Inexplicable Gas Mileage Drop

Hi all!

I've had my 2007 Driftwood Pearl Package 2 Touring a little more than a year now. I had been getting 42-46 MPG every tank until I filled up my gas tank today.

Let me preface this by saying, I got my front tires replaced just 3 days ago. I filled my gas tank immediately after and that tank averaged 45.7 MPG. With that said, I filled my tank today (10.6 gallons which seemed abnormally high, but then again the last pip was blinking). I proceeded to drive around 40 miles the rest of day and as of right now, the MFD is displaying 33.7 MPG!!!

I think I'm going to drive about 140 miles tomorrow (mostly highway speeds), and I'll update this thread then. But as for right now, any ideas on why this is happening?

All comments and input is welcome. Thanks!

 

This may be, but it seems odd to me that this would happen immediately after recording one of my highest tanks to date.

Yes if I recall, he did say they were low rolling resistance, however, like I said, this is my second tank since I've gotten the tires changed and the previous tank was of near record proportions (for me anyway).

Tire pressure:

FL: 35 PSI
FR: Could not, for the life of me, get the cap off my just my fingers.
RL: 29 PSI
RR: 24 PSI

I'll inflate the rear wheels tomorrow and hope that that helps.

I did get my tires changed at Firestone. How do I check lug nut torque and what is considered "okay", if I can ask?

Thank you both for your responses!

 

Thanks for the number! I've driven approximately 450 miles on the new tires.

Currently the rear tires are Bridgestone Turanza EL400 (max PSI: 51) and the front tires are Bridgestone Ecopia EP100 (max PSI: 51). Before the fronts were changed I think I recall them both being Bridgestone Turanza EL400's. I'll try to inflate them and report back after I've been out and about today.

Thanks for the article... It was very interesting reading, as were the articles listed under "Most Popular Links."

Thank you both for your responses!

 

Just thought I'd update everyone on the situation. The 140 mile trip is happening tomorrow. But today I was convinced to resolve this issue.

The first thing I did was inflate all the tires to 35 PSI. I then proceeded to take it on a trip that was 40 miles roundtrip consisting of 55-65 speed limits and a few stop lights here and there. About 4 miles in, after watching the MFD readout holding strong around 34 MPG, I angrily pressed the reset button on the display.

For the remainder of the trip I got it up to 47 MPG.

Yet through this trip, I found something quite perturbing. When I would accelerate from a complete stop at a stoplight, no matter how lightly, the first couple seconds would read out around 5 or 6 MPG and steadily increase from there. I use the word increase loosely.

While looking at the Energy Monitor screen I found that the car seems to be charging the battery CONSTANTLY. Usually when you accelerate, it uses the battery power and the ICE, however it seemed to be using ONLY the ICE to move the car while simultaneously charging the battery, hence less than ideal gas mileage.

Now I don't know if this is actually what's happening or if it's just what the computer is telling me.

Since I arrived home after the 40 mile trip, I've taken it for a 2 mile trip and a 10 mile trip and managed to kill the MPG readout to around 43 MPG.

Just a bit of quick math here: I went 45 miles before pressing reset on the MFD and was averaging around 34 MPG. So with simple division, I would have, by those numbers, burned through 1.3 gallons of gas. After hitting reset I've gone 57 miles at and average of 43 MPG, burning, by these numbers, 1.3 gallons of gas.

So by those numbers, I've burned through 2.6 gallons in 102 miles, so 39.2 MPG.

But I would think that If I was getting such terrible gas mileage that it would have a negative effect on the gas gauge, but I still have 10 pips after 102 miles. And yes, I know the first one takes a lot longer to go away than the others, but I've had it go away in as little as 80 and as much as 125, but have never had such a terrible gas mileage readout.

Am I just obsessing? Could it be the battery? Should I take it to the dealer and have them run a diagnostic?


P.S. Sorry for the novel.

 

The 10 mile trip was mainly 45-55 MPH, stopping for a light once, average speed maybe 45 MPH.

I guess the proof will be in how many miles I get out of this tank... I mean if it's normal, which for me is about 380-420, I'll feel a lot better. It's just boggling my mind and I can't help but think something bigger is at play, but I'm just a worrier.

 

Thought I should update this thread.

Took the car for about 200 miles today. Managed to get the MFD to 45.2 MPG, which is fantastic, for me anyway. It's possible it just needed a long trip.

But those first 45 miles killed me. My gas gauge diminished to 4 pips. Despite all this, everything seems to be functioning properly.

Crossing my fingers for a normal tank (even slightly less than normal would be fine with me). Will update when I fill back up. Thanks everyone!

 

This intrigues me. How would I go about rebooting my car?