2005 Honda Accord 6 cyl Vtech.
Question: in the past 2 months my car is getting 20% less mileage. It happened suddenly--i thought is was the brand of gas, but I am noticing it with all gas types. no change in my driving patterns.

Just turned 100,000 miles. no other noticeable issues except rear wheel bearing noise.

Answer: There are a lot of things that can contribute to bad gas mileage. Of course the basics- has the engine been tuned up and had regular maintenance done, spark plugs with excessive wear / gap can hurt economy, any extra weight in the car, tire pressure set properly, etc. You say you have a noisy wheel bearing. Jack up the car so that wheel is off the ground and see if it has excessive drag compared to the other wheels. A loud hub bearing can drag and effect mileage. Have a computer scan of codes done. Sometimes there will be codes stored even if the check engine light is not on.

There could be a malfunctioning oxygen sensor. this has a lot to do with fuel delivery. It may not set a code, so looking at a live data stream of the sensor may be needed to see how it is acting. A faulty fuel pressure regulator can cause high fuel pressure, thus too much fuel flow through injectors. Normally this would cause other problems as well like blowing black smoke or hesitation though. A sticking fuel injector or several will do the same. Another possibility is that the fuel level gauge is not accurate- giving you a false sense of low economy. As you can see, there are a lot of possible causes, so the basics need to be checked first.

Honda Accord Speedometer Not Working

1994, Honda, Accord. Engine Size : 2.2L.
Question: I can't tell what speed I am going when driving. How can I fix this problem?

Answer: If you mean the speedometer does not work, then you can have a vehicle speed sensor problem, or a faulty dash gauges cluster.