Universal O2 Sensor and tire question

[following]

Over in the "Introduce Yourself" forum, Ryland suggested that I put different tires on my 92 Civic CX and Matt Timion suggested a new O2 sensor.

Can anyone help me to understand why the 155/80 tires would be better? As Ryland guessed, I do have the 175/70 tires. I'm new to understanding how everything affects mpg -- any tutoring/apprenticeship would be happily received...

Also, I'm looking into getting a new O2 sensor at Matt's suggestion. The CX has 186k miles and looks like not much has been replaced. Rock Auto has a Bosch OE type for $205 and a universal for $21. Any reason not to go with the universal? I've got a relative who is an excellent mechanic and especially skilled with electrical components who could help me with the universal.

By the way, I'm having great fun driving the CX and got 37.5 mpg on my first tank (with a flat tire in the trunk, using AC, and old O2 sensor).

[ezeedee]

155's are skinnier, so they have less rolling resistance, so you dont have to use as much energy to maintain speed.

universal o2 sensors dont have the OE connection so you have to cut the oem plug off and splice the wires together. for that price difference, id def go with the universal.

[Telco]

Check with the dealer on the O2 sensor, get a part number, and see if you can order one online. Universal O2s are the same as the jack of all trades. A universal is set to work on multiple vehicles, so its operational parameters are looser and it is not as efficient as one made for the vehicle. Mileage and performance won't be as good as it could be. Not to mention, I usually find myself replacing Bosch O2s after about a year when the sensor goes lazy. After a couple of these replacements, I stopped buying them. Go with a factory replacement, and it'll last several years and net the best mileage.