My best commute mpg ever ... why!?

Weird.

I got a huge spike last night, and in my HyHighlander. I am not sure what cause this, short but sweet MPG:

 

I get about 49 mpg driving in cities.

 

From what I've read on the boards here, it seems around the 5k mark the engine breaks in and you start to begin to see better gas mileage. You could be figuring out how to drive the car as well. Quite a bit can come into play. I'm surprised your down around 40's though. Are you taking all short trips or going way over the speed limit? Could be alignment as well. Heck I'm a new prius owner too and drove 70 mph from the cities to see what kinda mileage I'd get and it was still at 50.2 over 80 miles. Not sure what your doing wrong with getting 40. Keep plugging away though!

B

 

Hi Ichiro,

The Oil Change and alignment are most likely the causes. The initial oil put in at the factory is a special formulation for breaking in the engine. So, its probably higher viscosity. Additionally, if it was much above the top dip stick mark, there might be a little mileage hit from that. If the refill is now standard 5W-30, and 1/4 inch below the top dipstick mark, that will help a bunch. Let alone, that the oil run for 5000 miles in a new engine is going to be loaded up with fine materials from the break-in process.

When my car was new it was acceptably stable on the highway. I drove back in mild winter winds from the dealarship 484 miles. No problems. If you had problems with trucks pushing the car around in an uncontrollable fashion, it was probably an alignment issue. Which might result in more rolling resistance.

The new tire would cause your mileage to be less. The new sharp edges on the rubber have higher rolling resistance, and the side walls do not flex as readily on new tire.

 

I am just wondering what happened to your tire.

I tend to get nice mpg numbers right after an oil change. Keep your speed at posted speed limit and you'll see your mpg improve.

 

it's a new car. why wouldnt the dealer give you a matched tire?

 

I asked this question previously because when we drive south from Sacramento to Bakersfield, we had about 8mpg better fuel efficiency on the way down than on the way home.

The consensus from the forum was that a subtle tailwind did the trick (which turned into a headwind on the way back).

So, maybe you had a tail wind and didn't realize it.

 

Wait until you hit about the break in at about 30,000 miles.