what kind of gas do u put in your e class.Ive been using Mexican Pemex gas since I bought my e320. I use the premium 91 octane gas of course Anyone tried it. What are the side effects of using cheap fuel? Maybe that's why my car idles rough.

 

I always use the premium, 91+, Shell V-Power, Super unleaded, etc. Mythbusters did a comparison of the different grades and brands and did find a difference. Although V-Power is $3.79 a gallon here in TN, sometimes I will fill up with that because I feel like I have more power under my foot with a tank full of it. Other times I'm fine with Pilot or BP premium, even costco. As long as it's premium I feel like it's all good.. It's just a car anyhow.

 

Ok kool, I wonder if they can actually test gas to see if its actually 91 octane. i live in Tijuana mexico so its cheaper and more convenient to fill up with Mexican gas. I just hear bad things about it.

 

I use 89 octane (that's midgrade); and it runs fine but I'm an easier driver than my grandma. Mostly steady, part-throttle on flat roads near sea level, and our air temperatures in Virginia are usually less than 100 F (with lots of humidity but the motor doesn't care too much about that). The OBD-II system of engine management in the US includes knock sensors. With any hint of detonation, the computer backs off on the ignition timing, so that helps from burning holes in your pistons in the extreme case but the performance and economy won't be there. Maybe rough idle too.

In the US I believe the signs at the pump because of federal laws concerning anything to do with emissions. Forgot to mention we have 10% alcohol in the fuel, plus stabilizers, detergents, and I don't know what else. I have no experience with Mexican fuel but its probably different. should be easy to find out online or asking around.