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Which grade of Gasoline to use ?
I use the 87 grade on my corolla, and the 93 grade
once a month to keep the engine clean(so I was
told), although I am not sure what is actually
cleaned ? Any thoughts on this.
once a month to keep the engine clean(so I was
told), although I am not sure what is actually
cleaned ? Any thoughts on this.
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To clean out carbon deposits, take the car on a
30-40 minute highway drive. The heat the engine generates acts as a very powerful cleaning agent. If you do this daily, all the better.
To clean deposits from the fuel tank, fuel line,
and to eat out any water in the bottom of the tank, periodically use a fuel system cleaner. Make sure and use it on a full tank. It is very caustic and in full concentration could actually damage the fuel filter, and any exposed plastic parts.
I'll put this topic in my placemarks, and ignore the misspelled one that I initially responded to.
thanks,
Andrea.
Nor is it related to the size of the engine or the horsepower what type of fuel you might need. You really need to go by what the manufacturer says and how your cars really runs...pinging should be avoided at all costs, unless it is brief and minor...that clinking noise is your internal engine parts rattling around!
go a lot farther than a tank full of $ 100 gas will
add it when you want that extra couple of horses
also that pinging can be taken care of by timing
True, retarding the timing (you can only do that on older cars safely--the new cars do it for you automatically)will cure the pinging, but also cut way down on your power.
thanks,
Andrea.
Terry
On the topic of oxygenation, power is reduced not because of incomplete combustion, since the (however modest) purpose of oxygenation is to make combustion more complete and improve emission quality, lowering CO. The power loss is due to replacing carbon and hydrogen, the fuel, with oxygen. In contrast, pumping in the oxygen with a turbocharger from an external source readily increases power.
Terry
Technically, we're both right. You are correct that the power loss comes from a lower percentage of hydrogen and carbon. But because of that "unbalance" (more oxygen than the engine would like), the combustion process is not as complete as it could be. A non-turbo engine running oxygas has no idea how to compensate for the extra oxygen, and thus has trouble completely burning it. The extra oxygen, in theory, bonds to the extra carbon monoxide to make carbon dioxide.
Turbos thrive with the extra air pressure because the fuel is also increased to match. This is why turbos are generally made from 4 and 6 cylinder engines - they are attempting to achieve V8 power. Putting oxygas in a turbo multiplies the problem, because again, there's more oxygen than the engine wants, under boost or not.
New Jersey has been fighting the federal EPA for years now, claiming oxygas does not reduce emissions at all, and because of the reduced mpg, forces motorists to buy fuel at a quicker pace, wasting money.
Since I have a diesel, I have to deal with winterized diesel-2. The kerosene keeps the fuel from gelling and waxing - you know when you leave a frying pan on the stove overnight and the grease turns into a thick white gob? Diesel fuel, being an oil, does the same thing during extreme cold temperatures. The kerosene acts as an anti-freeze to delay this gelling, but at the expense of the fuel's overall combustibility. I lose 2-3 mpg on winter diesel compared to straight diesel in the spring and summer.
" A 1990 study by Public Citizen, A Washington DC consumer advocacy organization, found that while 20% of gasoline sold in premium, only 3% of cars actually need it. Premium therefore, cannot improve performance on 97% of all cars, and it doesn't clean engines any better since virtually all gasoline now contains the same detergents in the same concentrations. In 1991, the FTC ordered Sunoco to stop advertising its 93.4 and 94 octane gas as superior in providing engine power and acceleration because the company could not substantiate their claims." THE CONSUMER BIBLE
Another one:
"How widespread is octane fraud? Five separate investigations done since 1990 have found up to an 18% octane mislabeling rate (selling regular as premium). In 1990, the New York City Department of Consumer AFfairs found a 16% rate; by 1993, stepped-up enforcement agains gas cheats had reduced it to 4%"
...(hey, that's still 1 out or 25 gas stations, and that's WITH strict enforcement). Draw your own conclusions next time you fill up...
Exxon was sued a few years back by the feds for pretty much the same thing. The settlement involved Exxon to place electronic and print ads stating that premiunm is only for vehicles that require it, and that regular and plus had the same additives as premium.
Most gasoline ads around here still tout premium grade, but carefully say "for engines that need it or drivers that demand it". That last part of course for thoae who don't care how much money they throw away...
On engines without knock sensor(s), the manufacturer generally sets the timing map conservatively enough to run fine on the lowest octane commonly sold. However, without the close-loop feedback from the knock-sensor(s), the controller can only operate open-loop, that is, advance the ignition timing according to a preprogrammed ignition map. As such, the controller can't "see" the higher octane gasoline and thus won't take advantage of it.
Aftermarket chips generally have more aggressive timing maps, combined with more generous fuel metering, in order to make more power. And usually, they require premium gas.
All bets are off, if you don't take care of your engine. Carbon build-up on piston crowns can raise the compression ratio enough to cause premature engine knock. Likewise, carbon build-up on intake valve can soak up the atomized fuel on cold starts enough to make the engine idle rough.
Knock sensor or not, an engine will be more prone to knock or pinging under high load conditions such as full throttle or towing a heavy load, or high temperature. Higher octane essentially makes the fuel mixture burn slower thus allowing the thin layer of air ahead of the flame front a better chance at insulating the piston crown from melting.
If your truck has know sensor(s), the ignition timing may be retarded so much with regular unleaded under high load conditions to cause you to step on the pedal more and more to get the performance you require. Otherwise, the mpg shouldn't be all that different.
In order to evaluate fuel-cost economics, I once set the time on a 390 CID Ford (during the era of leaded fuel and no EGR valves) as high as pre-ignition would permit on regular fuel and drove for ~5000 miles while keeping a careful record of fuel consumption. Keeping things such as season and driving pattern unchanged as much as possible, I began using premium fuel, reset the time and repeated the evaluation. In this case, the premium fuel cost 13% more but I managed 19% greater mileage per gallon. The reverse would be true for many cars, of course. I don't suggest that others repeat this with today's knock-sensor engines but I cite this because it seems seldom that anyone attempts an objective evaluation of "octane economics."
Also, I agree with the other poster, that unless you're driving under stress and load or with some malfunction, even with a knock sensor you shouldn't notice much change if any in fuel mileage if you switch to premium. But of course, if you've been pinging your little head off, the premium will give relief.
It seems to me that many of us would be pleased to have a reduction of ~15 HP and be able to use regular fuel. But, this is only one isolated opinion.
Shiftright, I agree that tuning for a mileage increase to offset the premium fuel cost would border on miraculous. In the Southeast we also have a $0.20+ price differential. I expected, even in the era of carburetors and ignition points when I made my comparison, that the premium fuel cost would not be justificble.
SEFI is an acronym for sequential electronic fuel injection. It does not describe gasoline type.
Check your owners manual. Don't use a higher octane grade than is specified. There is no harm if you do, but it wastes money.
1)If you can not hear knocking, are you damaging an engine that is recommended to be run on 87 octane?
2) From a stewardship point of view, does a higher octane produce less emissions? If I knew, for example, that using 91 octane would reduce the pollution I was blowing out my exhaust, it would be worth it to me to buy it, even if using it got me no more horsepower.
3)Is there any engine-life benefit from using a higher octane level octane fuel?
And, finally, in lay man's terms, are there any other benefits to using a high octane in a amall sedan, or for the 200 000 mile haul I hope to get from my car, should I just stick with 87 or 88 octane?
I am not familiar with the 85.5 octane. It may be a good modern formulation, but since it's unknown to me, I am reminded of a significant fuel problem of the mid-1980's. As port fuel-injection systems became the norm, many cars experienced heavy fouling on the back side of the intake valves due to fuel chemistry in this different scheme of supplying fuel. Poor driveability, especially with a cold engine, was the result. The whole issue managed to stay pretty quiet but the automakers and gasoline producers put a lot of work into new fuel chemistry and apparently solved the problem. My point, if the 85.5 octane comes from an out of date recipe such as the above, you don't want it in your Saturn.
All indications to me from consumer magazines as well as auto enthusiast publications have been that octane above that specified by the manufacturer is no benefit to the environment or the longevity of the engine. A little extra spent on engine preventive maintenance will benefit the air quality as your car accumulates miles ...with the fringe benefit of reduced fuel consumption and better performance.
The above points are not absolutes but they would bring me back to the 87 octane if it were my Saturn.
I can't even estimate how long it's been since I heard my engine ping. 20 years? 25 years? Maybe more. I guess this is perceived as a major problem for some, but I have always used 87 octane and have never needed any higher in the cars & pickups I've owned.
But you who have posted above have cleared up one puzzle for me. I've never taken anyone seriously who claimed that higher octane provided better mpg figures. But knock sensors and consequent fine tuning of igition timing on the fly provides an explanation, so thanks for providing it.
With the complexities of more than a dozen sensors providing data to the engine control computer, even experienced mechanics may need a long look at your engine to tell you if your model has a knock sensor. The shop manual, of course, has this information.
GM used knock sensors with the Buick turbocharged engines in the early 1980's but, I believe, did not have widespread use until they introduced the distributorless ignition system ...approximately 1986.
Can anyone clarify this further?
My '97 Chrysler Sebring Coupe didn't care, but preferred Sunoco gas to anything else.
My '99 VW Passat (1.8L turbo) requests 91 or better, and I haven't tried 89 to see if it really matters. This car HATES Sunoco. Texaco is fine, as is Exxon.
Anyone know why brands would matter?
My car occasionally (read: never seen my a mechanic) will "shudder" when driving at about 40MPH on a perfectly smooth road.
Could that be knocking.
I don't have any idea what post 49's shudder is, but it doesn't sound like knocking.