I changed my plugs to bosch platinum plugs back in November 00. For the past month I have been getting terrible gas milege. Is it possible that my plugs got "fouled" by bad gas and as a result I am currently paying $2.00 a gallon to travel 15 miles. The current symptoms are:

1) Bad Gas Milage
2) The car feels weak.
3) Bad Gas Milage

Thanks
MaxJoey

 

Bosch plugs have a screw on fitting for sparkplug-wire connection. Out of the box, the fittings aren't on much more than finger tight. If you don't screw them on tighter, you can wind up with a bad connection and poor performance.

 

Some people like the Bosch plats, and some don't. The people who don't like Bosch blame them for a rough idle and uneven acceleration. Even the Bosch detractors don't grumble about gas mileage.

Your car is using too much fuel. These possibilities exist:
- you are burning it
- you are leaking it
- someone is stealing it
- you switched to gasohol


Burning it...
- fuel injectors are sticking open
- "tired" Oxygen Sensors
- bad fuel pressure regulator
- obstructed fuel return line
- clogged air cleaner filter
- bad Engine Coolant Temperature Sensor
- stuck-open thermostat (engine never goes into closed-loop mode)
- transmission defect (never shifts into fourth gear)
- dragging brakes


Leaking it...
Search for fuel leaks by sight and odor. However, some fuel leaks are so
tiny that they escape the human senses. One way to find them is to have
your mechanic use his exhaust gas analyzer. Switch the tester to HC
(hydrocarbons) and then pass the probe along the entire fuel system,
starting at the fuel tank, forward along the fuel lines, past the filter,
all around the engine, then along the return line and back to the tank.
The tester is far more sensitive than the human eye or nose. When the
probe passes near a tiny leak the reading will abruptly increase.


Stealing it...
Perhaps someone is stealing small quantities of fuel, not for its financial
value but as a prank. Install a locking fuel filler cap.


Gasohol...
- You may have switched from one filling station to another,
and not realized that you were also switching from gasoline to gasohol.
- You may live in one of those regions which is required to sell oxygenated
fuel.

Now that MTBE is in disfavor, gasohol is the most common oxygenated fuel.
Alcohol has a lower energy density than gasoline.