MPG decreasing - ideas why?

[kermit116]

The miles per gallon I'm getting on my 4 year old Volvo (65,000 miles) have gone down from 26-28 mpg to 22-24 mpg in the last week or two. I'm taking it for an oil change next week, and I'm guessing it might need a new air filter. Any ideas why the mpg would decrease?

I've been getting 26-28 mpg since I got it - it had 9,000 miles when I bought it. It's not a huge drop but it's bothering me that it happened suddenly.

I'm driving the same routes, using the same gas from the same gas stations, and driving the same way (no jackrabbit starts, not racing around).

I'm considering a new car in the next year so I'm wondering if this signals some problem with my car that I should worry about. Any advice is appreciated. Thanks!

 

[Jeff_G]

Is it hot outside? Are you using the air conditioning more? Also consider the possibility that you are getting crummy gas from your station... You might try a different station perhaps yours got a bad delivery...

 

[sam_gordon]

I was thinking air conditioner also. Tire pressure could also cause a drop. If you're not running your A/C, are you keeping the windows open at highway speeds?

 

[Mkebound]

Most likely causes:

Tires aren't inflated to proper presser

Air filter clogged

You got a bad tank of gas that isn't burning efficiently

You have buildup on the valves causes the pistons to miss fire or you have a bad spark plug causing inefficient fuel burn.

Something is causing drag on the car. e.g. the draft curtain on the underside of the car popped a rivet and is hanging down messing up the aerodynamics of the car

 

[mrodgers]

Clogged air filter, clogged fuel filter, dirty fuel injectors, spark plugs needing replaced, plug wires if you have them needing replaced, bad O2 sensor, many different sensors all over the car, did you get new tires that perhaps don't have as good of rolling resistance as the old? Bad gas as someone has already said. Has the gas station recently switched to 10% ethanol? Not everything is 10% ethanol yet, there are still some good gas stations out there yet....

 

[divabydisney]

Are you carrying anything heavy in the trunk or something that would weigh it down?

 

[Shelly F - Ohio]

Added weight in the car. If you are driving around with sports equipment in the car it adds weight causeing more fuel consumption.
Riding around with the windows down decrease MPG by 20% on the highway. Because it causes drag on the car because of the air rushing in and causeing negative force on the car ability to move forward.
Tire pressure and age of the tires is another factor.
Age of the car itself. Octane in the fuel you are using could be lower. I would switch to another gas company.
Transmission fluid may need to be to changed. Cooling system might need flushed.

 

[aceys_h0ney]

Have you had any work done recently that would have had the computer reset? I read that a few weeks ago that once the car's computer is reset it can take up to 50 drive cycles to get the same MPG you were getting before. Usually the decrease is small but noticable. I found this out researching for my boss who had the same issue but she had recently had her transmission replaced.

 

[bpesch]

Reports are that ethanol added to gas is resulting in all kinds of issues with cars. Decreased gas mileage is one of those issues. So if you use gas that has ethanol in it, it's a possibility.

 

[kermit116]

Thanks for all the great tips.

 

[disneymarie]

Watch were you purchase fuel too. How much do they add as ethenol? The past several stations had no ethenol and better fuel mileage. Tires properly inflated is another thing, check the wear.