well, today i taught the gf how to calculate her fuel economy by dividing the number of miles she drove since she last completely filled up by the amount of gas she had to put in the car this time to fill it up. she did the math and says 13 mpg. well, i think this must be wrong, but she was right. only 13 mpg. thats crazy! i mean, isn't the 95 SSEi rated for a little better than that? i thought its supposed to be low 20'*!

ok, so i'm guessing that there must be something wrong. where do I start trying to get it running more efficient? it has a new air filter but i'm assuming original plugs at 59K. any suggestions are appreciated!

that is not the right way to calculate mpg.

ok, so how do you?

thats the way i've been doing it forever and it seems pretty accurate.

oh, and thanks for not answering the question. if you aren't going to be part of the solution, then just stfu.

I used to fill the tank. run it down then divide the miles traveled by the number of gallons I filled the tank with. For example my 95 Honda Civic 320 miles divided by 9.5 gallons (10 gallon tank) equals 33.6 mpg. Thats right about where the EPA said it should be. My 96 Bonneville'* window sticker says 19city/30hwy. The EPA changed their testing process and have downgraded the car (1995) to 17/26. I am averaging 24 mpg (90% hwy) doing the math the same way as my Civic. My unsientific tests are a combined average of city and highway. I looked at the 1996 Bonneville on the EPA site and they seem to only list the supercharged engine as the page shows it requiring the use of premium fuel.

Look it up at Fuel Economy

Dean

it'* wrong because it'* inaccurate.

here is how you do it:
1. Fill up your fuel tank and write down the odometer reading from your speedometer.
2. Drive the car until you need to fill the tank again. Let it go down to about 1/4 of a tank or less.
3. Fill the tank again and record the odometer reading and the number of gallons it took to fill it. Be precise; record the gallons exactly including the portion of a gallon usually represented by a decimal in hundreds of a gallon. For example 15.78 gallons.
4. Subtract the previous odometer reading from the new one to determine how may miles you have driven between fill-ups.
5. Now simply divide the miles traveled by the number of gallons used. This will tell you how many miles-per-gallon you are getting.
6. For example let'* say you went 356 miles between fill-ups, and it took 15.78 gallons to fill the tank. Well, 356 miles divided by 15.78 gallons equals 22.56. So you got 22.56 miles-per-gallon on that last tank of gas.
7. Check your miles-per-gallon over four or five fill-ups to get a good cross section of different driving conditions such as city, highway and so forth. Then take all your calculations and average them out (add them together and divide by the number of calculations) to get an overall picture of your gas mileage.


this is a much more accurate way of doing it.
either way you should be getting better mpg.
do a tune up!



please don't tell me to shut the **** up. act like an adult even if you are only a child. we try to make this a friendly welcoming place and by telling members to shut the **** up it'* not helping AT ALL. If you continue to be rude and tell me or other people to Shut The **** Up i will alert the moderators and they will deal with you as needed. most likely it will result in a ban. i'm not trying to scare you i'm telling you how it is. play nice little one. also, if you even thought for a second about how to do it accurately you would have come upon the solution right away. instead you decided to lash out at me for no reason and be rude to boot. Try thinking and using your brain next time and also try not to swear and insult me as it hurts my feelings deeply.

thank you for coming in today!

i said that because it seems that every forum that I see that you have posted in, you always are good at making some rude or insignificant comment that has nothing to do with the question or comment and you have a tendancy of doing it in a very hostile or blunt way. In my other thread, you were already warned by a moderator for your behavior and i think its ridiculous that you continue to not offer any assistance in answering people'* questions. I'm just saying that you need to step away from the keyboard when you have nothing to say or don't "feel like" typing out the correct answer. Its a forum- people come here for solutions and to discuss their love of the bonneville. you aren't being much of a team player by putting people down and replying with rude comments. all I ask of you is that you try to stay on topic and reply with relevant answers to questions or simply say nothing at all. so, really, I feel that I have done nothing but point out the obvious.

good day to you.

to get back on topic, thank you to everybody who answered my question about why my mileage is so bad. i'm planning on running a bottle of fuel injector cleaner through the car and a spark plug change in the near future. hopefully that does the trick.

Ok, let me step in here. Yes, 13 MPG is way low. At the next fill up reset the tripometer, Then the fill up after then devide the miles on the trip by the gals. This will give you a general idea. After 3 or 4 fill ups you will have a much better idea. Now that we have that out of the way here'* what you need to do to improve your MPG

First, the right foot is evil nd is the biggest problem. So light on the foot. Next, fill with premium gas only. Yes, it costs more but you will get 2 or 3 more MPG which off sets the extra cost. Avoide ethinol if possible. Change your spark plugs to 1 temp range cooler and gap at .055. Check to make sure your wires are in good shape. Now for teh thing that will help the most. Get a new O2 sensor and replace it. DO NOT use Bosch. They simply do not work well in our cars. Auto Parts Fast at RockAuto has some great prices.

My 97 gets a bit over 25 as long as I keep my foot off the gas. With a REAL good tune, you can get around 30. But if you can get low to mid 20s your doing good.

ok, thanks danthurs! its prolly getting horrible mileage because she runs only regular or midgrade because her dad said that it was ok ( i know its not but she listens to her dad more than me) and also her plugs are original from 1995. Also, the way you check your fuel economy is the same as the way I do (i just didn't go into such great detail in my first post) and I would have never thought to check the o2 sensor. How do I know if the plug wires are bad? visually, they look ok and have no cracks or anything...

Change the plugs, go with autolite copper the 605 is 1 range cooler and cost under $2 each. If you see no damage on the plug wires, they should be OK, But a new set wont hurt. Stock wires are fine, don't let anyone tell you you need these really good wires. Plug wires are plug wires.

As for the gas. Normal NA engines run fine on regular gas. But this is a supercharged engine and the pressures are much higher. So it runs better with premium and you will get a few more MPG.

As for the O2, That should be replaced every 60K or so. You wont throw a SES code unless it fails totally. But O2s tend to die slow and take millage with them.

If you have a club member near by someone may be able to help you out. They can be a pain to remove. Where about are you located?