Ok ... my gas mileage kicked *** when I first bought my MP5. I was getting close to 310 miles per tank. I put on 18" OZ F-1 Racing rims on it, and it dropped by like 30 ... went down to about 270-280 per tank, and I also installed the Nology Hotwire conversion kit at the SAME time, note that is the only engine "upgrade" I have done at this time. Well the last time I filled up I was only at 210, so that means my gas mileage dropped an extra 60 or so miles, and the only reasons I could come up with were
1. bigger rims are harder to get moving
2. more powerful spark due to the wires
3. spinning out in rain a little bit (very rarely though)
The problem is, that I am confused as to why it could have dropped so much because it was gettin about 280 after the rims but then it went down an additional 60 for NO reason at all. Any help?

 

By the way, one last thing I forgot to mention. When I bought my car, it was a salvage, it came with a little "problem". The only thing that was wrong with it was that the door panel was screwed up because someone broke into it, but the problem is that the check engine light was on. The car only had 3500 miles on it, I got it for 10g about 3 months ago and have put on about 4000 miles on it. The thing with the check engine light is "insufficient EGR flow" is what they told me ... well first of all I'd like to know what EGR does, as my car runs just fine the way it is now, and could this problem finally be starting to kick in and cause my car to consume more gas?

 

Those Nology plug wires didn't do you a lick of good, did they? I say, ditch 'em. And, 210 miles out of a tank is awful (provided you do a lot of highway driving). If that is all you are getting, I would say that something is wrong with your car.

EGR stands for "Exhaust Gas Recirculation". What it does is introduce exhaust back into the combustion chamber, which does two things
1) Leans out Air/ Fuel mix
2) Lowers combustion temperatures (to limit oxides of nitrogen, aka NOx).
EGR also improves fuel economy, by about 1~2 mpg in normal driving in my experience. If you don't have EGR, you will consume more fuel. But the amount that you are suggesting is unrealistic unless there is something else going on.

Are you sure that you are only getting 210 miles per tank now? Did it get worse, or did you change your driving habits (city/ freeway mix)? How empty are you letting it get between fill ups, and are you accurately accounting for the fuel remaining in the tank? And, finally, why don't you average it over say 5 tank fulls to make sure this is a realistic number?

 

Well my driving habits are the same, I do about the same highway and city driving. And from the time I posted the thread and the time I am posting now I used up about an eight of my tank and I only went to my class and back which is about a 15 mile drive one way ... so a total of about 30 miles. This didn't start happenig until a couple days ago, when half of my tank just simply disappeared. I always fill up when the light comes on, and since the last time I filled up, last night, I've gone 64 miles and it's already almost to the quarter line. I agree, there must be somethin wrong but WHAT?!?!?!

 

i have the nology's and 17" wheels along with a few engine mods and i still get 31mpg out of it, did you change you plugs as well

 

Yep I sure did. The Nology wires aren't it ... I know that for sure. Because I've had them in for a month or so now and I only started noticing this huge decrease about a week ago. I know the 18's contribute to it, as well as the cold weather. I just went out and checked the air filter and it's just fine so that's not it either. The EGR has been messed up all along and that never seemed to cause much of a problem either, so I truly have no clue what it is. Maybe our cars just really really suffer due to cold weather.

 

How long do you run the engine for in the morning to warm up the car. That is a lot of wasted fuel. You don't drive anywhere but you're still using gas.

 

I start driving as soon as I turn it on ... and honestly how much gas can you consume while idling?

 

I experience about a 20% drop in gas mileage (31 => 26 mpg) when I discovered my rear tires had developed scalloped inside edges due to wheel misalignment during a tire rotation. After a 4-wheel alignment, my mileage recovered.

 

I was getting ~29mpg highway and after 4wheel alignment getting ~33mpg. I also noticed a little difference when I removed the roofrack.

 

Alright ... well thanks for the help guys. But I still think there's somethin else goin on with my car. I'll try putting my stock rims back on and seeing if that makes a difference, and if it doesn't then I'll just have to blame it on the cold weather or something .. because as soon as it started gettin cold as hell it started using up more gas. That doesn't make much sense to me ... but since there's no other explanation for it so far it'll have to make sense ... I think?

 

hey krayziefox i have the same problem too on my mp3 which should b about the same my gas meter goes from the very top of the meter n just drop like 3 lines down after about 20 miles i was wtf... i started getin this problem about a month n a half now so i really dont no wats wrong n i HAVE do grandma drivin or when i start off or ill waste a crap load of gas i dont no y.. any help here? o yea n check ur tire pressure taht might help n ur air filter to n make sure its not dirty

 

Krazie, I think it's possibly because your AC compressor is running.
If it's getting colder, or rainy, and you use any combination of defrost/floor vent your AC compressor will run. As soon as I realized this was happening I stopped using the defrost
except when necessary, it made a big difference.
And I never use my a/c unless my wife is in the car bitching about the heat!

 

Is it bad that im getting 22 mpg.
I got 17's and the mazda speed axelback on.
Im convinced that the exhaust is whats causing it because I now fill up weekly while before I would fill up every week and a half -two weeks.
I think its time for an alignment that should help, Im also working on a hyperground, that should help me out, too.

I would also like to point out that I have the 1.6l and that most of my driving is highway miles, it might just be time to trade this thing in for a more effiecent GTO or something, dam this lead foot.

Ill be filling up tomorow hopefully I get better news, or ill have to start doing stuff.

 

I commute 45 miles each way, mostly highway. I suggest approaching this methodically. Go thru the usually culbrits in order of cost:
1.) driving habits; avoid rabbit starts and heavy braking as much as possible.
2.) check tire pressure. I run about 30-32 psig to maximize my gas mileage
3.) improve aerodynamics; remove roof racks, bug deflectors, door vent shields, these all add drag (i.e. wind resistance)
4.) add some fuel system cleaner to next tankful
5.) spark plugs; regap, or if older than 35k-40k miles, replace them
6.) air filter; hold element over a trouble light to see how dirty. If dirty (black - little light showing thru), or more than 30K miles old, change it.
7.) wheel alignment; again misalignment means more drag and more power (fuel) to overcome it.
8.) have fuel injectors checked; dirty clogged or dead injectors are detrimental to mpg. Some mechanics have system to extract and test flow from each to assure they are roughly the same to each cylinder.
And yes, gas mileage does decrease (~5% or 1 to 2 mpg) with colder (near or below freezing) air temperatures.