the pump is not RON91, its actually higher. 87=91RON.
Its interesting that people think the V6 will get more power and economy with 89 or 91 octane from the pump. I'll have to try it sometime. Although here in Colorado we only have 85, 87, 91, supposedly because of the altitude you can run 85 as 87, 87 as 89, and 91 as 93. I've run 85 before with no problems at all, but it was also mild weather. I'd never do it when its very cold (dense O2) or very hot (burns hotter than premium or super). Typically I use 87 and have two 20L fuel cans with 91 mounted in the bed most of the time.
US Gas pumps don't go by "Research Octane Number" they go by Octane Rating. For the 2007 Tacoma, 87 or higher is recommended that is the SAME as RON91... BUT the 91 at the pump is not RON91, its actually higher. 87=91RON.
Its interesting that people think the V6 will get more power and economy with 89 or 91 octane from the pump. I'll have to try it sometime. Although here in Colorado we only have 85, 87, 91, supposedly because of the altitude you can run 85 as 87, 87 as 89, and 91 as 93. I've run 85 before with no problems at all, but it was also mild weather. I'd never do it when its very cold (dense O2) or very hot (burns hotter than premium or super). Typically I use 87 and have two 20L fuel cans with 91 mounted in the bed most of the time.
Apr 4, 2007 | 02:47 PM
#30
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From: Montgomery County, Maryland
It seems some people are a little unclear on this...
US Gas pumps don't go by "Research Octane Number" they go by Octane Rating. For the 2007 Tacoma, 87 or higher is recommended that is the SAME as RON91... BUT the 91 at the pump is not RON91, its actually higher. 87=91RON.
US Gas pumps don't go by "Research Octane Number" they go by Octane Rating. For the 2007 Tacoma, 87 or higher is recommended that is the SAME as RON91... BUT the 91 at the pump is not RON91, its actually higher. 87=91RON.
Apr 4, 2007 | 02:51 PM
#31
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Joined: Dec 2003
Posts: 2,893
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From: Fort Worth, TX
It sounds to me like "Research Octane Number" would be the actual measured W% of octane in the gas, while "Octane Rating" would be how the gas performs with the additives. But if this was the case, the RON would be lower than the OR so I'm confused...
Apr 4, 2007 | 04:28 PM
#32
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From: Fort Collins, CO
RON and MON. I'm not exactly sure of the differences, but basically they are just two different tests. RON is usually 8-10 points higher than MON.
In Europe and Japan (not sure about other parts of Asia and I know many parts of Africa having wildly varying types of gas, including leaded...) RON is what is stated on the pump. Not sure about S. America, but I know Brazil runs a lot of cars on 85-100% ethanol.
In the US (and I believe Canada and Mexico) we use "Octane Rating" AKI for Anti Knock Index. It is an average of RON and MON ratings. You'll often see it shown as "R+M/2" which doesn't make any sense when you see it on the pump unless you know about RON and MON and then you'll see its just the average between them.
So basically in the USA we can ignore RON and MON and just go by "Octane Rating" as Toyota calls it in the manual, or (R+M/2) Rating.
Apr 4, 2007 | 06:49 PM
#33
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From: Montgomery County, Maryland
No. There are two different ways of measuring octane (for the most part).
RON and MON. I'm not exactly sure of the differences, but basically they are just two different tests. RON is usually 8-10 points higher than MON.
In Europe and Japan (not sure about other parts of Asia and I know many parts of Africa having wildly varying types of gas, including leaded...) RON is what is stated on the pump. Not sure about S. America, but I know Brazil runs a lot of cars on 85-100% ethanol.
In the US (and I believe Canada and Mexico) we use "Octane Rating" AKI for Anti Knock Index. It is an average of RON and MON ratings. You'll often see it shown as "R+M/2" which doesn't make any sense when you see it on the pump unless you know about RON and MON and then you'll see its just the average between them.
So basically in the USA we can ignore RON and MON and just go by "Octane Rating" as Toyota calls it in the manual, or (R+M/2) Rating.
RON and MON. I'm not exactly sure of the differences, but basically they are just two different tests. RON is usually 8-10 points higher than MON.
In Europe and Japan (not sure about other parts of Asia and I know many parts of Africa having wildly varying types of gas, including leaded...) RON is what is stated on the pump. Not sure about S. America, but I know Brazil runs a lot of cars on 85-100% ethanol.
In the US (and I believe Canada and Mexico) we use "Octane Rating" AKI for Anti Knock Index. It is an average of RON and MON ratings. You'll often see it shown as "R+M/2" which doesn't make any sense when you see it on the pump unless you know about RON and MON and then you'll see its just the average between them.
So basically in the USA we can ignore RON and MON and just go by "Octane Rating" as Toyota calls it in the manual, or (R+M/2) Rating.
Apr 4, 2007 | 07:00 PM
#34
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From: NW Florida
I don't know one person who uses 91+ oct in their 4thGen 4-Runner. I have almost 90k on my mine and have always used 87 w/o any poor results. I used 91 twice, once because it was all I could get (natural disaster) and once to see if I would get MPG or performance, I didn't.
Apr 5, 2007 | 06:16 AM
#35
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From: Fort Collins, CO
Apr 6, 2007 | 12:36 PM
#36
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From: Vancouver, BC, Canada
There is a 'risk' of putting a gas with an octance rating that is too high. Putting gas of a higher octane rating than recommended by the manufacturer may leave deposits in the engine due to incomplete combustion. Like mentioned many times before in this thread, the higher the octane rating, the harder it is to combust the fuel mixture, therefore an engine that was designed to use 87 octane will not be able to efficiently combust gas at a 91 octane rating.
Apr 7, 2007 | 01:43 PM
#37
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From: Fort Collins, CO
There is a 'risk' of putting a gas with an octance rating that is too high. Putting gas of a higher octane rating than recommended by the manufacturer may leave deposits in the engine due to incomplete combustion. Like mentioned many times before in this thread, the higher the octane rating, the harder it is to combust the fuel mixture, therefore an engine that was designed to use 87 octane will not be able to efficiently combust gas at a 91 octane rating.
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