why lower octane at higher altitude

Athletes performing at higher altitudes know that the altitude affects their performance, especially their endurance, since high altitude (HA) causes faster and deeper breathing. Ran it for years when I lived there, and still run it when I visit family now. Why do cars overheat at high altitude? Some high elevation locations, like Colorado for instance, sell fuel with an octane rating as low as 85. I'm quite sure Jason of Engineering Explained knows all of this but likely would put his channel in jeopardy for being censored or restricted if he espoused anything other that the . Onwers manual won't have anything. They burn slower than low octane fuels. Altitude definirely makes a difference as far as octane is concirned. High octane fuels aren't denser than lower octane fuels. Research several years ago from the American Petroleum Institute showed that lower air pressure at higher altitudes allows vehicles to perform as well with 85 octane as they would with 87 at lower. Misspeabodi Ok that makes sense, thanks for the easy to understand answer. At higher altitudes, the thinner air compensates for the gasoline's lower octane, so the engine can usually run without detonation. That's why the octane ratings at the gas stations at high altitude are lower than at sea level. The octane rating is in fact noticeably lower, which can lead to performance problems at lower altitudes. I thought that one can and should use a lower octane at higher altitudes but I also know if most cases the manual "wins". A minimum of 87 octane/87 AKI (91 RON); If operating at high altitude, see below. The easiest way is to raise the compression ratio. If I lived at lower elevations, I would definitely run premium fuel. Does elevation affect engine performance? It will also briefly cover the symptoms of high cortisol and both low and high aldosterone. While maintaining the same boost level at lower altitudes, Levine noted, other limits can be encountered, like turbo speeds at higher rpms that could also result in a power reduction (at higher . A higher octane number means that the fuel-and-air mixture can withstand more compression before detonating. Hi all: I live at 5000+ ft above sea level. In the US, you may see this above 4000 ft altitude. 5.7 Hemi. The higher elevations have a lower level of air pressure, which means an engine needs less octane to properly fire due to the lower ambient pressure. At that altitude, they were almost . It was very hot out (113 IIRC), and the engine was pinging on it very badly, had to run 3rd gear, 4th at the highest and only when I was on the level. Furthermore the manual states fuel additives are not to be used. regular, mid-grade or premium. The difference in prices between premium and lower octane grades has also increased.As a result, more people are curious about what octane is and what those octane rating numbers on gas pumps mean. I don't know how, but I found a Sunoco gas station which sells 110 octane racing fuelfor only $7. Is it OK to use premium gas in a lawn mower? If you put this lower octane in your vehicle and then drive to lower elevations, your check engine light may come on. I think at higher altitudes lower octane becomes more potent, or something like that. The octane has to do with compression in the cylinder, so when the intake air has less pressure there is less air (molecules) taken in for combustion. Otherwise use the 87 mid-grade. When that occurs, bubbles begin to form and the water boils.When atmospheric pressure is lower, such as at a higher altitude, it takes less energy to bring water to the boiling point. The air pressure at sea level is 14.7 pounds per square inch, but in Denver Co, 1 mile above sea level, it is only 12 psi. Also, why is air denser at lower level than at higher altitudes? OCTANE is simply a rep for anti combustion. Assuming your jetting is close or dead on, at high altitude, do you still run the high octane pump gas, or is lower octane help running at such high altitude. This suggests a lower octane will work in high altitudes. If you are staying in the area, you can generally use the same level of gasoline you would at lower altitudes , i.e. Either way, using an octane 2 points lower would make the car a little less peppy and maybe hurt fuel economy a little bit. Thanks for any input. I think living in CO and higher elevations >4000 ft make it easier to run a lower octane because the air is less dense up here. • Higher mixes of ethanol. The group of Luftwaffe Bf-109 fighters passed high above the English channel at 38,000 feet. … There's no need to run a small lawnmower engine on high-octane gas, but it won't hurt your lawnmower, either. Your static compression ratio will be lowered by the lower lower atmospheric pressure and therefore detonated will less problematic, lower octane fuel burns faster and therefore will net higher hp. A: At higher altitudes, the air is thinner so you can actually get by with a lower octane gasoline. Most gas stations in the US offer gas at octane . You don't need higher octane in high altitude. So those that say you can use 87 with or without an octane booster are in direct opposition to what the maker of the engine says. I have heard that with the higher altitude and thinner air that you can use a lower octane gas and the cars run just fine. What is octane? Air is thinner. Less Octane = Easier to burn, less energy spent, more power. Less energy means less heat, which means water will boil at a lower temperature at a higher altitude. Why is lower octane fuel sold in higher altitudes? For instance, regular grade fuel is 87 octane in Chicago, but 85 octane in Denver. If your car doesn't like it, then step up. This means the air has less oxygen per cubic foot than air at sea level; the air/fuel ratio will become richer and that will act like a high-octane fuel. It is not very wise to use 87% octane fuel for an altitude over 6000 feet just simply because the atospheric presure varies & is thicker, making travel more intense. Higher altitudes require lower octane. In the U.S., unleaded gasoline typically has octane ratings of 87 (regular), 88-90 (midgrade), and 91-94 (premium). In most of the rest of the country, regular is 87 octane. Owners manual says to use 89 octane, but would that be applicable at 5k-6k above sea level? Your car will adjust itself for any elevation. Taking the 0.2 number, your Tundra would do just fine with 86 octane fuel at Denver and would only need 85 octane at 10,000 ft. Craig. Unless EVERY car is driven at high altitude no manufacturer is going to specify anything lower than 85 octane. The way I figure, 87 should be ok as its mid grade out here. Low-octane fuel — rated 85 or 86 as opposed to the 87 for regular gasoline — is common in the Rocky Mountain states, said General . Piston-powered aircraft most commonly use 100 octane low-leaded fuel and fly at altitudes below 15,000 feet. So, take the same sled, lean it down, and run 91 octane and the power will be the same as stock calibration with lower octane fuel (maybe even a tad better). It can have a small effect around 1000' - 1400'. • Lower-than-expected octane. I used to live in a lower altitiude area where the low grade gas was 87 octane, but I moved to a high altitiude area (4,000 feet) and the low grade gas here is only 85 octane. Apr 1, 2017. So, it's OK to use lower octane fuel than recommended at high altitudes. It will help with getting your car to play nice with the new grade of fuel and thinner air. I would say it's a good thing to run by your mechanic next time you . mark888 said: Mainly because barometric pressure is normally lower at altitude, so vehicles can perform as well with 85 octane as they would with 87 at lower altitudes, thereby saving money. Looks like you guys have even lower octane at 85 although you are at a lower altitude than where I am (~7000 ft)! I have done some research on the subject but . The issue: Regular-grade gasoline in Colorado is 85 octane. 2 days ago Onwers manual won't have anything. Engine. You may have noticed on your last vacation to the beach that it's a bit hard to breathe in Colorado. Wait. 2 Stroke Octane / Altitude. However, "premium" (high octane) gas in high altitude areas often has a lower octane rating than "premium" sold in low-altitude areas. According to this article from AAA, the stated reason is that most of Colorado is at high elevation, above 5000 feet (about 1500 meters), and the thinner air tends to prevent detonation. They also have more resistance to detonation caused by extreme combustion chamber temperature and pressure. If turbocharged, stick to manufacturer recommendations. A: At higher altitudes, the air is thinner so you can actually get by with a lower octane gasoline. You'll typically see lower octane gasoline offered for sale at high altitude because higher octane doesn't offer as much advantage. Looks like you guys have even lower octane at 85 although you are at a lower altitude than where I am (~7000 ft)! It's a swapped 91 civic with a motor that came from overseas. XDM45 likes this. Higher Altitude Means Less Power. #1 So a few weeks ago on the show a caller from Denver asked about using a lower fuel octane at altitude and the answer was there is no harm since the compression in the chamber is lower with the thinner air you can use a lower octane. #7. You don't need as much octane at higher altitudes. But then I wasn't sure why the octane is 86 instead of the standard 87 until I read about the altitude's effects on compression. Premature detonation can result in an engine making knocking, pinging or rattling sounds. It's easy to forget that we are at a pretty high altitude here in Boulder. So we are are familiar with our 2 strokes jetting, I am riding a few different area from low elevation to high elevation as high as 10k-13k feet. Why Running a Lower Octane at High Altitude is Recommended. Does altitude affect octane rating? Premium gas, such as 93 octane, helps high-powered cars run smoothly and efficiently. Since you have come up to a higher altitude, there is a lower atmospheric air pressure, less air entering the engine, so the temperature at TDC drops, therefore, you can use a lower octane fuel. Your car will adjust itself for any elevation. If I lived at lower elevations, I would definitely run premium fuel. At higher altitude the octane required is usually lower that is why your regular grade is 85 instead of the more common 87. . People vary in the However, here in the Mile High City, 85 octane gas works great in most cars. The Pressure Impact from Higher to Lower Altitudes. 2 Stroke Octane / Altitude. At higher altitudes, the thinner air compensates for the gasoline's lower octane, so the engine can usually run without detonation. Higher elevations mean engines need less octane in the fuel to properly start running. In recent years, car manufacturers have been requiring or recommending premium gasoline (a high-octane grade of fuel) for use in more of their vehicle models. Plus, you can run a lower octane gas. This is one reason why gas station fuels available during winter months, or at higher altitude locations, may have lower octane ratings compared to stations in warmer or at lower altitudes. Looking at it, it is pretty clear why 85-octane became an option at higher altitudes. regular, mid-grade or premium. This graph was from a large study in 1942 regarding the difference in octane number requirements as altitude changes. "If I put 85 octane in my cars, they just knock like . If you have a high com, ( (pression engine, depending on how High, (110 is for the highest compression) it would be better. The nationwide average for 87 octane is $2.36. _____ Colin Chapman disciple 05-15-2006, 07:01 PM . How High-Octane Gasoline Saved Untold Allied Pilots During WWII. But running a little higher octane does not hurt. • Lower-than-expected octane. So, octane ratings can be reduced with lower ambient temperatures and pressures on normally aspirated engines. If your engine has high enough compression to require, and run lower octane the ECU and sensors will reduce the timing accordingly, it may cost you 10-30hp that you are not using anyway unless you a a jumper i the 200s or at high altitude. When I went through Death Valley, (very low altitude) I was still running the low grade stuff, which was all I could find, on my K75S. Gasoline with an octane rating of 85 is available in . In a low compression engine, you'll probably go slower using it. We have customers who run 14:1 with 91 octane gas at higher altitudes. Probably. High octane fuel, therefore, helps reduce or eliminate knocking, pinging or rattling in engines. Therefore, in theory, one can use the cheaper, lower octane fuel without problems, and save some money. Posts. As long as you don't experience knocking or pinging it will be fine. I doubt it would do any serious damage. 2014. If you are staying in the area, you can generally use the same level of gasoline you would at lower altitudes , i.e. 85 octane works fine in most normally aspirated engines, fuel injection or carb, at higher altitudes. Octane is a measure of the fuel's ability to resist detonation, nothing more. Higher altitude will richen the air/fuel mixture because atmospheric pressure drops as you go up in elevation. The altitude effect on an engine is a gradual condition. So, at higher altitudes air molecules can spread out more and air density decreases. 93 will show up in a day or so. For instance, regular grade fuel is 87 octane in Chicago, but 85 octane in Denver. Relocating to Denver from central FL and noticed they have lower octane available at the pump. It's why diesels are so popular at altitude. A: At higher altitudes, the air is thinner so you can actually get by with a lower octane gasoline. I ran a very hopped up MOPAR 340 on 91 octane a few years back in Colorado Springs, but had to put octane booster in at lower altitudes in California on the same octane level gas. This is why you only find 91 instead of 93 in areas at higher altitude. This is more important to motorcyclists because bikes have smaller fuel tanks and a lower tolerance for low-octane gas compared with most cars. The obverse of that is that lower-compression engines can run on lower-octane gas. Share Improve this answer I don't think would run 85 octane in my '05 V8 because I don't want the engine detonating at high rpm even if the computer can control it or not. So that got me to thinking if using a higher octane fuel than recommended is actually worse for the car. I don't think would run 85 octane in my '05 V8 because I don't want the engine detonating at high rpm even if the computer can control it or not. Many people say that because of the higher altitude and less air pressure, most cars will run well with a lower octane gasoline. However, those graphs no longer hold true for more modern cars. It is also true premium fuel is called premium not really due to its octane rating, but because it is of much higher quality. regular, mid-grade or premium. It is for this reason that in most parts of Colorado "regular" gas is rated 85 octane instead of the . A: At higher altitudes, the air is thinner so you can actually get by with a lower octane gasoline. In certain states, such as Colorado where the altitude is generally above 5,000 feet in the mountain regions, 85 octane gasoline is sold, while in lower elevations 87 octane is the lowest sold. So we are are familiar with our 2 strokes jetting, I am riding a few different area from low elevation to high elevation as high as 10k-13k feet. For instance, regular grade fuel is 87 octane in Chicago, but 85 octane in Denver. If you have ever driven from a high altitude, say 5000' above sea level to about 1000', and you have a flexible sealed empty bottle in the car, at some point, you notice the creaking sound as the bottle collapses due to lower atmospheric pressure sealed inside and higher atmospheric . But I didn't know that about 91 being acceptable bc of higher elevation. The number fluctuated between a 0.2 and 0.5 reduction per thousand feet gained in elevation. A higher octane number fuel does not give you more power unless the engine is . Avgas is either 80 octane mogas or 100 octane low lead. B. Simply put, less oxygen in the air, correspondingly lower need for octane. For instance, regular grade fuel is 87 octane in Chicago, but 85 octane in Denver. If your manufacturer requires regular fuel, which is normally 87 octane in the US, then you can use the 86 octane regular fuel when you are in Albuquerque at 6000 feet. Try it as it should work. The idea that the ECU can adjust for low octane is not entirely true, because detonation from pressure has nothing to do with ignition timing. In certain states, such as Colorado where the altitude is generally above 5,000 feet in the mountain regions, 85 octane gasoline is sold, while in lower elevations 87 octane is the lowest sold. The higher elevations have a lower level of air pressure, which means an engine needs less octane to properly fire due to the lower ambient pressure. At lower altitudes, typically 10,000m, the turbine engine can generate up to 5 times higher power density than the reciprocating engine, as long as inlet air mass flow is adequate. Given what you said, does that mean I have a . All of that said, the general theme in this thread is correct; that at higher altitudes, cylinder temperatures (and hence pressure) will be lower and the required octane to prevent engine damage is reduced. Low-octane fuel — rated 85 or 86 as opposed to the 87 for regular gasoline — is common in the Rocky Mountain states, said General . And from 2500' and up you must find some way to offset the pressure loss. This is not true for modern gasoline engines. My manual for my 2015 Corolla specifies 87 octane and has no comment for high altitude conditions (unlike the manual for my Nissan). Assuming your jetting is close or dead on, at high altitude, do you still run the high octane pump gas, or is lower octane help running at such high altitude. The EPA says on their website, "The sale of 85 octane fuel was originally allowed in high-elevation regions—where the barometric pressure is lower —because it was cheaper and because most carbureted engines tolerated it fairly well. At altitude you can run lower octane fuel and actually gain hp. Video answer: Premium vs . 1,586. Thinner high altitude air reduces the compression and combustion pressures in your engine's cylinders. Octane rating is the measure of a fuel's ability to resist "knocking" or "pinging" during combustion, caused by the air/fuel mixture detonating prematurely in the engine. Altitude negates some of the need for higher octane. That doesn't mean it can't be safely used at altitude. As elevation changes at altitude, octane than once you might be tolerated by the future is a problem, especially when automakers are included could run. Reduced oxygen in high altitudes can lead to inefficient, sluggish engine performance because there is less air to feed the internal combustion engine. A quick way of getting your car to play nice is to disconnect the battery for 30 minutes and reconnect. As a result, gasoline marketers sell lower-octane-number (ON) gasoline in the mountain states and other high-altitude areas. clux, Dec 16, 2019 #3. A high octane fuel for raised elevations is ideal & reccommended for steep &high elevations & will make the vehicles performace better. ago. this will reset your fuel trims (unfortunately also your radio, clock, etc). The mean effective pressure in the cylinder is lower due to the lower density air, so you actually can use lower octane fuel. 1 mo. If an engine has a turbocharger, there is little change in pressures at higher elevations, so the same octane should be used at all times in those engines. Past tests of vehicles show that their octane number requirements decrease with altitude. The only benefit of Octane is knock reduction, it is better, it does not have more energy, it is not cleaner! The use of 91 or higher octane "Premium" gasoline is required for this engine. It's a swapped 91 civic with a motor that came from overseas. Although the octane at the economic benefit from hot water boils at higher altitudes require premium gas mileage engines by altitude is a lower octane.

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