Hey all,

My check engine light came on a few weeks ago - it was conveniently the day before I was bringing it into the dealership for an oil change too. I'm still under warranty so they ran diagnostics and it was all of the O2 sensors. They checked the sensors themselves and they were all fine. They were a bit perplexed but ordered the new sensors.

I went in today for the new sensors to be installed and when they were done the work the tech guy came out and told me that they had gotten some new information since I had my car in initially. Turns out that someone figured out that Sunoco and Shell's within about 100 miles of Boston have been diluting their gas with extra ethanol - up to 25% on some tests! He said that European cars have more sensitive O2 sensors than their American counterparts so it shows up in the O2 sensors. He said they called over to a Mercedes place in Europe and asked if they had been seeing the same thing and the answer was "everyday!"

With gas prices on the rise - I expect this practice may not be just an isolated thing. Hope this post helps some people!

 

Makes sense. The equivalent lambda values for ethanol are totally different than for gas.

This advice might save headaches for a lot of people.

 

What's a lambda value?

 

Nernst cell O2 sensors use a lambda value calibrated to the fuel. The lambda value is the ratio of unburned oxygen in the exhaust to the rate of flow over the sensor . In a gasoline engine, therefore, extra oxygen means a lean condition (high lambda) and less oxygen means a rich condition (low lambda).

 

Thank you sonoronos

 

I usually fill-up at either a Cumberland Farms Gulf or the Sunoco station next door. Both premium fuels are suppose to be 93 octane. My hometown is well within a 100 miles of Boston. As a matter of fact, I live approximately 32 miles south of Boston. I've put roughly 2300 miles on my XFire since I bought it and have not experienced anything like you mentioned.

I drive past a tank farm off of Allens Ave in Providence when I go to my boat. I see the Sunoco, Gulf, Shell, and other gas tankers in there filling their tanks for distribution to New England area gas stations. They are all getting their product from the same source.

Now I don't know how far they travel out of the Port of Providence to deliver gas, but I would imagine they may go beyond 100 miles from there. I would imagine what you have experinced may be an isolated incident and not a common practice.

Bob

 

Heck even I live within 100 miles of Boston.
Actually Bob if you look at a couple of other threads here on the forum this is a problem for a lot of Mercedes,Lexus and other high end cars. It is also posted on the two mercedes forums I read. It was even talked about on WBZ tv news.

 

Phil, ...I stopped watching WBZ-TV when they started axing their more senior people like Scott Wahle, Bob Lobel, and Joyce Kulhawic. I'm surprised they didn't axe Jack Williams but his "Wednesday's Child" segments are good PR, so they just had him whiten his teeth to stay around a bit longer. I grew up watching the "old reliables". The new people seem like pretty puppets to me.

I still think this situation is not more than just a few isolated incidents. The car dealers probably built it up a little so they can get more cars in for service either on or off warranty. How many of these high-end cars have you seen broken down on the side of the road?

Bob

 

On a recent trip from our home in Aldergrove BC to Seattle, the check engine light came on, topped off the tank in the US, still on, drove to Seattle and on the way home the next day the light went off and has not come one since, as Canadian and US mixes are different I expect this to occure from time to time, as we spend most of our travel time in Washington and Oregon. Will monitor what gas we buy if and when the light comes on. I have noticed one thing with US gas on all our vehicles, they seem (seat of the pants dyno) to run a little better. Canadian gas is treated for weather, so winter gas could still be in a lot of gas station tanks even as late as early summer.

The one oddity in this is a lot of the gas in BC comes from the Cherry Point refinery in WA.

where is spell check when I need it?

 

This same thing happened with me! i USED SUNOCO gas.. it took about four tanks of other gas to get rid of the check engine light. They were going to replace the computer system since all the o2 senors were having a problem at the same time.. they figured it was a bad computer... once the light turned off i didnt buy gas from that location in boston.. i get it at a Hess close to my house and the light hasnt been on again..

thanks for the info.. mine was never diagnosed.. it just went away after a while.. while waiting on a new computer...

 

Has anyone here with a CEL gotten the codes run to see what they indicate the problem is ??