My recent purchased 500E was filled up with a different brand of gas other than what It's been receiving. 30 miles after filling up with this new gas (ARCO premium) the CHECK ENGINE light is latched on. Is this problem related to the new fuel or it is coincidental?
The car has very good service record. The O2 sensor was changed 10K miles ago. Since then it went to the dealer for Dyno test twice. I don't know the reason for the Dyno test but my guess is that it is related to the emission system

Thanks
500E
M5

Your first line of defense is to post this question to the TECH section. One of the highly skilled and knowledgable guys over there might have some idea for you to check on. My input to this is-gas brands will not have any effect lke the one you described. Bad gas might cause the problem, but you would notice that the engine is not running right. If he fuel is too low in octane, the knock sensors might cause the light to come on. Another, more simple problem could be the gas cap. make sure the gasket is ok and it is secure. You can try to replace th gas cap, but the best solution is to have the troule code read with a diagnostic tool. Hope this helps...
Gary

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