2007 Low MPG -- Can't figure out why

Hi F8L,

I usually check them about once a month. I expect air loss as the temps get warmer and if we have a warm spell then a cool down, I'll definitely check them since I know that'll cause a pressure loss.

Really? Hmm, I'll have to give it a shot. I think I'm only daring enough to go to 40/38 though. EG Toyota recommended that I keep the tire pressure the same on all 4 tires. Their reasoning was that because we have a toddler, a car seat, and cargo associated with him, we should add the extra 2 psi to the back tires to compensate. What are your thoughts on that? I can see doing that on our LA trips since we're usually pretty loaded down with luggage, but the rest of the time?

Yes, some of my best mileage on LA trips was because I was daring enough to go slower (or traffic was nasty enough that I got out of the left lane and used the right lane more to avoid the constant speed up and slow downs between 55 and 85). My best mileage going to LA was 48 MPG, that was going 75 with a tail wind. Another time when I had a tail wind, I used it to my advantage and did 80 and still pulled off about 46 MPG.

Given the fact that I have traveled between Sac and LA several times a year for the last 5 years, I know what to expect for my mileage, even worst case, and 36 was WAY too low so I knew something was wrong.

 

Hi Richard,

Thanks! I think I will give it a shot (and I do check my tires once a month).

Before, in September. I ran the pressure in the old tires pretty much the same as now, about 38/36.

My tires still had some tread left to them. EG Toyota and America's Tire had both recommended to me that I replace them earlier last year, but I decided to wait until just before my October trip to replace them (and just before the winter weather).

I don't know, I'm a little weary about grill blocking. Isn't the upper grill where the air intake is? Or is it the lower grill?

Interesting. I think I can count the number of times on one hand that I've used Chevron and if I remember correctly, my mileage was not as good with them. Maybe its the additives? My use of Shell stems from convenience and that they are the lesser evil of most oil companies.

I have to respectfully disagree. I've driven in cold weather with lower than normal tire pressure (for me, that would be lower then 38/36) before and I still managed around 41-42 MPG.

As for the new tires, I wouldn't think they'd contribute to such a significant drop in MPG.

 

Hi all, after driving my car last night, I think uart is on to something when he mentioned the battery fan. Last night, I was observing the behavior of my car more closely as I was running errands. I made a few stops at stores and I noticed that after starting the car, it was behaving normally and the electric motor would use power from the battery to help accelerate. However, after a minute or so of driving, the electric motor would stop using battery power to accelerate and would rely solely on the engine or charge the battery pack, while accelerating! If the pack is starting to get too warm because the fan is clogged or not working, I can see how the motor would stop using it to accelerate.

When I got home, I ran the car around the block in EV mode, so that I could try and get the battery fan to come on. After that, I put the car in park and put my ear next to the battery fan inlet and didn't hear anything. I also tried listening for it from the trunk. Nothing. I'm beginning to wonder if it's clogged or just stopped working. Thoughts?

 

Wow, I did not know that! It makes sense though. Thanks, I'll try running 40 psi and see how that effects my mileage when my car starts behaving normally again.

 

If I understand you correctly, your thinking is that the charge in the battery is low when I started the car? If that's the case, I can tell you that it wasn't. The charge level was at 6 bars (top of the blue range) when I observed this behavior. It's similar to the kind of odd behavior I noticed before but this was the first time I noticed the car doing what it's supposed to, albeit briefly.

 

Ah, got it now. Thanks!

 

Hi all,

I'm trying to add the images that were in my original post. Hopefully this will work. The first image was taken while I was driving on flat road. The second was on a hill. Notice the behavior of the car and the state of charge of the battery?

Flat:


Hill:


It should be noted that it was at that state of charge the whole time I was on the freeway and was NOT the result of going downhill. The car would deliberately charge the battery up to that level.

 

Re: 2007 Low MPG -- Can't figure our why -- Update

Hi all,

Ok, so yesterday, I opened up the battery cooling fan and was able to determine that it was not the cause. The thing was virtually spotless, just a little bit of dust. I went ahead and blew it out with a can of compressed air (the kind you use on keyboards and such) before putting it all back together. I got half way through putting the trunk back together before I realized I hadn't taken a picture, so I hope y'all will believe me when I say that it was pretty dang clean.

My next step will be to order the 12 V optima battery. I've already looked around but it seems like I have to order it online. Is that the case or has anyone been able to find it in a auto parts store like Autozone or Kragen?

 

Yeah, that's what I figured I would have to do. Did you order straight from Optima or did you get it from an online retailer (ie Amazon, buy.com, etc)? I hope it resolves my issue as well.

There are no such things as silly questions!
The trip in November was very windy. One of the reasons why I took so long in coming to the conclusion that something was wrong was because I attributed that trip to the nasty weather. However, the trip back was rather calm and balmy but I still got sub 40 MPG. Then I recalled a previous trip with crazy winds and cruising at about 75ish and my average was still around 41 MPG, not 36! I was floored by that! Also the December trip, which was pretty calm and mild, registered at 33 MPG! As I think about it, it would make sense that the 12 V is dying. I can see how on longer trips constant 14+ V charging would cause the charge level to go down while the shorter trips around Sac wouldn't really show as much charge depletion.

Yeah, I think I'm going to start inflating them to higher levels now. I'll probably just start with 40 psi on all four tires (I'm not daring enough to go higher yet ).

Nope, nothing on the roof. Gave some thought awhile ago about adding a receiver hitch for a bike rack, but decided against it. Ever since my son was born, my bike riding has gone down to practically non-existent. When he's older, I might pick it up again so I can bike ride with him but I'm hoping I won't need the receiver hitch and that something better will be out there (I expect I'll have something different like the Prius V or plug-in Prius anyway).

 

Wow! That is pretty dang low. I haven't started the car for a few days so I'll have to see what the current voltage level is. It has typically been around 12.0 V. I re-read Richard's 12 Volt battery thread the other day and noticed that his specs called for 12.4 - 12.8 V at startup and 12.1 V at ig-on. I think I'm below spec based on his thread but not as low as 10 V!