What grad of Gas?
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What grad of Gas?
I have an 02 CLS and with the high gas prices, the cost of 91 octane is killing me. Is it ok to put in the midgrade fuel (89 octane) or regular into my car and will it hurt the performance if i do? I'm really just asking what is the best grade to use in the CLS???
#2
91 octane is probably the best, but I've been told you can run 87 octane without hurting a NA CL. The ECU can adjust to a wide range of gas quality and driving condition.
However, I have never run anything but 91 octane; before and after all my mods. This is because I want the best for my car and with my current mods (including a S/C), it wouldn't be a good idea to run anything less than 91 octane.
Gas prices a starting to dip a little where I live (CA).
However, I have never run anything but 91 octane; before and after all my mods. This is because I want the best for my car and with my current mods (including a S/C), it wouldn't be a good idea to run anything less than 91 octane.
Gas prices a starting to dip a little where I live (CA).
#3
I now drive an accord....
Best is what ever is the highest grade in your area (94 here). If you use less the computer will make the proper adjustments but you will just loose somepower till you put better gas back in it
Edit: you beat me to it
Edit: you beat me to it
#5
Yeehaw
its fine. I've done it a few times. I think there was a small decrease in performance but it could have been mental.
it won't mess up the car or anything.
on the other hand...its only $1.50 difference between 89 and 91 for a full tank of gas.
it won't mess up the car or anything.
on the other hand...its only $1.50 difference between 89 and 91 for a full tank of gas.
#6
There's something else to consider about octane rating; the higher the octane rating, the cooler an engine will run which in turn makes more power.
Here are a couple of interesting links about octane rating:
GASOLINES by the technicians of GROUP K and Octane Rating and VW Engines
Here are a couple of interesting links about octane rating:
GASOLINES by the technicians of GROUP K and Octane Rating and VW Engines
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#8
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Originally Posted by BEETROOT
its fine. I've done it a few times. I think there was a small decrease in performance but it could have been mental.
it won't mess up the car or anything.
on the other hand...its only $1.50 difference between 89 and 91 for a full tank of gas.
it won't mess up the car or anything.
on the other hand...its only $1.50 difference between 89 and 91 for a full tank of gas.
#9
Suzuka Master
Depends...
Originally Posted by zamo
* >= 91
antyhing else will make the engine ping (at least the the Type S)
antyhing else will make the engine ping (at least the the Type S)
Some folks have had trouble even with California 91-octane. There were some TLS folks that had pinging that went away with a few gallons of 100-octane 76 added.
OTOH, if tried 89 octane (they were out of 91 and I was pretty low) -- I had no pinging. As far as performance, it was hot out and I didn't notice any difference.
I've mentioned before that I believe the car can take advantage of 93-octane under cold- weather conditions. (2001 CLS auto + headers + intake).
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i dont knwo where i read it, probly on here, but i rember it said that 87 is the best for our cars and that anything higher was a waste of money. I have a 2.2 is it different for the different models?
#11
Suzuka Master
87 for one, 91 for other
Originally Posted by shanter
i dont knwo where i read it, probly on here, but i rember it said that 87 is the best for our cars and that anything higher was a waste of money. I have a 2.2 is it different for the different models?
I'm pretty sure the 2.2 requires 87 octane.
The 2001-2003 CLS requires 91 octane (it will get buy with less in a pinch).
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Thanks a lot guys. I live in the Kansas City area and the top grade fuel in my neck of the woods is 91. I've only put in 91 so far and i'm going to stick to it.
#13
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...???....
Originally Posted by cls6sp03
There's something else to consider about octane rating; the higher the octane rating, the cooler an engine will run which in turn makes more power.
Here are a couple of interesting links about octane rating:
GASOLINES by the technicians of GROUP K and Octane Rating and VW Engines
Here are a couple of interesting links about octane rating:
GASOLINES by the technicians of GROUP K and Octane Rating and VW Engines
If the engine is pinging or detonating, you heat up, and lose power. However, this is predicated on the octane being low enough to "cause a problem" and reject heat to the cylinder, piston, head, valves, etc. The keyword is MAY.
I've never seen a definitive study that says, "Lower octane means hotter engine."
Obviously, if the car is gets octane that is below a particular threshold for a given condition, it can get hot and lose power. I got no problem with that. However, to simply extend a "possibility" (sometimes) into a "universal fact" (always) is incorrect.
There have been tests done and depending on car, conditions, and other factors, you can actually have a car make less power with higher octane. And. some cars will make more power than the octane specified by the automaker.
It depends...
#14
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Originally Posted by EricL
...There have been tests done and depending on car, conditions, and other factors, you can actually have a car make less power with higher octane. And. some cars will make more power than the octane specified by the automaker...
#15
Suzuka Master
Car and Driver's report...
Originally Posted by Rod
I've heard from a couple people that Ford tells you to only use regular unleaded in their Explorers. Don't know if it's actually true, but would this be one of those cars that performs better with lower octane fuel?
Here is the link to the article *and* in case it goes away, I'll take up too much space with the text in the quoted area.
http://www.caranddriver.com/article....&page_number=1
The results for the E46 M3 are not the same for other cars!!!!
Regular or Premium?
Is premium fuel worth the premium price? Can you hurt a high-octane car by running it on the cheaper stuff?
BY FRANK MARKUS
November 2001
1 2
There's no shortage of opinions on who is to blame for gas-price gouging. One thing that's certain is drivers tend to economize at the pump during extreme price rises—they buy cheaper, lower-octane gas.
In the old preelectronic days, cars would protest such parsimony by pinging like a pachinko parlor, but most modern cars don't complain audibly, so maybe they don't mind. Or do they? And conversely, is there any benefit to be had by springing for the expensive stuff when you're feeling flush?
To find out, we ordered a fleet of test cars—some calibrated to run on regular, others that require premium—and tested them at the track and on a dynamometer.
But before we go into the results, let's go to combustion school. When a spark plug fires, it does not cause an instantaneous explosion of the entire cylinder's charge of fuel and air. The spark actually lights off a small kernel of air-and-fuel mixture near the plug. From there, a flame front expands in every direction, gradually igniting the rest of the air and fuel. This takes some time, as much as 60 degrees of crankshaft rotation.
Meanwhile, the air-and-fuel mixture that the flame front has not yet reached is experiencing huge increases in pressure and temperature. If any part of this air-and-fuel mixture gets heated and squeezed enough, it will explode spontaneously, even before the flame front ignites. This self-ignition is called detonation, or the dreaded "knock."
Now for the chemistry lesson: Oil is a hydrocarbon fuel, meaning the individual molecules contain carbon and hydrogen atoms chained together. Modern gasoline is blended according to various recipes, the active ingredients for which include about 200 different hydrocarbons, each with a spine of between 4 and 12 carbon atoms. One of them, isooctane, consists of 8 carbon and 18 hydrogen atoms (C8H18) and is exceptionally resistant to exploding spontaneously when exposed to the heat and pressure found inside a typical combustion chamber. Another, n-heptane (C7H16) is highly susceptible to such self-ignition.
These two compounds are therefore used to rate the knock resistance of all gasoline blends. A gasoline recipe that resists knock the way a mixture of 87-percent isooctane and 13-percent n-heptane would is rated at 87. Racing fuels with octane ratings over 100 resist self-ignition even better than pure isooctane. The octane ratings for regular-grade fuel range from 85 to 87, midgrades are rated 88 to 90, and 91 and higher is premium.
Mind you, premium fuel does not necessarily pack more energy content than does regular. Rather, it allows more aggressive engine designs and calibrations that can extract more power from each gallon of gasoline.
An engine's tendency to knock is influenced most by its compression ratio, although combustion-chamber design also has a large effect. A higher ratio extracts more power during the expansion stroke, but it also creates higher cylinder pressures and temperatures, which tend to induce knock. In supercharged engines boost pressure behaves the same way. That's why the highest-performance engines require higher-octane fuel.
If you feed such an engine a fuel with insufficient octane, it will knock. Since it is impossible, for now, to change an engine's compression ratio, the only solution is to retard the ignition timing (or reduce boost pressure). Conversely, in some engines designed for regular fuel, you can advance the timing if you burn premium, but whether this will yield additional power varies from engine to engine.
Knock sensors are used in virtually all new GM, Ford, European, and Japanese cars, and most DaimlerChrysler vehicles built today. According to Gottfried Schiller, director of powertrain engineering at Bosch, these block-mounted sensors—one or two of them on most engines and about the size of a quarter—work like tiny seismometers that measure vibration patterns throughout the block to identify knock in any cylinder. Relying on these sensors, the engine controller can keep each cylinder's spark timing advanced right to the hairy edge of knock, providing peak efficiency on any fuel and preventing the damage that knock can do to an engine. But, noted Schiller, only a few vehicles calibrated for regular fuel can advance timing beyond their nominal ideal setting when burning premium.
Older or less sophisticated cars with mechanical distributors do not have the same latitude for timing adjustment as distributorless systems do and therefore may not always be able to correct for insufficient octane or additional octane.
We should note that even cars designed to run on regular fuel might require higher octane as they age. Carbon buildup inside the cylinder can create hot spots that can initiate knock. So can malfunctioning exhaust-gas-recirculation systems that raise cylinder temperatures. Hot temperatures and exceptionally low humidity can increase an engine's octane requirements as well. High altitude reduces the demand for octane.
Got all that? Good. Let's meet the test cars and ponder the results. At the lower-tech end of the scale was a regular-gas-burning 5.9-liter Dodge Ram V-8. This all-iron pushrod engine has a mechanical distributor and no knock sensors, so the computer has no idea what grade of fuel it's burning. A Honda Accord V-6 with VTEC variable valve timing represented the mainstream-family-sedan class, and a 4.6-liter V-8 Mustang stood in as an up-to-date big-torquer. Both of those were designed to run on regular unleaded. Our premium-grade cars included the hard-charging 333-hp, 3.2-liter BMW M3 straight-six boasting individual throttle by wire for each cylinder and enough computing power to run Apollos 11 through 13. A Saab 9-5 gave us a highly pressurized 2.3-liter turbo. For the sake of repeatable track testing, all but the M3 were equipped with automatic transmissions.
We ran all vehicles on both grades of fuel, at a drag strip near our offices and on a Mustang eddy-current dynamometer that was offered to us by the engine-tuning pros at Automotive Performance Engineering in nearby Clinton Township, Michigan. On arrival, all fuel tanks were drained and filled with 87-octane Mobil regular fuel and driven for two days before track and dyno testing. The tanks were drained again and filled with 91-octane Mobil premium and again driven for two days to allow time for the engine controllers to acclimate to the fuel type and tested again. All dyno and track results were weather-corrected.
Our low-tech Ram managed to eke out a few extra dyno ponies on premium fuel, but at the track its performance was virtually identical. The Mustang's knock sensors and EEC-V computer found 2 hp more on the dyno and shaved a more impressive 0.3 second off its quarter-mile time at the track. The Accord took a tiny step backward in power (minus 2.6 percent) and performance (minus 1.5 percent) on premium fuel, a phenomenon for which none of the experts we consulted could offer an explanation except to posit that the results may fall within normal test-to-test variability. This, of course, may also be the case for the gains of similar magnitude realized by the Ram and Mustang.
The results were more dramatic with the test cars that require premium fuel. The turbocharged Saab's sophisticated Trionic engine-control system dialed the power back 9.8 percent on regular gas, and performance dropped 10.1 percent at the track. Burning regular in our BMW M3 diminished track performance by 6.6 percent, but neither the BMW nor the Saab suffered any drivability problems while burning regular unleaded fuel. Unfortunately, the M3's sophisticated electronics made it impossible to test the car on the dyno (see caption at top).
Our tests confirm that for most cars there is no compelling reason to buy more expensive fuel than the factory recommends, as any performance gain realized will surely be far less than the percentage hike in price. Cheapskates burning regular in cars designed to run on premium fuel can expect to trim performance by about the same percent they save at the pump. If the car is sufficiently new and sophisticated, it may not suffer any ill effects, but all such skinflints should be ready to switch back to premium at the first sign of knock or other drivability woes. And finally, if a car calibrated for regular fuel begins to knock on anything less than premium or midgrade, owners should invest in a tuneup, emissions-control-system repair, or detergent additives to solve, rather than bandage, the root problem. Class dismissed.
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