jmack: take note of your coolant temp when you drive it next. If it shows less than about 210, then change the thermostat out.

 

How long does it take to replace one o2 sensor? Also how long to replace both sensors?

 

On a lift, with the proper tools, it takes a few minutes each, Lying on the ground, with the front up on jack stands, in the snow, using nothing but a claw hammer and a crescent wrench, you should be able to knock them both out in an hour.

 

How many o2 sensors are on my 98 blazer 4 door LT 4wd?

 

If I remember correctly, you should have two sensors.

I had to replace my rear one several years ago. Now I'm wondering if I should put replacing the front one on my to-do list for the spring!

 

I saw a video on YouTube where someone said there are 3 o2 sensors on a 2002 blazer. I don’t know if that would be the same as on my 98.

 

A few things I've noticed that affect my mileage:

• In town driving I'll get 11 or 12 at best. In the winter I get down towards 10. I then found this link that has a lot of reasons why mileage is lower in the winter: https://www.fueleconomy.gov/feg/cold...Dmile)%20trips.
• Axle ratio. If your axle ratios are on the lower end, e.g., mine is 3.73:1, then you will get worse mileage than the ones with the higher ratios like 3.08:1.
• 4wd vs 2wd. 4wd vehicles will always get worse mileage than 2wd. First there is more weight to move with 4wd and then if you are using your 4wd, then that uses up engine power. This is especially true if you have one of the Auto-4wd systems.
• Larger tires. This is more of a math problem in that larger tires will have the effect of the odometer showing fewer miles than you actually drove.
• Luggage boxes. I saw my mileage drop when I added a Yakima Rocket Box to the top of my Blazer to hold my recovery gear.

 

Thank you all for your assistance. I will let you know what I try and if it works.

 

Thanks for that! My Blazer just got 1 mpg extra. That's $8 a month saved ;-)

 

There are three O2 sensors. One for each side ahead of the single catalytic converter, and one after the single catalytic converter.

If your fuel trims are normal, and your front O2 sensor voltages are cycling across 0.45 volt - then your front O2 sensors are reading fine. Rear O2 sensor just checks catalytic converter function for the PCM.

These vehicles can really have some poor mileage in the Wintertime. I have seen the 11 mpg on mine around town before in the Winter with warming up and stuff and 4WD. Agree with the 14 mpg city during the Summer. Max of 18 mpg on the highway on a level road.

Sticking brake calipers are one thing to check though and they can really kill gas mileage. Another thing is how you drive - a lot of people don't realize that slow easy starts use much less gas than does fast acceleration. Keeping steady speed (not riding someone's butt) is another thing that helps mileage. Another thing is wind resistance - slow down - pushing a brick through the air at 60 mph is a lot easier than at 75.

My advice ...... be happy it runs good. Don't buy a Blazer if mpg is your expectation. They are not known for it.