Gas mileage tips?

[Crs]

Hello everyone, i have a 2006 Mdx with 77,000 miles and noticed that my gas mileage has dropped about 3 mpg in the last 2 years or so. Right now i'm averaging 15 mpg mixed driving and fill up with either Shell or Chevron 91. All maintenance is up to date, with no driving habit changes. Any tips are appreciated! Thanks!

[nsxtasy]

First, make sure you're calculating your mileage accurately:

1. Don't calculate miles (or km) per tank. Calculate miles per gallon.

2. Average your mileage over several tankfuls (dividing total mi by total gallons), to minimize any differences from one tank to another resulting from how full they are (when the pump clicked off).

3. Do your calculation using gallons from the pump and miles from the odometer. Don't rely on the car's trip computer and its calculations.

Do this, and then re-do your numbers. It's quite possible your mileage isn't declining at all. Or maybe it is. But this is the way to get accurate numbers.

Other than that, the things you mention are indeed critical - your driving style (avoiding hard acceleration, for example, and keeping a steady speed) and maintenance. Some of those maintenance items can have a big effect on mileage. For example, check the air filter even if it's not quite due for replacement yet. Also, one additional service item that isn't in the maintenance schedule but can help mileage is cleaning the EGR valve and ports.

Finally, you are saying that you used to get 18 mpg in mixed driving but now get 15 mpg. In my experience with my 2004 MDX, 15 mpg is pretty good. I've got all my maintenance up to date (including the EGR stuff) and I'm getting 14-15 mpg in mixed driving, and I don't drive overly aggressively. So maybe you were miscalculating when you thought you were getting 18 mpg, or maybe your driving mix back then was mostly highway miles with relatively fewer miles on local streets. (I'll get 18 mpg when I have a tank where my mix is mostly highway, and even higher than that, up to 20-21, on a long trip.)

[Crs]

Thanks nsxtasy, yes I have been doing my calculations by trip odometer divided by amount of gallons it takes to fill up. Also before I would get 300 - 315 miles per tank....... Now I get 240 - 280 miles per tank. It's just a little frustrating.

[G. COLTON]

Originally Posted by Crs

Thanks nsxtasy, yes I have been doing my calculations by trip odometer divided by amount of gallons it takes to fill up. Also before I would get 300 - 315 miles per tank....... Now I get 240 - 280 miles per tank. It's just a little frustrating.

This post does not read like you read the above very carefully.

George

[KES]

With 77,000 miles now on the MDX I suspect you are on your second set of tires. If so are they the OEM tire or another brand. I lost 1 mpg when changing tires from the OEM brand.

Your in Florida so I am not sure this applies but the winter fuel mix will impact MPG.

You may want to take it in and have Acura look it over to see if there is anything obvious (air filer, timing issue etc)

[Crs]

Yes, I am on my second set of tires. The original Michelin cross terrains were replaced at 65,000 miles with the exact same. I live in San Francisco Bay Area and right now the weather is in the 50's.

[carguy07]

Valve adjustment seemed to improve mine significantly.

[Crs]

At what mileage did you get your valve adjustment?

[nsxtasy]

Originally Posted by Crs

At what mileage did you get your valve adjustment?

In the recommended maintenance schedule in the owner's manual, Acura recommends a valve adjustment every 105K miles, regardless of time.

The recommended maintenance schedule in the owner's manual should be your guide to what to do and when. However, if you're concerned about your gas mileage, you may want to do the services that have the biggest effect on mileage more often than recommended. Those would be the air filter and valve adjustment, and maybe the spark plugs. And, as I mentioned, cleaning the EGR valve and ports, which isn't in the schedule.

So maybe you might not want to wait until 105K miles to have the valves adjusted, if you want to see if it improves mileage. Again, though, I seriously wonder whether you're going to suddenly get 18 mpg, since that's unusually high for mixed local and highway driving, in my experience, but you can give it a shot if you want.

As for the recommended intervals in the manual, some of the items need servicing based on mileage, others based on time, still others based on a combination of mileage or time, whichever comes first. Here are the recommended intervals for the most significant service items, according to the owner's manual:

• change oil and filter - every 7500 miles or 1 year, whichever comes first
• brake fluid - every 3 years regardless of mileage
• transmission fluid and transfer case fluid - first time at 45K miles or 3 years; after that, every 30K miles or 2 years, whichever comes first
• VTM service including differential fluid - first two times every 15K miles or 1 year; after that, every 30K miles or 2 years, whichever comes first
• coolant - the recommendation is 120K miles or 10 years, whichever comes first, the first time, and after that 60K miles or 5 years, whichever comes first. However this will be flushed (replaced) when they replace the water pump, and that will re-set your interval for changing the coolant
• air filter - every 30K miles regardless of time
• cabin dust and pollen filter - every 30K miles or 2 years, whichever comes first
• adjust valves - every 105K miles regardless of time
• spark plugs - every 105K miles or 7 years, whichever comes first
• timing belt (usually also includes water pump) - every 105K miles or 7 years, whichever comes first

[carguy07]

Originally Posted by Crs

At what mileage did you get your valve adjustment?

I think I was around 95k or so. I had the spark plugs done at the same time, but they still looked great. I picked up about 1 1/2 - 2 MPG.

[Crs]

I appreciate all of your input guys! I will post if anything changes with mileage.

[TheBigKahuna]

How much does a valve adjustment cost? I do them on my motorcycles, but wouldn't dare dive into the engine of the Acura.

[carguy07]

Originally Posted by TheBigKahuna

How much does a valve adjustment cost? I do them on my motorcycles, but wouldn't dare dive into the engine of the Acura.

I paid $250 at a local Honda dealer.

[PTC DAWG]

Drive downhill!

[fremaneler]

Your in Florida so I am not sure this applies but the winter fuel mix will impact MPG.