my p5 has a bad fuel consumption. what are the possible cause?

W

wertyguy

Member
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mazda protege5
I am getting frustrated from p5. Im not quite sure if I have sliding clutch. At 100 kph my p5 has a rev of 3k in 4th gear automatc. That is too high, im not sure if that is normal? I also checked if I have fuel leak but there is none. Could it be my air filter? What are the possible cause? My tires were fine too. As I remember at 90km of driving I already consumes 4 lines in my fuel gauge. I dont know if that is normal. Please enligthen me.
 
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first, the fuel gauge is horribly inaccurate. to get a good idea of fuel consumption, you need to fill the tank completely, run through a full tank, then refill completely. take the amount of miles (kilometers) driven for the tank and divide by the amount of fuel to required to refill the tank.

second, if you have the automatic transmission, not much you can do - it sucks for fuel economy. also, no clutch with the automatic.

last, 3000 rpms at 100 kph (~62 mph) is very normal for this car. heck, i have a 2011 miata with a 6-speed manual and i'm turning 3500 rpms at 70 mph! no need to worry, since the car was designed for this use.
 
I have a 2003 Automatic. Downloaded an App for my iphone called Mileage Keeper and this is a screen shot of mine. I'm averaging 23.3 and im not all that aggressive when driving.



 
just fyi since i use miles you use kilometers and so forth 1mpg= .425 km per liter. or 28.7mpg= 8.2L/100km for conversion purposes

the automatics suck on mpg, i get from 24-32 or 33ish mpg(depending how i drive it)with mine and its a manual. approximately 3k rpm is what mine does in 5th (overdrive or your 4th gear) at 65ish mph (or about 100km per hour in your units) i live way south of you in texas and its warm here most of the year and i get from 25-31 or so average most of the time but if temps are around 45 or lower it takes the car longer to warm up and the systems this car has in the intake make it rev considerably higher(only when its cold outside) while it warms up which i know lowers my mpg in those lower temps and i get 24-27ish mpg about 28 max average if i am careful or drive more freeway than usual in those lower temps. these cars get much better mpg on freeway i can get 39-42 on a straight freeway shot.

use fuelly.com to track your mpg its easy and lets you see your average mpg your average cost per mile and per tank as well as letting you see overall and monthly/ last 10 fill up fuel mileage. also lets you see many other aspects that can help you get better mpg. (click the picture in my signature and it will link you to my fuelly page and let you sign up there)
 
The biggest culprit to fuel economy is tire pressure. Just because they look alright, doesn't mean they are at the correct pressure, 32 PSI is what our cars are rated for.

Driving conditions affect economy as well. For us in Canada, we see a difference of up to 2L/100km between seasons and thats because of snow resistance and winter tires, albeit, thats on the Caravan.

Whats the history of maintenance on the car? If you don't do regular oil changes, air filter changes and new spark plugs once in a while, your economy may suffer.
 
wertyguy said:
,... Could it be my air filter? ...
Click to expand...

Yes it could,.. My mileage went up 3-4 MPG after changing my dirty air filter.

Here's the big list,... (air filter is first on the list.)

fuel_zps9598eb5d.jpg
 
pcb said:
Yes it could,.. My mileage went up 3-4 MPG after changing my dirty air filter.

Here's the big list,... (air filter is first on the list.)
Click to expand...
yes change it if your just going to check it as its worth it to do at least once a year (except k and n or cleanable ones) and if you dont know the last time it was done its easy and cheap fix. i would consider cleaning your mass air flow sensor and throttlebody as well. this can help dramatically with fuel economy. there is a seafoam thread around here somewhere but basically let the car warm up, shut it off, take the vacuum hose off the brake booster, start it up and slowly pour in about half a can of seafoam while its idling (it will idle horribly and try to die while doing this but its ok) make sure you dont kill it doing this as that takes away some of the effect. shut the car off and reconnect vacuum hose to brake booster.pour the rest of the can of seafoam in the gas tank. let the car sit at least 2 hours then go drive it kinda hard it will smoke alot at first but thats the seafoam cleaning it up. keep driving til it stops smoking and then a little more and that should help dome as well, its helped my car.
 
I'm having trouble with my fuel consumption and I'm hoping there's something to do to return it to what it used to be. First things first, the engine was just rebuilt. The original engine blew up a month after I got it and the replacement JY engine was eventually burning a quart of oil every 100 miles. Brutal.

Anyway, at its peak MPG performance, I hit 34 MPG while throwing a code for EGR flow. Funny. Normally, I would hover in the early 30s. When I started taking the highway to work rather than back roads, I dropped down to 28 (while burning tons of oil.) I blame the weak 5th gear for this. My last tank on the rebuilt motor yielded 24 mpg. I'm wondering if this is a break-in sort of thing that I have to wait out or if there's anything obvious to take care of.

I've recently 1. rebuilt the engine, 2. replaced the coils, plugs, and wires, 3. cleaned the EGR and idle air controller, and 4. replaced the knock sensor. I am going to replace the fuel pressure regulator because it triggered a CEL. I may have to also replace the fuel filter because my idle hiccups below 500 RPMs once in a while. Looking at the list above, it couldn't hurt to 1. change my air filter and 2. do a seafoam treatment through the vacuum lines. Is there anything else I should look out for and either clean or switch out?
 
RBFIRE said:
I'm having trouble with my fuel consumption and I'm hoping there's something to do to return it to what it used to be. First things first, the engine was just rebuilt. The original engine blew up a month after I got it and the replacement JY engine was eventually burning a quart of oil every 100 miles. Brutal.

Anyway, at its peak MPG performance, I hit 34 MPG while throwing a code for EGR flow. Funny. Normally, I would hover in the early 30s. When I started taking the highway to work rather than back roads, I dropped down to 28 (while burning tons of oil.) I blame the weak 5th gear for this. My last tank on the rebuilt motor yielded 24 mpg. I'm wondering if this is a break-in sort of thing that I have to wait out or if there's anything obvious to take care of.



I've recently 1. rebuilt the engine, 2. replaced the coils, plugs, and wires, 3. cleaned the EGR and idle air controller, and 4. replaced the knock sensor. I am going to replace the fuel pressure regulator because it triggered a CEL. I may have to also replace the fuel filter because my idle hiccups below 500 RPMs once in a while. Looking at the list above, it couldn't hurt to 1. change my air filter and 2. do a seafoam treatment through the vacuum lines. Is there anything else I should look out for and either clean or switch out?
Click to expand...

if there are copper spark plugs in it check the gap.
 
RBFIRE said:
I've recently 1. rebuilt the engine, 2. replaced the coils, plugs, and wires, 3. cleaned the EGR and idle air controller, and 4. replaced the knock sensor. I am going to replace the fuel pressure regulator because it triggered a CEL. I may have to also replace the fuel filter because my idle hiccups below 500 RPMs once in a while. Looking at the list above, it couldn't hurt to 1. change my air filter and 2. do a seafoam treatment through the vacuum lines. Is there anything else I should look out for and either clean or switch out?
Click to expand...

I would change the filter and pump before touching the regulator, I have never heard of the regulator going bad on these cars.

RPMs might be dropping because of a bad EGR, common issue on these cars, the little motor rusts and malfunctions.

Good idea about the air filter, but I don't see the point to seafoam if your engine has been recently rebuilt.
 
In the fall (when I bought it) i was getting about 28mpg with a mix of highway and city (70% highway maybe). Right now with winter gas and winter tires and BRUTALLY cold temps here and all short trips, just based on the gauge, I have gone about 185km and the needle is at half a tank! Yikes.

My air filter looks good. I have not checked the tire pressure lately - I suspect I need air as the temps are a lot colder than before. I have new copper tipped plugs waiting to go in. Is there a sign that the plugs are bad by just observing the car behavior?
 
davemsc said:
In the fall (when I bought it) i was getting about 28mpg with a mix of highway and city (70% highway maybe). Right now with winter gas and winter tires and BRUTALLY cold temps here and all short trips, just based on the gauge, I have gone about 185km and the needle is at half a tank! Yikes.

My air filter looks good. I have not checked the tire pressure lately - I suspect I need air as the temps are a lot colder than before. I have new copper tipped plugs waiting to go in. Is there a sign that the plugs are bad by just observing the car behavior?
Click to expand...

Make sure you check tire pressures, it is critical for consumption.

ReginaldWagon said:
I concur with big_dill, check the EGR valve and see if it needs cleaning.
Click to expand...

It is a pain to remove, but just 2 bolts after the intake is off. There is a shaft with a valve inside that should be moving smoothly, if it doesn't, then the EGR is bad. It is right under your throttle body.
 
The_big_dill said:
Make sure you check tire pressures, it is critical for consumption.



It is a pain to remove, but just 2 bolts after the intake is off. There is a shaft with a valve inside that should be moving smoothly, if it doesn't, then the EGR is bad. It is right under your throttle body.
Click to expand...

Yeeeeah, to me that is greek lol.

What would it cost to get mazda to check it out and/or replace?
 
The_big_dill said:
I would never go to the stealership. But its simple enough to trust a local mechanic IMO (if you can't do it yourself.

Here is a guide on how to do this: http://www.mazdas247.com/forum/show...o-EGR-Removal-and-Cleaning-for-Rough-Idle-Fix
Click to expand...

This guide and the whole thread are awesome but doing this recently, I cannot stress enough how bad the screws are. The bolts are taken out easily enough with a tiny ratchet and shallow socket but the screws... They wanted to strip without any pressure at all. We had to take a torch to them and pull them out with pliers.
 
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