Thread: Jump in Gas Mileage

In a mix of freeway and around town driving, my car's been getting around 17 mpg. I've been very disappointed with that considering how I've been babying it, but hoped it would improve as the engine broke in. Upon mpg meter reset, I might start out in the low 20's, but over the next 100 miles with mostly surface street driving, the mpg meter would migrate to the high 16's to low 17's. My car now has about 1100 miles on it.

Well, with 1100 miles, I decided it was time to see what I could expect in terms of acceleration when I might need it. So, I got on the freeway, dropped the speed to 40 mph, then gave it an ass-blasting up to 85 mph. It is a spirited car. Repeated the sequence a couple more times, then got off the freeway to return home.

As I was driving home on surface streets, I noted the mpg meter bump UP one notch. So, I continued to drive around for several minutes, and it bumped up another. What the ??????????

That night I gave it another couple ass-blasts, then reset the mpg meter. With nothing but surface street driving, the mpg meter's now staying in the high 19's. Go figger.

I see two possibilities here:

1. With the wee-wee thin 5W-20 oil in the engine, the stress of the hard acceleration opened up the connecting rod bearings. Frankly, I doubt this possibility.

2. The fuel metering computer need a final reference point (hard acceleration and higher rpms) to start working correctly. I'm hoping this is what happened, and hope it continues to hold true.

I have yet to do a freeway/highway only trip to determine what the highway mileage is going to be. Still might be too soon in the break-in process to make that determination anyway.

Needless to say, I'm a lot happier right now. Hope the feeling lasts. Has anyone else experienced anything like this?

I too have experienced some poor MPG the first time I owned my Azera, though it had 4,900 miles when I got it. Explained in another thread, 60-70% my driving in a given week is highway, but I do frequent side roads, back roads and some traffic lights in small towns. I originally started out at about 23-25mpg, but I feel as if I adjusted to the car's gear ratio, and have thoroughly enjoyed my average weekly MPG of 27. I did notice that the first 100-150 miles in any given "trip" sets the tone for the MPG the rest of the gas tank, assuming all future driving on that tank is pretty normal.

I drove back from Penn State and it was about 150 miles. I ended up averaging 30.2 mpg, crusing the highway at 74 or 75mpg. I traveled to work a few times before filling up, any I ended up with 30.1mpg for the last 500 miles. I think that the mode/terrain of driving really sets the tone for the MPG you will see on any given tank run.

The best mileage I've seen in strictly "city" driving was 21mpg. But I had to seriously drive like a grandpa. Using the manumatic, not letting the RPMs get over 1500-2000, upshifting as soon as it will let me, and popping it into neutral for a long coast up to a light or a turn let me get this. It hit as high as 25 at one point. Keep in mind though, that where I live there are lots of 45-55 mph roads with minimal stops unless I really get into town. This is just way more work than I want to do though, so I'll be going back to driving normally and getting 17 or so in town.

On a side note, I did drive a couple of thousand miles using premium, just to satisfy myself if it made a difference. It didn't. 26.5 mpg highway. Back to the cheaper stuff!

Originally Posted by IRingTwyce

On a side note, I did drive a couple of thousand miles using premium, just to satisfy myself if it made a difference. It didn't. 26.5 mpg highway. Back to the cheaper stuff!

I was going to check this out (knock sensor retarding timing?), but now I won't bother. Thanks for the update.

Welp, I've now got 4500 miles on the car. Mileage has continued to slowly improve. Now, I'm getting 18 rather than 16 mpg around town, and 30 mpg on the freeway at 70+ miles per hour. First oil change at 4200 miles to 10W-30 from the factory fill. Did not notice ANY decrease in mileage with the slightly thicker oil.

Regards, Gary in Sandy Eggo