tire size on 94 civic HB
 

I have a 94 civic HB 1.6 5speed. It currently has 175/70/13 tires and I was thinking of putting on 14" or 15" when it is time for replacing them. My commute is 110 miles per day all hyway. i currently get around 40 MPG at 70 plus mph. I know this is too fast but it is a long trip. Any thoughts?

It depends on the style of wheels you get, if you get some "racing" wheels that are more like egg beaters then anything else and weigh more then stock steel wheels you might never see a mileage increase, but if you get something like civic hybrid or Honda Insight wheels that are pretty flat and smooth then put a tire like the Low Rolling Resistance Bridgestone Potenza RE92 tires on there, then you should see an increase in your mileage.
Whatever tire you choose, make sure it's a Low Rolling Resistance tire.

Since you are on the freeway it will probably be worth it.
stock is 165/70/13 weight 14lbs 22.2 inches in dia. 949 revolutions
...........175/70/13 weight 15lbs 22.7 inches in dia. 927 "
...........175/70/14 weight 15lbs 23.7 inches in dia. 886 "
the 14" tire is 7% larger in diameter. above 5% will show mpg improvement

Make sure the larger rim is not too much heavier

Check to see if there is a shock or strut tower that would limit how tall you can go.
For example:
I have the tallest tire that fits up to the bottom of the front stut tower
http://i678.photobucket.com/albums/v...PG/tiregap.jpg

tirerack has outer dimensions of a bunch of tires, including diameter.

Thanks for the responses. I am now leaning towered 175/65/15. There is more choice in with this size. I am looking to get a set of stock aluminum wheels that a hot rodder is discarding, there are lots of tuned compacts in my area. Lug pattern is 4x100mm, common to lots of small cars.

I just found a set of 4 205/60-15 Perelli snows on Ford Escort aluminum wheels for around $250.

im going to be replacing my 175/70/13's with 195/50/16's just because i have a set laying around. the difference is about 1" diameter but it is wider so i probably wont see a fe impact for the better.

your moving a lot of weight (relative) to the outside of the diameter.
That is going to wear out suspension parts sooner,......

I have 14 inch wheels and am now tire shopping. My primary goal is to reduce noise at high speeds. My second goal is to increase millage. ride handling and price are also factors.
I am trying to decide between 185/ 70 and 185/75. The 185/ 70 will give me the minimum decrease in rpm that I am looking for 7% the 185/75 will give me 10%.
here are some questions;
Will the 75 have horrible effects on handling?
Are Lrr more important in stop and go as I read on a manufacturers site?
Is weight a major concern if I am 95% highway?

Weight is going to have a larger affect for your stop and go driving and it's going to have an affect if your roads in your area are bumpy or full of potholes.
Low Rolling Resistance tires help any time that the car is moving.
In my hatch back I noticed a great improvement in handling when I went from a heavy set of 175/70 R13 tires to a lighter set of 165/70 R13 tires, even tho it was only a few pounds less per tire and 10mm narrower the whole car felt lighter and more responsive.