Increasingly Poor MPG
 

I own a 2006 Mercury Mariner Hybrid with approximately 68,000 miles. When I first got the car it was not uncommon for me to get about 28 MPG in the city and 30+ on the highway. Absolutely loved driving it.

Over the last couple of years my MPG has slumped to the point where I'm now getting 20 MPG in the city and 22 on the highway. I perform regular maintenance on the vehicle and am baffled as to what the problem could be.

Recently the MECS pump failed and I had it replaced at the local Lincoln dealer here in Savannah. When I dropped it off I explained my MPG problem and asked that they provide some insight after looking at the car. They fixed the pump and said that all systems are running correctly. Basically, they had nothing new to offer.

I should point out that I have been told that my battery is weak and will need to be replaced sometime in the coming months. That said, I do not see the connection between MPG and the battery, so I have not considered this a contributing factor.

Any information on what I can do to try to improve my MPG would be appreciated. Thanks!

John

Re: Increasingly Poor MPG
 

The battery will affect MPG through speed of charging and discharging. As cells get older, they have less "elasticity" (for lack of a better word) and take longer to transmit, receive, or retain electrons. The batteries have a shelf-life of about 7 years, and they are warranted for that same period of time. If it IS your battery, get in there and get it replaced under warranty before that expires.

I have a 2008 MMH AWD with 75k miles and I still have great summer mileage. Things that will affect your hybrid mileage quickly are the freshness of your coolant, gunk in the fuel injectors, and tire pressure/alignment/camber. My MPG had dropped from 38 when I bought it to less than 30 in April due to balding tires and aging fluids. After a $200 series of transmission/oil/coolant flushes and fuel injector treatments, as well as a $800 set of new all-season off-road tires... I'm back to 32mpg in the summer. (Had I gone with street tires instead of off-road capable, I'd be much higher fuel economy.)