The O2 Sensor is a good cause of poor fuel economy, but not the PCV Valve [I don't think]. Pull your PCV valve. Shake it, does it rattle? If not, it'* time for a replacement, if it does, leave it alone. I believe there are two O2 sensors on your car. One on the rear header, and one after the Catalytic Converter. I would replace both, since it is good practice. However, I believe you can skip the O2 Sensor after the Catalytic Converter and nothing will really be affected. I'm sure we can all agree that it is a good idea to replace both.


-justin

Meh, same

Haro, quit driving 100+ on the freeway and you'll save money.


*edited by mod. Don't bash members. Subvertivly or otherwise*

haha....its all in great fun...

seriously though...i took a trip this weekend...filled up FULL in kato, drove to the cities and back, and then back to windom, so far its been 275 miles, and im at 3/4 tank...not bad for me

I get about 22 mpg on my '92 SSEi on a mix of city and highway driving.

When I want to check my current mileage, I reset the trip odometer to 0, fill the tank at pump A with the filler nozzle in the A slot until it clicks the first time, with the car in position A. Then I return to the same pump when I need fuel (the closer to empty the better) and fill up in the same way. I check the trip odometer and divide by the gallons indicated on the pump. Even being this careful, I cannot control factors like temperature and consequently how fast the pump is filling the tank. Different fill rates can make a difference in how effectively the air is evacuated from the tank and consequently how much fuel is added before the nozzle clicks.

Filling at another pump or using another pump nozzle setting, or topping up, or doing anything different can result in a gallon or more difference from the previous fill and really screw up the calculation. The fewer miles traveled when you make the calculation, the bigger the potential errors.

Of course, you can fill anywhere, any way, and if you keep track of your miles and gallons over many miles, you can calculate a very accurate AVERAGE mpg for your car.

Judging current fuel mileage by the gauge is often misleading as the gauges are not (as mentioned) linear. I have noticed that most car'* fuel gauges fall slowly from a full tank to 1/2, then drop progressively faster from 1/2 to E. This may be an accident of engineering but if so, GM has done little to correct it. I think this flaw is not addressed intentionally to make people think they are getting better fuel economy than they really are. Most people don't wait 'til E to fill their tanks, but fill when closer to 1/2. If they figure that 1/2 tank on the gauge is = 1/2 the capacity of the tank, their calculation for mileage will be WAY too high. By the time my Bonneville is at 1/2 gauge, I have used more than 2/3 of the tank'* capacity.

Example A: fill up at half tank on the gauge. 1/2 gauge (estimated to be 9 gallons) / 273 on the trip odometer = 30.3 mpg Damn good! Example B: fill up at 1/2 gauge (actually took 12.4 gallons to fill) / 273 on trip odometer = 22.0 mpg Not as good!

Just want people to know that using the gauge instead of the actual gallons can give some pretty misleading numbers. I apologize to most of you who already know this stuff, but I just wanted to help those who think their fuel gauge can be used to accurately calculate mileage.

I only average about 14mpg in my STE. I'm lucky if i ever get 200 miles to a tank. (16 gallon tank) It gets 24 on the freeway, but I do mostly city driving, and of course I "hotrod" it a little. Waiting for 3 minutes at a stoplight, and then driving a block and waiting again, and then driving a block and waiting again, does not help the mileage either. Someone needs to tell the dumbshits that set up the lights around here to time them a little better, and make them have shorter cycles. Its a small town, there isn't even much traffic. They also took all the 4 lane roads and cut them down to 2 lane roads with "bike lanes." That didn't help traffic either. I try not to go into town much because I can't afford it.

Shawn

did the 3100 swap help with MPG? and what are the gains from it?? can you do it to a 3.1 Multi-port N/A or 2.8 multi-port?

I usually get around 300 miles to a take. At one point I got 27 mpg on all highway driving, but now i'm lucky to get 22 out of the car ... I do need to do a tune-up, new o2 sensor, etc, but college tuition money comes first, then car

I did the 3100 Topend swap which is just the heads and up from a 3100 engine. It can be done to either a 2.8 or 3.1 MPFI engine. The swap would've helped with mileage, but didn't due to my cam and the fact that I haven't had the computer tuned for it yet, my car runs stupidly rich all the time. Before the swap I was getting 33mpg on the freeway now I get 24. On an N/A engine you're supposed to gain about 20hp, unless you do a cam then its like 30-35. I did the topend, a cam, and an UD crank pulley at the same time, and gained ~7 tenths and 5mph according to the G-tech. I still have yet to change my rockers to the 1.6 rockers (which should gain me at least another tenth) because I didn't want to put the extra pressure on the cam while breaking it in, but most change rockers when they do the swap. Also keep in mind that there are two different versions of the 3X00 topend, the '00+ 3100'* and all 3400'* have bigger intake valves and bigger intakes & tb'*. I used the smaller heads and intakes because thats what I had access to the cheapest/easiest, the bigger ones should give an even larger gain.

Shawn

I didn't read all the posts here, but the first one concerns me.

Our SSEi'* are capable of 29-30 mpg on pure highway, with the cruise set at 70. Mine does.