Check Engine Tip for MB owners

[mittalv]

I moved to California recently and wanted to share what might be useful to some MB owners in the Golden State. In the North East, I used to fill my 2000 MB S430 with 93 octane gas. All NorthEast pumps use MTBE in their gas. When I got to California, I discovered that most pumps only have 91 octane at best and that my Check Engine light comes on. After the gas level would drop to 3/4, it would go off. The local pumps also use MTBE. Here's the interesting news however. I have tried this many times and it is absolutely not a coincidence that when I fillup at a "76" gas station, the Check Engine does not come on. They use Ethanol rather than MTBE. I do not work or have any relationship with this company. In fact, I had never heard of them till I got here. So to all MB owners out there, try and find a brand of gas that does not use MTBE...

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[phungpho]

First, can you explain what MTBE means ?
Secondly, what's the difference between Ethanol and MTBE.
Is the Mercedes engine is designed for Ethanol ? I thought Ethanol is a different kind of gasoline that is used in Indy Cart racing and not for regular engines !

Thanks

[mittalv]

I am no chemist and so all I can tell you is that Ethanol and MTBE is used to "oxygenate" gasoline in order to meet a federal mandate to sell gasoline that results in fewer emmissions.

Almost all gas stations sell gas with MTBE. "76" seems to be the only exception I know off. I am also not very happy that I cannot easily get 93 octane here in California, especially given that we pay so much for gas anyway.

By the way, does the check engine light in your MB also sporadically switch on?

Regards,
Vikram

[phungpho]

Vikram,

So far, I haven't got that problem: Check engine light turns on. However, the ABS + ESP system didn't work. It took them 3 days to get the part and fix the car.
Oh, by the way, for gasoline, I use Mobil or Shell.

Thanks

[genome]

93 octane, is your car programmed for that? all mercedes are designed to run best on 91 octane.

don't want to get all environmental californian on you but mtbe is a horrible thing. completely destroys our drinking water. i really never cared about "these environemtal issues" before, until i lived in a country where it was too late for environmental measures. DON'T USE MTBE OXYGENAED GAS.

[mittalv]

I am sure that the MBz like most modern engines adjusts the timing and other paramaters as different octane is used. 93 octane is commonly available on the East coast and I would use it if I lived there. I recoginze that given all the power available from the V8, the difference would not be very noticeable.

I agree that MTBE is terrible on the environment and the car. Right now, I only know off "76" gas stations selling gas which is MTBE free.

If anyone knows of other brands, please let us in on the secret as I am unable to find "76" gas stations everytime I am travelling someplace new.

[Nektopoli]

Originally posted by genome
93 octane, is your car programmed for that? all mercedes are designed to run best on 91 octane.

don't want to get all environmental californian on you but mtbe is a horrible thing. completely destroys our drinking water. i really never cared about "these environemtal issues" before, until i lived in a country where it was too late for environmental measures. DON'T USE MTBE OXYGENAED GAS.

Ok and how do we do that, Oxygenaed gas is all we can get here in the Mid-Atlantic from Nov to Apr, I watch my gas milage drop 3 to 4 MPG. Oxygenaed gas does reduce immissions but only on car with out O2 sensors.

NP

[genome]

oxygenated gas does not have to be MTBE oxygenated gas.

[Air Marshall Eldritch]

I thought ALL cars these days had O2 sensors(?)

And didn't the EPA finally admit that MTBE was polluting the groundwater a couple years back?

[mittalv]

If you guys note my and Genome's posts, we have no choice but to buy oxygented gas in the US.

However, the trick is to find gas that is oxygenated using Ethanol rather than MTBE.

[genome]

thank you mittalv. gas is oxygenated, but you dont have to use the MTBE oxygenated gas.

that MTBE stuff is an ecological nightmare. yes the epa did admit a few years back that MTBE is a poison and we were using to "clean" up the air. this MTBE stuff destroys our groundwater supply.

DON"T USE MTBE OXYGENATED GAS.

-stepping off soapbox-

[lars]

MTBE = methyl tertiary-butyl ether, which is obviously quite different from ethanol. The 1990 Clean Air Act Amendment in the United States required fuel oxygenates to be added to gasoline in some metropolitan areas to reduce atmospheric concentrations of carbon monoxide, carbon dioxide, and ozone. MTBE is the most commonly used fuel oxygenate because of its low cost, ease of production and transfer, and blending characteristics.

MTBE has become an important groundwater contaminant because of its mobility, persistence, and potential toxicity. It enters groundwater primarily from the underground storage tanks at gas stations, which leak more commonly than you might think. The use of MTBE has become controversial, due primarily to issues with contaminated groundwater supplies.

California has banned the use of MTBE, effective 31 December 2002. I do not know what will replace it, so please post if you do.

[darkLCD]

From my understanding, there are potentially 4 other replacements that could serve to oxygenate gas:

(1) Ethanol which is ideal because it does not pollute the groundwater. However, ethanol is expensive, so we will have to see if this is the preferred substitute for MTBE.

(2) ETBE (ethyl tertiary butyl ether)

(3) TAME (tertiary amyl methyl ether)

(4) TBA (tertiary butyl alcohol)


(2), (3), and (4), will pollute the groundwater just like MTBE. They are cheap, so I have a bad feeling that gas refineries might go for these instead of ethanol. Phasing out MTBE could bring out the evils of ETBE, TAME, and TBA.

It is quite interesting and correct that Unocal 76 uses ethanol to oxygenate their gas (they seem to be the only one). I'm filling up on ethanol gas at Unocal now because there has been reports of MTBE gas damaging fuel systems...maybe ethanol gas won't do the same, and the idea of not polluting our groundwater is an added benefit (trust me, I'm no environmentalist, so this is not my main reason for switching over).

[lars]

It's going to be difficult to find winners in the replacement for MTBE. Ethanol has at least two drawbacks.

1) Ethanol has less available energy per unit volume than unformulated gasoline, and so reduces fuel economy in a small way. I don't use ethanol-formulated gasoline, but a friend says he can see a decrease of one or two MPG when he does.

2) Ethanol is not quite as green as many people make out. The source touted as having the most environmental benefits is biomass, typically the non-consumable part of cereal or corn crops. If a farmer can sell this part of the crop he or she probably will. In the alternative, this part of the crop is ususally plowed back into the ground where it helps maintain soil structure and fertility.

In cars with oxygen sensors, the emissions circuitry responds to oxygenates in the fuel by enriching the mixture, lowering fuel economy in the process. How much it does so is a function of programming by the manufacturer, and it would be interesting to know some generalities about how MB has calibrated the fuel and emissions systems to cope with MTBE.

[darkLCD]

Odd, I'm actually getting better mpg by about 2mpg in my commuter car, Lexus IS300. The sticker on this car was 18mpg (local)/20mpg (freeway) and they weren't joking about the 18mpg. This car guzzles gas so when there is an increase in mpg, it's extremely perceptible.

Ethanol doesn't contaminate the groundwater. That's green enough for me. The drinking water is bad enough in CA, there's no need to make it worse with MTBE or it's relatives.

[Air Marshall Eldritch]

I notice a decrease in mileage from around 500 miles to less than 450 on a full tank (I do mostly hwy cruising) when oxygenated gas is forced on us come October.

Given that, the whole idea is flawed. I pollute less per gallon (or so the EPS claims), but I have to burn more over the same distance. Is this the New Math?