Awful Gas Mileage

B1GHAM said:
the only fuel filter in the proteges is INSIDE the gastank. There is no inline filter.

one thing only 1 person has touched on is winter blend gas. Winter blended gas will usually yeild slightly lower gas mileage, although it should only be about 2 mpg at best. Where do you live? this might help us figure out other issues.

Also, cars do like to "breathe" everyonce in a while. Try going out after the car is warmed up and really romping on it for a few minutes. Doing so will help blow carbon deposits from the cylinder walls and exhaust system. Yes its fine to ride around shifting @ 3300 rpm however you will lose some performance/gas mileage due to deposits of carbom.
Yes winter gas has increased ethnoyl levels to keep it from freezing, which in turn lower you gas millage. Ive seen more then 2mpg decreaser using that s*** in my cars. Also cold weather plays a role allround as well. Basically in winter you millage will be alot worse then in nice weather.
 
P-Funk! said:
I still coast to a stop when practical and i don't tailgate (speed up slow downspeed up slow downspeed up slow down).

Coasting to a stop versus maintaining speed and then slowing with the brakes - bet you can't measure the difference it causes in mpg. A couple of years ago I tried coasting to a stop versus braking on my drive back and forth to work. There as no difference that I could see. This was in a manual 323 sedan.

Either way you're bleeding off the car's kinetic energy as heat, just in different parts of the car. The RPM are lower while you're coasting down than if you maintain speed, but you will coast for a longer time, so it tends to cancel out. Or looking at it the other way, you'll never burn less gas with the motor running than when you're idling. So if maintaining speed then braking gets you to that light to idle more quickly that may burn slightly less gas. Not enough to measure though, at least when I tried it.


As for tailgating, it probably does save gas on the highway. At those speeds there's a lot of wind resistance, and tailgating cuts that down. It's also dangerous as hell which is why it's illegal.
 
i know i got 230 miles on my last tank...i thought i was the only one...its actually making me mad cause ive been trying to drive like a grandmah
 
230? What the heck? I just emptied my tank from full and the odometer trip counter was at 302 miles. Which, if i am correct, the car has a 14 gallon tank still puts me at about 21-23 mpg. Not the best, but, better than 10mpg that my Jeep gets.



My honda gets the best milage. I get bout 40mpg if I am easy on the throttle




But, it's got 2 less wheels than you guys.
:)

Tylor
 
cbrjeeper said:
230? What the heck? I just emptied my tank from full and the odometer trip counter was at 302 miles. Which, if i am correct, the car has a 14 gallon tank still puts me at about 21-23 mpg. Not the best, but, better than 10mpg that my Jeep gets.



My honda gets the best milage. I get bout 40mpg if I am easy on the throttle




But, it's got 2 less wheels than you guys.
:)

Tylor
i know...it baffles me...ever since winter hit
 
well guys...my turbo'd auto...last tank mix of city/highway...got 28mpg...if your getting less than that you've got problems...dirty air filter, low tire pressure, bad gas, dirty egr/iac...there are a number of things that could cause so poor mileage
"There are a hundred factors which can cause poor gas mileage. One of the main causes is a dirty air filter. Low tire pressure, bad driving habits (lead foot syndrome), transmission torque converter clutch failure, transmission slipping, stuck choke plate, leaking injectors etc. etc. etc. Most of these factors will normally result in poor performance as well. " from bob's auto repair page
 
Hey guys,

Mine is a manual. I live In Nova SCotia, but the winter has been crazy mild here. No snow yet!

It is frustrating since you can actually see the needle move down. Right now, I am on the 1/4 mark left, and just went over 300km....187miles!!!!!!!!!!!!!!!!!!!! WTF!!!!!

Whether it is winter gas or not, this car should get better mileage than that. I mean, I see commercials for v8 trucks that get about the same!!!

It is really disappointing. I do love the car, but this is just stupid.

I have 5w30 in it. Air filter looks great.

ugh....i have only had the car 4 months and thoughts of getting rid of it are in my head.
 
bradicus18 said:
you will actually get worse mileage by "topping off" your gas tank. it is the way cars are designed now that they burn off the fuel vapors in the tank as well to increase the mileage. i don't really understand how it works that well, but it is something to that effect. someone else will know for sure

You get slightly worse MPG by topping off - but only because fuel weighs ~8.9lbs per gallon - so you have more weight you are dragging around.

The fuel pump draws liquid fuel only from the bottom of the tank. This is what goes in the engine. You also have a tank vapor recovery system to burn off vapors (instead of venting them) but the impact on MPG is negligable at best. It is only for hydrocarbon emmisions.
 
newprot5fan said:
Hey guys,

Mine is a manual. I live In Nova SCotia, but the winter has been crazy mild here. No snow yet!

It is frustrating since you can actually see the needle move down. Right now, I am on the 1/4 mark left, and just went over 300km....187miles!!!!!!!!!!!!!!!!!!!! WTF!!!!!

Whether it is winter gas or not, this car should get better mileage than that. I mean, I see commercials for v8 trucks that get about the same!!!

It is really disappointing. I do love the car, but this is just stupid.

I have 5w30 in it. Air filter looks great.

ugh....i have only had the car 4 months and thoughts of getting rid of it are in my head.

Nice to see someone else from nova scotica on here :D

I just calculated my MPG, I got 26! thats on 91 octane gas, but its bad winter gas, nice and cold here and im not used to driving the car yet, i would say about 90% city and 10% highway.
 
pasadena_commut said:
Coasting to a stop versus maintaining speed and then slowing with the brakes - bet you can't measure the difference it causes in mpg. A couple of years ago I tried coasting to a stop versus braking on my drive back and forth to work. There as no difference that I could see. This was in a manual 323 sedan.

Either way you're bleeding off the car's kinetic energy as heat, just in different parts of the car. The RPM are lower while you're coasting down than if you maintain speed, but you will coast for a longer time, so it tends to cancel out. Or looking at it the other way, you'll never burn less gas with the motor running than when you're idling. So if maintaining speed then braking gets you to that light to idle more quickly that may burn slightly less gas. Not enough to measure though, at least when I tried it.


As for tailgating, it probably does save gas on the highway. At those speeds there's a lot of wind resistance, and tailgating cuts that down. It's also dangerous as hell which is why it's illegal.

Let me be more clear... I meant if i see the light turning yellow ahead - i don't stay on the gas and then hit the brakes - i am already coasting. Idle burns less gas than staying on the throttle longer... And saves brake wear as well. Watch the idiot who goes screaming by and then wails on his brakes! sigh.

Drafting a truck on the highway? Sure! But i didn't want to include it here - DON'T DO IT (This message from my lawyer). Drafting a car won't gain you a significant amount - and like he said is too dangerous to contemplate (my lawyer agrees :))

Lastly - keep you tire pressure at the correct mfgr psi. More than that does save gas - but costs you tires!
 
P-Funk! said:
Let me be more clear... I meant if i see the light turning yellow ahead - i don't stay on the gas and then hit the brakes - i am already coasting. Idle burns less gas than staying on the throttle longer... And saves brake wear as well. Watch the idiot who goes screaming by and then wails on his brakes! sigh.

I hear you. I'm just saying that the difference between:

1. Cruising at 35 mph. The light turns yellow 200 yards out so you take your foot off the gas and coast to a stop.

and

2. Cruising at 35 mph. The light turns yellow 200 yards out and you continue to cruise for another 50 or 100 yards and then stop using moderate brakes.

in terms of mpg, is negligible. Try it one way for a couple of tanks and then the other way for a couple of tanks more. If you can see any difference in mpg I'd be amazed. Well, maybe on a manual if you coast by shifting into neutral, on an automatic there are all sorts of drive train losses in drive even with the accelerator all the way up. Agreed the brakes will last longer if you go with (1). In S. California though if you're coasting down from 35 mph that far from a light the next car is likely to crawl right up your butt and may hit you. Especially since your brake lights won't be on.

The clear winner here is regenerative braking, in which case one drives like (2) and the energy is stored instead of wasted. Not an option on the P5 though.
 
Haven't sat down and calculated my mpg. I'm working on that this tank.

However, I'm wondering, would 17" wheels with low profile tires lower gas mileage significantly? That's how I bought my P5; it has its stock wheels and all-season tires, but I haven't gotten around to putting those on -- plus, I'm guilty for liking the way my car currently looks.
 
pasadena_commut said:
It will change the calibration on your speedometer/odometer and perhaps
make it appear like you are getting different gas mileage. To compare before
and after you'll need to normalize by that factor. There's a calculator here:

http://www.miata.net/garage/tirecalc.html


^^^now there's something that slipped my mind...definitely could be part of the mileage issue...

and put some more air in your tires...32psi is the most common air amount but with 16"s you should have a little more in there...my winter tires have a max of 44psi but I run them at 34-36 or so instead of 32, check your tire to be sure and don't forget to rotate every three months or so.

I don't have a mileage issue with mine, never have...but I know it burns more in the winter anyways...cars in colder climates do in general but 20mpg seems oddly low... as I've read over this thread, you've checked your filters, plugs, etc, the only other things I can think are possibly a bad O2 sensor or your knock sensor.

Often times it's not just one thing causing the problem (although we all wish this to be so).
 
just posted this on another page...


I noticed something funny tonight that I must share with all of you. my tires "felt" under-inflated recently so I drove to a gas station and went straight to the air hose. The air hose has a built-in pressure gauge that pops-up when you press it to your tire's valve as you all already know. The pressure on the gauge read 30 PSI. Just a tad low. I then pulled-out my Accurite digital pressure gauge and WOW...it read only 22.5 PSI. I wasn't sure which was correct, but I was banking on the accurite. I inflated my tires to 33PSI on the Accurite. The gauge on the air hose read over 40PSI. I don't know how that can be, but I checked it with a third (non-digital) pressure gauge that I own and it confirmed my Accurite's readings. Basically, it can very well be that people are inflating their tires using the hose's pressure gauge and are therefor under-inflating their tires which is contributing to poor gas mileage in the winter time. I realize that dividing by 14.5 gallons is incorrect (as you've pointed-out), but it won't increase my MPG by much. In any case, the tire pressure seems to be my main culprit and after filling-up tonight, I am anxious to see what my result will be. I always fill-up until the pump stops and then re-set my Trip counter. Then see how many km until my gas light goes on.... I'm sure there's something else wrong somewhere... Will re-setting my ECU actually do anything like some of you have posted? Thank you all. Go out and buy a digital pressure gauge...WORTH EVERY CENT!!
 
Weborific said:
Basically, it can very well be that people are inflating their tires using the hose's pressure gauge and are therefor under-inflating their tires which is contributing to poor gas mileage in the winter time. I realize that dividing by 14.5 gallons is incorrect (as you've pointed-out), but it won't increase my MPG by much. In any case, the tire pressure seems to be my main culprit and after filling-up tonight, I am anxious to see what my result will be. I always fill-up until the pump stops and then re-set my Trip counter. Then see how many km until my gas light goes on.... I'm sure there's something else wrong somewhere... Will re-setting my ECU actually do anything like some of you have posted? Thank you all. Go out and buy a digital pressure gauge...WORTH EVERY CENT!!

This is a gas station's way of making you fill up more.

To (pretty) accurately calculate your gas mileage, fill up your tank until it auto-stops (the pressure is pretty consistant). Drive until whenever, and fill it up until it stops again. Divide your miles by the # of gallons needed to fill the car up. Usually this is around 11.9-12.2 for me. 330mi/11.89gal is pretty typical for me (27mpg).

Resetting your ECU will give you bad mileage until your car "learns" itself again. After that, your mileage should be better. This usually takes a couple tanks of gas. Alternatively, you can wait a few months and it will learn by itself.
 

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