I have a 98 5sp. Its been getting around 15 mpg in the city. Is this normal? Gas prices have been going up and if there is anything I could do to make it better I need to do it soon. Gas is to expensive to be wasting. The car only has an intake on it, nothing else.



Thank You
Kenny

 

I also am having problems with my gas mileage. I have had 18's on my car this summer and my gas mileage was on average 230 to a tank. I took my rim off the other day and with stock 15's I get about 380 to a tank.

 

well now you know why a stock max came with those rims instead of 18".

As for 15mpg, you just gotta figure its one or all of your oxegen sensors or Knock Sensor. Also might wanna see if it needs a tune up or a new fuel filter, air filter and clean your Trottle body.

 

Check you ECU for ghost codes.
That would be the first thing you need to look into.

If you have 0304, (Knock Sensor), then that would be a big reason for poor mileage.

(Technically a high flow air filter will increase (better) you gas mileage.)

If you have no codes / ghost codes, then look into other possible reasons.

dave h.

 

ok. sorry, but this is a sort of off-topic question for dave harms or any other. i see the statement alot, but it doesn't make any sense to me. for a high-flow air filter, more air means more fuel is needed to keep the A/F ratios proper. so if more fuel is needed, how does that equate to better gas mileage???? is this not right? someone please help me understand

 

bigger rims = worse gas mileage ?????????????????
what the he** ??
why? because the car is heavier with 18" ?

 

Somethign liek that..since the rims are heavier, the gas mileage will be worse. I also have 18's and my gas mileage is horrible, im not saying its the rms fault totally, but it does make a difference. Also make sure you have the correct air pressure in teh tires.

 

bigger the rims and tires the more revolutions the engine has to turn to turn the tire. This is why the speedometer becomes inaccurate when you increase the tire/rim size. Also wider the tire the torque and power required to turn it on the ground increase, which means your engine is working harder thus requireing more fuel.

 

there ya go

 

how do u know if ur knock sensor is goin' bad?

 

but should I be losing 170 miles to a tank from larger wheels and tires?

 

u get a ghost code in ur ecu, if u check codes u will get 0304 or u can use a multimeter to check it, the multimeter way can be seen in my sig for the ecu codes link or the 3rd link on the sticky "help check engine light is on" on both look for 0304

 

Thanks for the help. But how do I check the ECU codes? Do I bring it to a shop and ask them to check it? I do have the 2K1 SE rims on the car. How much difference can that make?

 

I remember seeing that for each 1 lb of additional weight per wheel/tire, it is like adding 3 lbs of weight to the car. This has to do with rotational mass or something like that. Also look at the fact that the odometer may be off if the overall diameter is not the same (you could be traveling further than odometer is measuring, which will make gas mileage appear lower). Also add in added rolling resistance and aerodynamic drag of wider tires (hey, it all adds up).

For the original post, check the items like others have suggested. Check ECU for codes, especially knock and O2 sensors. If you get both, I'd replace O2 sensor(s) first, clear ECU, and see if the knock sensor code comes back (it sometimes appears because another sensor is bad). It may not, in which case you can save about $130. If the knock sensor code appears by itsself, it is most likely bad. Either case you can test it with a ohmmeter.

Dave

 

to check click the link of the sticky that says "help my check engine light is on"