low octane fuel/ethanol in the escort

my manual says that i should avoid fuel octane-rated lower than 87.

i just drove across the country, including a tank of 86 and a tank of 85.5. although there are obviously other variables, i coudlnt help but notice that the best mpg i got all trip were with these two tanks.

could they possibly be related?

could it have anything to do with ethanol additives?

anthony

I've run 85 and 86 octane in my car and it ran fine. I think it was New Mexico and Utah. I used to work with fuel and here is something to consider: Fuel will expand and contract with temperature changes. Let's say you have 10 gallons of gas. It gets really hot and that gas expands to 11 gallons (hypothetical). This gas is still going to have the same amount of hydrocarbons and therefore only going to take you as far as 10 gallons would have. So it will look like your mileage is worse. On the contrary, Let's say you bought 10 COLD gallons of gas. This is going to have MORE hydrocarbon molecules than normal and thus you'd be getting better mileage because your COLD gas at a normal temperature might actually be 11 gallons. It all boils down to how many hydrocarbon molecules there are per gallon. The colder the fuel the more molecules, the hotter the fuel, the less molecules. Hope this makes sense :screwy:

Case in point, I just read an article about 'Flying J' truck stops. They will park a fuel tanker in the sun for a few days. Let's say they brought in a 7,500 gallon load of diesel. After sitting in the hot sun a few days it might expand to 7,800 gallons. So they get 300 gallons for free when they dump it in their tanks. What prompted this article was a driver who said his mileage went down when he put warm diesel in his tanks. (He was actually putting a thermometer in it.)

Anyway, my guess is that you bought your low-octane gas somewhere where it was cool and compared that mileage to the mileage somewhere where it was hot. Differnt temperture equals different mileage. Just a theory. :eek7:

This is probably more info than anyone needs but consider this: When a company is buying, storing and selling millions of gallons of fuel they can't afford to be affected by the temperature change. The amount of fuel in a storage tank is constantly changing due to temperature and barometric pressure. So the industry standard is to buy and sell fuel at what the quantity would be if the fuel was at 60 degrees fehrenheit. They do this by a formula called 'Temperature Conversion'. It's a formula that considers temperature and specific gravity (caused by barometric presure). So if you had an 8,000 gallon load of warm gasoline come in you might only pay for 7,900 gallons. Because that's how much you'd have if it were at 60 degrees. On the other hand, in the winter, if that same 8,000 gallons came in you might pay for 8,300 gallons because that's what it would be at 60 degrees. The problem with the consumer is that this temperature compensation process doesn't take place at the pump. So you get more bang for your buck in the winter than the summer. That's my story and I'm stickin' to it. :grinyes:

As if I didn't already say enough, l want to mention octane. An octane rating is a fuels ability to resist 'predetonation' or 'pinginging' as it is also called. The octane level has nothing to do with power. This is one of the dirty little secrets of the petroleum industry. If your car doesn't ping on 87 octane then you are throwing your money away buying anything else.

Alcohol fuels, like methanol, get worse fuel mileage than gasoline. Therfore when there is methonol in the fuel you will typically get worse mileage. :2cents:

Alcohol fuels, like methanol, get worse fuel mileage than gasoline. Therfore when there is methonol in the fuel you will typically get worse mileage. :2cents:


your saying ethanol additives right? well i have ethanol additives im my fuel as well and i find my car runs real good on low octang with ethanol additives but runs best on mid grade with ethanol additives

ethanol additives are made from corn oil WTF That is nutz

peace out



www.nlc.741.com (http://www.nlc.741.com)

I only use 91 octane in my '93 1.9. Not for power, smoothness, or quietness. I'm tired of changing valves in the head.

Most people buy the most expensive new car they can possibly afford, and find the payments rather too much, so they run cheap gas, skip maintenance, and so on. Twelve years later, and it's time for all that neglect to catch up with the present owner. One can't make up for a hundred thousand miles on cheap gas, but might avoid further damage.

Your foot maybe got lighter as you drove on the cheap stuff. Hope you like changing valves 50 miles outside of Omaha.

What does fuel octane have to do with you changing valves? High Octane fuel is'nt "cleaner" or resist damage to internal parts. If your constantly changing valves then there's somthing elese wrong, it has nothing to do with the octane your using.

AzTumbleweed hit the nail on the head: "An octane rating is a fuels ability to resist 'predetonation' or 'pinginging' as it is also called. The octane level has nothing to do with power. This is one of the dirty little secrets of the petroleum industry. If your car doesn't ping on 87 octane then you are throwing your money away buying anything else."


sixleggedinsect, you got better milage because you "drove across the country". Long trip's with few stop's, few cold starts and a constant speed give a lot better milage. The fuel octane and temperature is a very small varible compared to the driving style.

sixleggedinsect, you got better milage because you "drove across the country". Long trip's with few stop's, few cold starts and a constant speed give a lot better milage. The fuel octane and temperature is a very small varible compared to the driving style.

well, maybe, maybe not. ive been monitoring my mpg pretty closely with this new car (new used car) and id been driving a couple thousand miles before that low octane tank. lots of highway miles and warm starts and constant speed, etc.

but- as a poster mentioned, theres no use extrapolating mpg from one tank. too many variables. i just posted because i had heard that low oct gas would decrease mpg, when my two sample tanks did the opposite, and wanted to check in with the experts.

incidentally, im in wyoming now, where 85 octane is default regular. ive had a couple tanks of that now, and we'll see how it goes.

no changes in engine noise, but then i dont really know what pinging sounds like. i assume that means my engine is not pinging..

cheers,
anthony

Pinging is usually most evident when you go uphill and have to depress the throttle way down, you'll know it if you hear it.

Computer controlled motors have an octane sensing, or ping detector. The spark will be retarded to compensate for it, providing less power.

Which year and motor do you have, there have been a few?

Pinging is usually most evident when you go uphill and have to depress the throttle way down, you'll know it if you hear it.

Computer controlled motors have an octane sensing, or ping detector. The spark will be retarded to compensate for it, providing less power.

Which year and motor do you have, there have been a few?

currently a 97 spi 2.0.

before i had a 93 1.9, which also did not ping on low octane gas.

(once again, assuming i will notice pinging without anyone having pointed it out..)

Good mill. But I still suggest you run the better gasolines, higher octanes, good additives. You may still be a hundred thousand miles from an obligatory valve replacement, then again it may be a lot closer than we suspect.

Argggh! I hate to burst you guys bubbles, but I'm a chemist and after reading this entire thread, I am getting dizzy with all the wrong statements, wives-tale beliefs and half-truths various folks have put on this board. Pardon my rant, but I couldn't just sit by quietly and lurk my way through this thread. I won't point out specific names to avoid embarrassing any individuals, I hope everyone thinks that's fair because I simply want to set the record straight.

1. NOBODY got it completely right about octane. Some got it part right. It's true you shouldn't waste your money on higher octane than your car needs to avoid knocking. It's also true that higher octane than your engine needs won't help your engine or give you more power. Things that determine octane requirement are the compression ratio of the engine, the combustion chamber shape, the altitude, engine temperature, whether or not there are foreign carbon deposits, the spark advance and the type of spark plug being used. BTW, some folks didn't know what knocking sounds like. To me, it sounds like shaking pebbles in a coffee can, kind of a dull, rattling or clattering sound. Very similar to the sound of a diesel engine. In many modern cars with computerized anti-knock systems, you simply won't hear it, spark is retarded to prevent it. But performance will be slightly reduced without you knowing about it. That's why you should follow the automaker's octane recommendations. There's nothing in it for them to inflate that number, so it's a good idea to accept it.

The thing everybody missed about 85.5 and 86 octane working OK in your Escort when you were travelling out West is that octane requirements by most auto manufacturers are set at (approximately) sea level. Most of the world lives within a thousand feet of sea level, so octane requirements there are what most people talk about. Here's the kicker: Octane requirements go DOWN as altitude increases. An engine that needs 87 octane at sea level may only need 85 or even less in New Mexico, Utah, Colorado, and other places where the altitude can easily be thousands of feet higher than sea level. Adding ethanol to gasoline reduces the octane rating, but in Western states at higher altitudes, they can get away with it.

The reason being, with higher altitude, there's less air pressure. With each intake stroke of an internal combustion engine, there are fewer molecules of oxygen, nitrogen and a few other gases minutely present in the atmosphere getting into the combustion chamber to mix with fuel. When that smaller amount of air is compressed according to the compression ratio of your engine, the pressure inside the engine will be lower as the spark plug ignites the mix. The lower that pressure, the lower the chance of pre-ignition (knocking). With reduced propensity for knocking, you can get by with lower octane fuel. By the same token, because of less air (ie. less oxygen, since that's the part of the air your engine needs), to run best, the engine needs less fuel, which means leaner. BUT, that doesn't mean you'll get better mileage at high altitude. Less fuel being burned with less oxygen means less power output. So the engine needs to run at wider throttle to generate the same power as at sea level. It's the old rule, you don't get sumthin' fer nuthin'. Years ago, when cars were carbureted, engines in the mountain states were rejetted leaner for better high altitude performance. Many modern fuel injected engines can automatically compensate (within limits) by cutting back on the amount of fuel injected each stroke at higher altitudes. Hopefully I've stated this clearly enough so everyone will understand the connection between altitude and octane requirement.

2. Another point: all states have Departments of Weights and Measures. One of their regular duties is to carefully measure fuel delivery quantities of the pumps used at gas stations. I've witnessed this being done at a gas station and the state employee told me they can measure accuracy within a tenth of one percent. They use accurate thermometers and special huge inverted cone-shaped tanks mounted on trailers in their checking process. Gas station pumps are designed to deliver accurate quantities of fuel at any delivery pressure or temperature normally encountered. Contrary to what has been said in this thread, gas pumps DO compensate for density variance due to temperature changes. The bottom line is you get the same amount of energy for your money from gas bought in July in Phoenix as you do in Anchorage in January. You can think of it like you are buying gas by weight, because that's what's actually happening.

3. In addition to pumps being accurate at various temperatures, the temperature where gas is stored in underground tanks at gas stations is relatively constant. Once you get a few feet below grade, it doesn't vary much all year round. Tanks are typically buried from 10 to 15 feet below ground. Even if the gas sits in a tanker truck for several days in the hot sun, once it's put into an underground tank, it quickly cools back down. The earth is a much better conductor of heat than air. So even if the story about "Flying J" trying to help their business by parking tankers in the sun to warm up for three days were true, within a few hours after that warm fuel was put into underground tanks, it would be cool once again. It's hard to believe with the cost of a tanker and driver than any business would let it sit around idle for days waiting to warm up! All these reasons add up to why you should NOT believe on a hot day you're getting less gas for your money, or conversely on a cold day you are getting more. It's simply not true.

4. Atmospheric pressure changes have about as much to do with getting a full gallon of gas as your sign of the Zodiac! Atmospheric pressure has absolutely nothing to do with the specific gravity of the fuel. Liquids for all intents and purposes, are NON-compressible. That's why hydraulic jacks work so slick.

5. Adding ethanol to gasoline makes about as much sense as watering down fine whiskey. One posting made the point that alcohol reduces fuel mileage when added to gasoline. TRUE. Gasoline is a better auto fuel than ethanol. That's because there are more calories (energy) in a gallon of gas than a gallon of ethanol. If it was really better, they'd sell 100% ethanol for our cars, American farmers would be tickled pink and the Arabs would be crying in their oil. Problem is, cars would run like crap if they ran at all. And your tank would have to be much bigger because your mileage would drop significantly.

The farmers lobby has a lot to do with why you see ethanol added to a lot of the fuel in the heart of the USA. It gives them a better market for their corn or other grains which can be fermented to ethanol. Like lots of other things in life, money talks.

6. My last point agrees with what a couple postings touched on. If you want to compare mileage from one tankful to the next, you should make sure you're driving at the same altitude, temperature, humidity, speed, road conditions, trip distances,and driving habits. And you need to make sure you fill your tank to exactly the same level from one tankful to the next. That means topping up s-l-o-w-l-y rather than just letting the auto-shutoff click off. Only then can you decide if one kind of gas delivers better mileage or performance than another. I really hope this posting clears up a lot of misconceptions about this whole subject.

Very interesting. You certainly cleared up a lot of things for me. Now, if someone could explain why gas is $2.95 a gallon.

Hey Dave, lucky guy! Where are you that gas is only $2.95 a gallon? I just paid $3.29 in western NY. But at least it's down from high of $3.59 a week and a half ago.