Did you lower the car around the same time as the tires? If not yu shouldn't need and alignment unless you hit something. Same size tires? Maybe air pressure is low or the new tires are significantly heavier than the old ones?

 

Nope, just changed the front tires.

One of my front tires popped, so I was on a temporary spare. The spare (front passenger) was 235/35 while the front driver tire was 225/35

 

I posted in one of the other threads, but on my 2006 stock IS350 on strictly highway driving on the way back from picking it up I averaged 32 MPG. With a mix of day to day city and highway driving I'm averaging closer to 24-25 MPG

 

I wonder if a small change in octane can affect fuel economy. Where I used to live I had the privilege filling up with 93 octane, but now i'm forced to used 91 octane.

 

Not unless there's something else wrong with the car, no.

The car is programmed for 91 octane...anything higher doesn't help at all. (though anything less is likely to hurt and the car will be pulling timing to fend off engine knock)

 

Will mpg improve as engine breaks in? My 350 with a few hundred miles has gotten at most 24 with mixed driving

 

wow these number are great i have a 10 250 and i maybe get 20 or 21 mpg but then again 80% of my driving is city, so i end up getting about 320 to a tank ifthat much

 

I just recently did a trip from Cedar Creek to Arlington, and Arlington down to Dallas on one tank. There is about 60 miles of city driving in there. That was driving between 70-80 mph mostly. I filled after I took this picture and filled up 15.53 gallons (let the pump stop on its own). That calculates to 29.36 mpg; pretty close to the indicator.

 

Small variations in driving habits can have a massive impact on MPG.

In my 250, I recently I went on a trip (3.5 hours each way) in hot weather, and had the A/C keeping things frosty inside and I was going between 70-80mph most of the time.

My mpg reading on the computer was 32-34 MPG most of that time. It would go higher on the smaller back highways where I was forced to keep speed around 60mph.

My daily average is probably around 26-27mpg because except for travel I tend to drive in short trips.

I've had fast cars in the past and got tired of the wear they put on brake pads and tires, plus the gas mileage. This car gets about 20% better mileage of any car I've owned that had a 3.5 litre V6, and will fare about the same against a 350 under same driving conditions... but that's the key and the hard part to prove scientifically -- same driving conditions. Cars with more horsepower naturally lend themselves to a faster driving style, so real-world results don't always reflect what's possible.

My last car was a Maxima with a 3.5 litre. I thought I was doing good if whenever I saw 25mpg in that car. 21mpg was probably average if you drove the car the way it wanted to be driven. You could get 25mpg with lots of highway driving by going easy on it.

 

I typically drive 60% highway and 40% city so get around 29MPG combined (Around 420ish miles a tank).

Evenever I fill up, the approx range is somehwere between 440-450. I go 60mph on the highway with the cruise control on and I try to keep my RPMS under 2500 in the city.

 

I took a roadtrip to Orlando this past weekend and got 430 miles on 13.2 gallons of gas which ends up being 32.5 MPG!

I could have kept going to 500 but I didnt know how far the next few rest stops were and didnt want to run out of gas

 

Going home from Reno to Oakland to San Jose, about 275 miles

 

Go 60 and see what you get

 

i dont understand how the 350's are getting more MPG than i am with my 250. im not flooring it or anything. i drive at a moderate pace and dont do any extreme maneuvers either and my avges say 18/23.

 

High beams and dirty looks because I'm holding up traffic?