As of about 3 weeks ago I have noticed a drastic drop in my MPG. Usually I am able to get between 85-95 miles per quarter tank (5 gallons). I am now lucky if I get 70 miles per quarter tank. The only thing that has changed is my tires, I got NEW ones. I did go from some old squared out FireStone Firehawks to General GMAX (215/55/17). I have a K&N Typhoon intake in the car and I plan on cleaning the filter this weeked, it does not look very dirty nor does much dirt come off when touched. I run 93 octane gas and my driving habits have not changed. I just recently hit 60,000 miles and was considering a tune-up but am not sure if that is the issue/if it's worth it.

Any ideas?

 

did you change tire size? This can affect everything about your cars mileage and even cause the speedo to read 'off'. check this against the GPS built into your phone.

 

No that's the stock tire size, and to make sure there wasn't a huge discrepancy between the tires actual gas mileage I checked TireRack's road tests and there was only a 0.4 MPG difference in the Firestone and General brand.

 

Where do you live? If you're in an area with oxygenated fuel you'll definitely see a decrease in mileage during the winter months.

 

I live in NY, but I don't remember seeing this much of a drop off last year when it got colder, is the tune-up something I should be considering at this point since I am at 60,000?

 

Get some maf cleaner and clean your maf. K&N filters are known to get them dirty.

 

This^^^

I would also replace your plugs and PCV valve and make sure your tires are at proper pressure.

 

Did the plug change and MAF cleaner but still had poor mileage in my X... Did a simple PCV valve change and it jumped up 2 mpg! Guess that was the culprit!

 

I'll try the cleaner and monitor it and then proceed with the rest of the options you guys have given me so I dont have to spend too much time in the cold attempting to replace/fix parts lol.

 

60K miles is pretty early to start needing to do tune-up items like plugs and such. I'm at 112K on my '06 and just recently changed my spark plugs and it gave me a 1-2MPG increase.

My first thought it winter blend fuel, but i haven't noticed my MPG drop much since the changeover.

You said you have new tires, check to make sure they are properly inflated. With the onset of cold weather, tire pressures tend to drop and running low can make mileage suffer.

Any check engine light on?

Have you calculated out your fuel economy by filling the tank, driving it, then refilling and dividing the gallons added vs miles driven?

Our fuel gauge is not that accurate. It's slow to move inthe top of the scale, and then drops like a rock near the bottom, so it's hard to give an accurate estimate based on 1/4 tanks and such.

 

Check out the thread here.

It seems that there are numerous potential causes for bad MPG.

There is even someone there that gets 24mpg mixed with a Turbo installed. So essentially, the mileage is all over the place with our cars.

 

My tires are properly inflated, no check engine light at all, car seems to be running the same. I always check my mileage with miles driven vs gallons used to top off, I generally get between 20-21MPG and I just filled up today and I averaged 16MPG.

 

The PCV replacement only takes about 15 minutes and I believe the valve is less than $20 so you might do that when you clean the MAF sensor.

 

Ok, I will go buy a PCV valve today to replace when I clean my MAF. Stupid question, where is the PCV valve?

 

Look at the bottom braided hose from the catch can that goes to the left side of the motor. It connects to the PCV valve. So front left of the motor in this pic.