Coming home with a Buickload

[Captainclock]

Originally Posted by MadMan

As a rule of thumb, cars are designed to get roughly 200 miles per tank. However, if you are absolutely certain you were getting more mpgs before the catalytic problem, the reverse of what you said is likely true. That the converter is suffering because of the mileage problem. Ask a real mechanic to do a good tune up and see that the motor runs right first.

OK, that's interesting because everywhere I read online said that a failed rear Oxygen sensor (which is part of the catalytic converter assembly) would cause a car's fuel economy to drop off.

Also why would it be a "general rule of thumb" that cars only get 200 miles on a tank of gas (which for me is only about a week) when my old car which had a 4 cylinder engine in it could easily get 300+ miles on a tank of gas which was about 3 weeks on a tank of gas and my Oldsmobile I had before that which also had a 3800 like my Buick I have now got pretty close 300 miles on a tank of gas which was roughly 2 weeks on a tank of gas?

Also I don't understand what you mean by

However, if you are absolutely certain you were getting more mpgs before the catalytic problem, the reverse of what you said is likely true. That the converter is suffering because of the mileage problem. Ask a real mechanic to do a good tune up and see that the motor runs right first.

because like I was saying above I had read in several online forums pertaining to car maintenance that said that the rear oxygen sensor (which is part of the catalytic converter assembly) is what causes poor fuel economy because the sensor isn't able to send the ECU the right fuel/air mixture information so then the engine actually ends up burning more fuel than it needs to, because its not getting the proper amount of air mixing into to fuel.
And actually I have had a mechanic look at the car already and he said that I needed the whole catalytic converter replaced because that's the code my car's OBD II is throwing for the Service Engine Soon Light which he also said that's the same code for the rear oxygen sensor but because the rear oxygen sensor usually gets seized onto the catalytic converter making it impossible to remove he just replaces the whole catalytic converter assembly and is done with it. As far as any other engine problems go supposedly the valve cover gasket is shot but I'm not sure if that's actually the case or not because the engine does leak a little oil every once in a while which then gets onto the exhaust manifold which then causes a burned oil smell every once in a while because the oil is being burned off the exhaust manifold, but I'm also wondering if it isn't just because the engine was filled too full of oil and because of that some of the excess oil is being sprayed out of the engine onto the exhaust manifold which is similar to what a lawnmower does when its overfilled with oil, I say this because the dealership I got this car from had changed the oil on my car before I had bought it and they had filled the engine too full by a quart, inspite of the "oil leak" the oil level has stayed pretty consistent since I've had it.