19 Mpg? - Honda Prelude Forum

Emerson · 07-15-2008, 02:14 PM

Alright well I have been reading around and it seems people are getting alot more then 400 KM per tank. I have had the car a few months and run it to the empty light everytime and get 400 KM. I thought this was usual... But now im wondering there has got to be something wrong! No CEL no trouble codes. Air filter a little dirty, stock spark plugs+wires. Im thinking it's burning to rich, could an O2 sensor go bad without a CEL?

Mods: JDM Type S intake, Removed Resonator
Car: 1998 Prelude Base 5spd 61 xxx Km

thegamettt · 07-15-2008, 02:40 PM

your mileage is rather low for the o2 sensor to go bad, but yes it is possible. just replace it if you have the money, thats likely the problem. do a tune-up as well, you should start seeing better gas mileage.

Emerson · 07-15-2008, 02:42 PM

I don't really want to replace the sensor unless its actually bad.
Could a tune up really give me an extra like 100+ Km a tank?

elanx85 · 07-15-2008, 02:43 PM

I would check to see which fuel you are using. I'm pretty sure the car is designed to run 91 octane (US octane standard). I was getting an average of 25 miles per gallon whatever the conversion is on 93 octane gas in Texas.

thegamettt · 07-15-2008, 02:54 PM

well, my mpg dropped to 20-21, after i did it i got about 2-3 more per gallon?

Daemione · 07-15-2008, 03:42 PM

per tank mileage is next to useless . . . there is a wide margin for when the low fuel light turns on, and you can't bank on the listed spec of a 15.9 gallon tank (on a bone dry tank, I've never been able to get more than 14 in mine). So use your trip odometer & calculate an actual mpg (or kpg, if that's easier), and get back to us.

But to answer your question, yes, the primary o2 sensor can be "bad" without it throwing a code - causing lower fuel efficiency & hesitations. At your low mileage, I don't think it's very likely . . . but products like seafoam have been known to foul them.

For what it's worth, my SH still gets 28 or 29mpg on pure highway trips, but plummets to 21 or 22 during my commute (2 miles, 14 stoplights, all <40mph). You didn't mention what kind of driving you do.

Emerson · 07-15-2008, 03:50 PM

Yes its city driving
So how do I get an accurate MPG?
I know it has something to do with filling up the subtracting how much you used or something like that

thegamettt · 07-15-2008, 03:55 PM

set your trip meter to zero after you fillup. when you fill up again, divide how many miles you got by how many gallons you were able to put in. Also if you're doing city driving only in a prelude, don't expect much more than 20-22. city mileage sucks.

j0hnct78 · 07-15-2008, 05:23 PM

Just a shot in the dark, but do you have one of those whale tail spoilers?

Emerson · 07-15-2008, 05:35 PM

Nah those are for posers I actually removed the mast from a vintage sail boat and mounted it on the back of my car!! +Unlimited HP!! But seriously stock spoiler

rpwolf · 07-17-2008, 10:45 AM

theres so much you can do to get better fuel economy.
preludes best fuel economy range is between 2500 and 3500 rpms.
proper tire pressure. proper tire and wheel size.tune up.

your driving style is major factor.

Speed Stick · 07-17-2008, 11:19 AM

My o2 sensor went at about 80,000km except it kept setting off a code for me. Yeah that's weak mileage. I get 24mpg average. I drive it pretty hard in the city as well and I mostly do city.

98auto · 10-17-2008, 12:42 PM

I just wanted to say that after my 5 speed swap, Im averaging 27+ every tank!! Last night I hads 350 miles and put it 12.1 gallons of gas, for an average of 29mpg!! I can't believe it! I even had one tank at 30mpg!! I keep the tires inflated, I drive it easy, like an old man. Little or no vtec, windows up or sunroof open on the highway, and keep as little weight in the car as I can. The biggest thing is the acceleration. If you keep it easy and dont try and out accelerate the rest of the cars, you will be fine.

EX99 · 10-18-2008, 11:16 AM

Quote:

Originally Posted by thegamettt

set your trip meter to zero after you fillup. when you fill up again, divide how many miles you got by how many gallons you were able to put in. Also if you're doing city driving only in a prelude, don't expect much more than 20-22. city mileage sucks.

It's all in how you drive it. I'm able to get 25mpg city driving mine normally and when I want to grandma it the best I've been able to manage was 29.3mpg city. At the track however I only get 5mpg

That's exactly how I check my milage too btw, taking your tank to empty is difficult on the fuel pump. I generally try to fill up once it hits a 1/4 tank.

okieracer32 · 10-18-2008, 12:39 PM

The biggest factor for us in oklahoma now is that at most gas stations they are adding in 10% ethanol which gives you a 8 to 20% decrease in MPG make sure your gas is 100% unleaded and not blended.
So many gas stations were doing it here that they now require them by law to put a sticker on the pumps stating that it's up to 10% Ethanol.

I searched out a all gas no ethanol station and got an extra 72 miles per tank!

98auto · 10-18-2008, 02:18 PM

Wow! the ethanol "winter gas" is a huge scam. Just another way to squeeze money from consumers. I will have to watch my mileage especially now!

lukieluc · 10-19-2008, 05:27 PM

Quote:

Originally Posted by 98auto

I just wanted to say that after my 5 speed swap, Im averaging 27+ every tank!! Last night I hads 350 miles and put it 12.1 gallons of gas, for an average of 29mpg!! I can't believe it! I even had one tank at 30mpg!! I keep the tires inflated, I drive it easy, like an old man. Little or no vtec, windows up or sunroof open on the highway, and keep as little weight in the car as I can. The biggest thing is the acceleration. If you keep it easy and dont try and out accelerate the rest of the cars, you will be fine.

Same here!!! I get on average 27mpg, driving really slow and not going over 65mph EVER I get 29.X mpg on average. Its all in your tune up, what gas you put into the car, if you have windows open while driving, how much stuff you have in your car. also shift around 2500rpm

rhangman · 10-19-2008, 08:43 PM

366km from my last tank. About 48.3L (98 RON) from recollection so 13.2l/100km or 17.8MPG. I have done worse before.

rpwolf · 10-21-2008, 11:17 AM

Quote:

Originally Posted by lukieluc

Same here!!! I get on average 27mpg, driving really slow and not going over 65mph EVER I get 29.X mpg on average. Its all in your tune up, what gas you put into the car, if you have windows open while driving, how much stuff you have in your car. also shift around 2500rpm

you should read your honda owner manual sometime. they recommend at 3500 to shift. you might get better gas mileage.

also your windows down will only affect mpg when driving about +60mph depending on the aerodynamics of your car.

prepreludesh · 10-22-2008, 05:35 PM

RPWolf is right. The Mythbusters did a special on this where they drove a car at 45mph with the windows down for a full tank versus 45mph with the windows up and A/C on with a full tank on the same course and concluded that the windows down got better fuel efficiency.

Then a fan wrote in and questioned their test saying "yeah, but what about at higher speeds where wind turbulence could affect a car with windows down more?" So they went back and did the same test keeping the car at 55mph and concluded that the air conditioning got better gas mileage!

In my opinion, I don't know why nobody here has recommded getting their car an alignment. I actually get my car aligned every 3 months (by necessity) because the roads here in el paso suck. Coupled with my lowered suspension (i.e. a really stiff one) it really transmits all hits and vibrations right into the suspension and then to the car rather harshly. I have to wonder if this is the reason my alignment gets out of wack so easily. But if your Toe is off, that could be a major factor in low MPG because imagine pushing a shopping cart where both rear wheels are facing inwards and how much harder it is to push that car in a straight line versus if they were perfectly straight ahead (in which case the only thing slowing the cart down is the natural friction between a moving item and the ground instead of something trying to go one way but the object dictating it goes another). You see what I'm saying?

Alignment FTW!