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Gas mileage dropped for my 2006 Honda pilot 2wd

I have a 2006 Honda Pilot 2wd with 54000 miles. Its gas mileage dropped from 21 to 17 recently with the same driving habit and same route(from home to work and some city and some highway). I changed air filter, checked air pressure, changed transmission oil and even used gas system cleaner. no help at all. Do you have any other suggestions? Thanks

The EPA estimates put this vehicle at 18 MPG for the combined average. 17 MPG is pretty close to that. Over how many tanks of fuel as it been getting 17 MPG? If it’s just one or two tanks, then it could just be an anomaly. But at any rate 17 MPG is within the ballpark for fuel mileage for this vehicle.

Do you always buy your gasoline at the same place? A 10% ethanol mix can lower your fuel economy.

If the vehicle is not reaching operating temperature, it won’t get as good mileage than if it does get fully warmed up. In summer weather, it is difficult to notice that the engine is running too cool because you aren’t using the heater. Check the temperature gauge. If it is not reading in the normal operating range, you may need to replace the thermostat.

Does the drop in MPG correspond to increased use of the AC?

Since I purchased this Pilot(brand new), its MPG has been 20-21 or more. It dropped to 17 just recently. I changed engine oil at HTB recently, before I changed it in Firestone. I guess the engineer oil is the possible problem. Another guess is the brake pads which was changed not a long ago. Thanks you for your helps.

I have been using 87 with 10% ethanol mix and it should not be a problem except the gas quality changed recenlty. Thanks.

I did not know this, but I will check to see whether temperature is in the normal range. But what is the normal operating range? in the middle of the meter?

I am in Texas and has to use AC all the time, I do not think lower MPG is related to AC usage.

Thank you all for the help and suggestions. This pilot has been running at 20-21 MPG for over four years. The one tank of gas (16 gallons)could run 330-340 miles. Right now it runs 290-300 miles with about 17 gallons. I use this Pilot for work and drive on the same road and no driving habit changes. I think something is not right, but I do not know why. I have tried everything except change Spark Plug, and use dealer recommended engine oil 50W-20. I really do not know what enginer oil NTB used. It might be coincidence that the MPG decreased after I started change engine oil in NTB. I will try other auto shop. Thank all again.

Even though the car companies say (iridium) spark plugs can last 100k miles I don’t trust that they always can.
So I think it’s a good time for new plugs.
4-5 years is a good time to change coolant, thermostat and maybe radiator hoses too,
especially down in Texas.

Cruise a few miles on the highway and avoid braking, then stop using minimal brakes.
Feel the wheels for temperature. A wheel hotter than the other side may have dragging brakes.

I will try to change the Spark Plugs, coolant by my own this weekend and test my brakes as well. I will update the MPGs thereafter. By the way, what is the thermostat? Can I change it by myself? Thanks again

I went 100,000 miles on my original Odyssey spark plugs without a change in performance.

I’d try fresh 5W-20 Oil first. Maybe try a different gas station too.

Probably not a thermostat problem, that would show up in cold weather, not hot.

I might ask, How do you measure mileage and how often do you do it?

BTW a bad thermostat could reduce efficiency, even when it is warm outside.

I’ll add that from your other messages, I suspect you are properly measuring mileage and I would consider the thermostat as a long shot.

I fill the gas tank to full and set the trip meter to 0. After I fill gas next time, I record the mileage and gas I filled and set the meter to zero again. The MPG = mileage(miles)/gas(Gallon). I montitor the MPG all the time and found the big drop recently.

I notice earlier in the thread you mentioned that you are going a shorter distance per tankful, this is the incorrect way to measure mpg. I then notice that you corrected yourself and used the miles traveled divided by fuel used, this is the correct way to measure mpg.

When we recieve a post about an unexplained loss in mpg it is often revealed that the OP (you) are using the first method I described (the wrong one) to deterimine mpg.

It doesn’t matter how fuel consumption is measured if the method is repeatable and the absolute value isn’t needed to notice a change.
If the OP got the same mileage over and over for the gauge to reach a certain point, then suddenly one tankfull is significantly different then something has changed, if only the gauge.
Some people (like my brother) measure MPG at each fillup and record the numbers and some (like me) just note mileage to the halfway mark or whatever.
If a car is new to me or I suspect a problem or I’ve made some change, then I’ll figure the actual MPG.

You can’t depend on the meter indicating the same anount of gas in the tank through out the cars lifespan. I am talking about a situation where someone says “I usually have half a tank left after my work week driving and now it is a needle width below the half way mark, I must be using more gas”, this type of conclusion could be in error.

Myself I have never checked my mileage in 40 years of driving, it is what it is. Some say they check mileage so they can tell if something is wrong with the car, not a good, or should I say, there are much better ways to tell if the car is running poorly.

The MPG should be a good indicator for overall performance especially it runs on the same route and same driving time and style. This is reason I monitor the MPG all the time. If the MPG drops too much (about 20% in my case, from 21 to 17), I think something must be wrong. It looks like tire pressure, air filter, gas system cleaner do not do too much. It is kind of waste of money. At least they should not be as important as the dealer or auto shop have been telling us. Just a thought.

I called NTB where I had my engine oil changed last time. They used 5w-30 for my Pilot and I found the manual suggestion is 5w-20. I think it might be part of the reason for the lower MPG. Anybody has the similar experience? NTB should know the right oil for the car, but they just did not do in the right way.