Low MPG?

[MrsZR7]

Since I've had my '03 P5, I've replaced the coil packs and plugs, air filter, I run sea-foam with almost every tank of gas, and most recently, I had a fuel system service done at a shop.

I was told that I could expect a great increase in economy after the fuel system service, but I'm not impressed. I've gone through almost a full tank of gas since I had it done a week ago, and only got 25 MPG.

So I know there's another component of the tuneup that I haven't done yet - an O2 sensor or something?? How hard would that be for a newb to tackle? I'm a female newb, who doesn't have a ton of mechanical knowledge, but I'll dig into a minor project when I get the chance.

 

[zhy]

24mpg here
*brofist*

yea definitively check for o2 sensors
maybe get a mp3 ecu reflash and run premium gas, you'll get more mileage for your money too.
UNCLOG YOUR EGR VALVE too. :3
(subscribed)

 

[Bastian]

Honestly 25 MPG is about right with these cars, if you drive like a normal person doing mostly city driving. I typically average around 21-24 MPG, but I deliver pizza.

 

[Hank3]

OP - do you have an AT or MT tranny? Most AT owners get lower MPGs and are pretty much in line with what you're averaging. And with a MT, unless you drive like a grandma (i.e. shift under 3000 RPM, light on the throttle, coast to stops), you won't get that much higher MPGs.

I average between 28-30 MPG in the city and 32-34 highway.

 

[JiggaBro]

i have a MT and according the an app that ive been using for the past 12 fillups, im getting 19.6 mpg

Mods that contribute to mpg: AEM sri, UDP, axleback



then again i drive it like i stole it!

 

[lostmybook]

If you drive with average acceleration and have an automatic AND driving mostly city, then that does sound right--though it could be ~2 miles more per gallon IMO. IF you have a manual, drive mostly highway at around 65mph, then it should be around 30mpg. The latter example is my driving situations: mostly highway, 65 mph, averaging 30-31mpg.

Also, are your tire pressures in spec?

 

[Flash5]

My car is averaging 27.5mpg and thats with a full exhaust and intake. In the winter i average around 26 and in the summer its around 30. It also depends if you have an auto or not. You gotta remember this car is around 10yrs old and rated at 24city 28highway, so don't expect anything huge.

 

[SoCalMP5]

25 avg is right on the money. There's nothing wrong with your car based on MPG alone.

I get 25-26 city (accelerating slowly and shifting around 2600-3000) and 29-30 highway if I'm easy on it. An ALL highway tank, with the cruise set at 65, will get me a solid 30 to 30.5 mpg avg for the tank (we're talking no city/stoplight driving except to get on and off the freeway).

This tank I'm revving it a little bit more to see the differences. The torque peak is 4000rpm, so I think shifting at 2500 or under like some people do might be worse overall.

'02 manual, all stock, 80k miles, in good tune.

These are decent numbers if you put it into perspective. My modded 5 cyl car gets about 14mpg city and 19mpg highway. The P5 feels like a hybrid to me. lol.

Don't Seafoam it that often...there's no reason to. Once the buildup has been cleaned off, the Seafoam isn't doing any good. If you drive the car easy (you never floor it or race it or drive aggressively), go to a lighter than OEM synthetic (run a 0W-20 at your next oil change) if you haven't already. Make sure your tires are always filled to max PSI. And coast as often as you can if it's a manual.

After that, if you really want better mileage, you have to start modding the car.

 

[digitalslacker]

Its all in how you drive. Wintertime will net you less MPG. I do a decent amount of highway and according to fuelly am getting 29mpg average over the last 26,000 miles.

https://www.fuelly.com/driver/rat3idea/protege5?fu=2219921

 

[MrsZR7]

I thought I heard a while back that someone was getting 30+ on average. That might've been with the ECU though, which I've thought about doing, but I don't want to if I have to use premium gas.
Last summer for just a little while, I got 28-29 on average. I'm not sure why it dropped.
Also, when I was steam cleaning the engine bay this afternoon, I noticed an empty screw hole on the right side of the block (when viewed from the front). Any idea what that might be?

 

[MrsZR7]

Oh yeah, it's also a manual transmission.

 

[MrsZR7]

I also forgot to answer about driving habits.
I drive 44 miles round trip, 5 days a week for work. Most of that (I'd say...take 15 miles off that to get to and from the expressway) is on the expressway. Of course 55 is the "suggested" speed limit but I'm usually going about 70 on average. I don't race or drive it like I stole it, as a rule. Occasionally I'll play on a good country road, but there's not too many of those in my area.
Tire pressure is good. In fact, I've also got nitrogen in my tires, for what it's worth. This is the first time I've ever sprung for that, which I got when I picked up the car at the dealership.

 

[SoCalMP5]

I've been looking a lot into the basic differences between our P5's and the really miserly, high MPG cars. There's a few obvious reasons why the P5 isn't physically capable of the economy that some other small cars get.

Compared to ultra gas mileage cars, our P5 is several hundred pounds heavier, with an engine displacing 20-25% more, and the gearing in 5th is just too short...it's like an automatic without an overdrive and revs are too high for economy.

If someone was willing to gut their car and get it down to ~2350 or so, and install a taller 5th, then it would certainly bring the avg mpg way up. When I have the money I'll be doing a bit of ecomodding...my goals are 28 city and 33 highway. On paper, it seems like it shouldn't be too hard.

People who claim 32+ mpg with stock cars make me question their methods of calculation...because it seems pretty much mathematically and mechanically impossible without ecomodding.

 

[Teeson]

I do all highway driving, commuting. I've been keeping the revs around the 3k mark where our car's are supposed to be most efficient. I think I can safely say there is validity to it, as i just clocked 32 mpg. I also have an CAI, axle back, low resistance tires and a lead foot. I also shift at 3k every time, then in 5th keep it at 3. My round trip is approx. 80 km, I average about 600 km to a 50L tank (canada eh!).
Honestly I don't think these cars are as fuel efficient as they should be, I blame the crummy underpowered old ford engine mazda stuffed in there...

I also don't think that seafoaming every tank is neccessary.. Neither do I think that an MP3 ECU will help, you'll spend any money you save from mileage on premuim.

If I were you, I would do a drop in K&N and an axleback.. say racing beat, avoid the fart cans. A ECU reset later and I got some good MPG gains

 

[MrsZR7]

Teeson, what kind of CAI do you have? You described your driving habits as I would describe mine (except for maybe watching the RPMs as closely, but I do have a lead foot for sure)... So if you're getting good numbers, I should try some mods you've done.

I had a Ford Focus (biggest POS ever!!) before the P5, and I did put a CAI on it. The gains on performance were slight, but I don't recall any MPG increase.

 

[digitalslacker]

I've been looking a lot into the basic differences between our P5's and the really miserly, high MPG cars. There's a few obvious reasons why the P5 isn't physically capable of the economy that some other small cars get.

Compared to ultra gas mileage cars, our P5 is several hundred pounds heavier, with an engine displacing 20-25% more, and the gearing in 5th is just too short...it's like an automatic without an overdrive and revs are too high for economy.

If someone was willing to gut their car and get it down to ~2350 or so, and install a taller 5th, then it would certainly bring the avg mpg way up. When I have the money I'll be doing a bit of ecomodding...my goals are 28 city and 33 highway. On paper, it seems like it shouldn't be too hard.

People who claim 32+ mpg with stock cars make me question their methods of calculation...because it seems pretty much mathematically and mechanically impossible without ecomodding.

Honestly 32mpg is doable. I made a trip last fall from Lancaster PA up to Boston. Most of the trip was 55mph highway so I was cruising about 60. For the trip up I averaged 34mpg. I don't drive like a nut, I made sure I had my tire pressure up to the max suggested and recently had an oil change with synthetic. All mpg calculators were done with writing tank milage on the receipts and using fuelly. I understand there is some variance with how full different fuel pumps will make the car but they should be close enough not to throw it all that much off.

 

[SoCalMP5]

Honestly 32mpg is doable. I made a trip last fall from Lancaster PA up to Boston. Most of the trip was 55mph highway so I was cruising about 60. For the trip up I averaged 34mpg. I don't drive like a nut, I made sure I had my tire pressure up to the max suggested and recently had an oil change with synthetic. All mpg calculators were done with writing tank milage on the receipts and using fuelly. I understand there is some variance with how full different fuel pumps will make the car but they should be close enough not to throw it all that much off.

Sure, it's doable...with the variables you introduced. But your car isn't stock, and your speed was lower than most people drive...which is why your MPG was higher. A 100% bone stock '02 P5 driven at speeds closer to the flow of traffic (if you drive 55-60 around here, you're gonna get shot or rammed off the road, or maybe even get pulled over for suspicion of doing something else wrong - it's simply not realistic) will NOT be able to hit the numbers you did.

I want to do an exhaust for the MPG benefit, but (a) I don't want my car to sound like all the Hondas do around here, and (b) cops pull over cars that look like they might have something under the hood, so having a japanese car that looks sporty and has an aftermarket exhaust gets you unwanted attention by law enforcement.

Do you have any videos that show the exhaust note? I'm curious about it. But I'm sure ANY aftermarket exhaust will be too loud or too "ricky racer" for my taste. =\

 

[i12drivemyMP5]

Mine pulls 31 mpg dependably with sportauto driving it between 65-70mph, keeping it around 3k rpm on the freeway. Can't expect much more than that out of a 10yr old 90k miles 4cyl automatic running the AC. I do have int/hdr/full exh, all lightened pulleys, UDP, 1.8 coils, long reach zfr plugs, syn eng oil, syn atf with cooler, etc etc etc so it isn't exactly stock. I also have an FSZE intake manifold, MPI NA tuner, flying miata voltage clamp, innovate wbo2 with gauge & OBX hdr with 3 bungs that I haven't got around to installing yet. That should yield a tiny bit more power and less wasted fuel due to the pig rich oem tune. Not sure how much more mpg it'll give me but eventually I'll be finding out. Should free up a couple more mpg I would think. Getting around 390-410 a tank now and usually filling back up with 12.5 - 13.5 gallons on avg. Topography = mostly flat, 0 - 150 ft above sea level. Pretty much all frwy driving, about 80%, maybe 5 or 6 miles of my 30 mile commute is city driving.

 

[digitalslacker]

Sure, it's doable...with the variables you introduced. But your car isn't stock, and your speed was lower than most people drive...which is why your MPG was higher. A 100% bone stock '02 P5 driven at speeds closer to the flow of traffic (if you drive 55-60 around here, you're gonna get shot or rammed off the road, or maybe even get pulled over for suspicion of doing something else wrong - it's simply not realistic) will NOT be able to hit the numbers you did.

Wait, so because I drove 5mph over the posted speed limit and not 80mph my experiences are not normal? Right.

Bottom line is mpg is all how you drive it.

 

[i12drivemyMP5]

Yep, if I drive mine 75-80 it'll burn a very small amt of oil ( less than 1/8 qt a month) and the mpg will drop down to 24-25 mpg. As long as I do normal 3000-3500 rpm shifts in manual mode or just drive normal in auto mode and stay between 65-70 for the most part, it will do 30-31 mpg and not burn any oil.