Bad gas mileage

[Dave_x]

I've found that disconnecting the battery gives me a crappy next tank while the computer figures things out again.

Something might be up. I just had a 400 mile tank with a good mix of city/hwy driving and I've done nothing special to my car. Slowing down has bumped my mileage a good 20-30 miles a tank though.

 

[maxchao]

Damn guys, I bought this car for good MPG and its terrible. How can such a low horsepower 4-cylinder on a fairly light car get such bad gas mileage?

We aint honda lol...

 

[Kymerik]

...I haven't got less than 33mpg since i bought the car in february outside of my first 2 tanks i got mid 20s...

I switched to a lightweight synthetic Transmission fuel (mixed with Syncromesh) and lightweight synthetic motor oil. Oh and i run 48PSI in my tires (max is 51)

You're either pushing it harder than you think OR theres a problem with your car

 

[erzipper]

Trust me, I am not driving it hard at all. Having three Hondas before this I'm starting to see why Honda has better reputation than Mazda. My Prelude with an H22 (195 HP, 156 ft/lb) consistently averaged 29 mpg tanks and I drove it HARD. Something must be wrong...

 

[maxchao]

48 psi seem to be too high i think...

Josh

 

[pr5owner]

48 psi seem to be too high i think...

Josh

48 is way too high, once you hit a bump hard the pressure goes past 51 and you get bulges on your tire then they eventually just blow out

 

[pr5owner]

Trust me, I am not driving it hard at all. Having three Hondas before this I'm starting to see why Honda has better reputation than Mazda. My Prelude with an H22 (195 HP, 156 ft/lb) consistently averaged 29 mpg tanks and I drove it HARD. Something must be wrong...

honda is just better than mazda, honda's vtech lets you have good power past 4K RPM and good gas millage anywhere under. all cars should have 2 cam profiles.

however, preludes cost $32K canadian new (at the time in 2001), a protege5 costs $20600 (for me anyways with tax in, frieght, everything)

 

[winston3x]

nobody ever mentions geography. Seems like the 30+ mpgs are always in places with no hills.
what's the topography like where you are erzipper?

 

[erzipper]

Pretty flat man.

 

[winston3x]

i usually get 24-25 in town. That's auto, all city, short trips, every street has some % grade. I do have new plugs/wires/coils/fuel pump & filter/ air filter.
if yours goes back up to 26, I don't think that would out of line for these cars.
I do get 30 on all interstate trips.

you could probably chalk the sub-30mpg to the torque converter,ethanol blend and A/C (if you're using it).

 

[pureliquidhw]

fuel type plays a huge role in MPG. My 95 pro got 38mpg on a recent trip. In the winter, i'd be lucky to get 30. My p5 gets 28-29mpg on the interstate regardless of speed. But you're right erzipper, the power/economy tradeoff isn't there, but as someone else has said on these forums "it's a zoom zoom thing, you wouldn't understand."

 

[Donas64]

I have hills all over the place. Heck Lynchburg is the Hill City!

 

[maxchao]

Oh that's right, I just realize I'm in hilly Georgia and all the gas I get has 10% ethanol in them. Plus my driving, all city, and summer tire maybe 22mpg makes sense.

Josh

 

[i12drivemyMP5]

Everyone should just take obama's "advice" & make sure your tires are filled up & get a tune up. They act like that alone should solve the gas crisis. What thin weak nonsense.

 

[Donas64]

Everyone should just take obama's "advice" & make sure your tires are filled up & get a tune up. They act like that alone should solve the gas crisis. What thin weak nonsense.

Yeah, I laughed when I heard him say that. I knew that was my problem all along. under inflated tires and a crappy tune! Good grief.

I've just learned to pretend like my P5 is a Mustang GT then my mileage doesn't seem so bad.

 

[pasadena_commut]

We have been over most of this ground before, a lot of the variation is just slop in how we characterize the "average drive". See for instance:

http://www.msprotege.com/forum/showthread.php?t=123636065

The biggest real difference between P5's is auto vs. manual in the city, where "normal driving" in the former tends to get 21-22 and in the latter around 25. Blame it mostly on the torque converter. On the highway they are both in the 30-32 MPG range. The top gear is too low in the P5 for best efficiency, my auto does about 3050 RPM at 70 MPH, the wife's Subie wagon is hundreds of RPM lower at the same speed.

I have been able to increase my city fuel efficiency to an average closer to 24-26 mpg by changing driving habits and routes. To get the better results it is necessary to take a route with lights which may be timed (to avoid starts and stops). Now I find myself hanging back enough so that traffic ahead can trigger the lights, and I'm typically coasting towards red lights, foot off the gas, in order to conserve kinetic energy. I think disk brakes drag a little after they are applied and released, so not applying them in the first place also eliminates that energy loss. Of course I use them when I have to.

Tires can make a difference, but it is practically impossible to find the actual rolling resistance numbers. so it is very hard to factor this in when buying new ones. The best you can do is keep them inflated. My tires are at 33 PSI all around - I tried higher, which would reduce rolling resistance some, but the ride was like dragging my butt on a shovel down the road.

 

[Magus]

I think the gearing, fuel tune, and compression are what is killing MPG around town. I get around 25 mpg around town, but I have a couple mods that help:

Injen styled CAI w/ AEM bypass
SLS front motor mount
UR UDP (crank pulley) from Protege Garage
R1 Slotted/drilled rotors
205/50-16 BF Goodrich Traction T/A v-rated @ 36 psi

If I drive hwy speed plays a big mpg part. 31 mpg @ 70mph/60mph
33-34 mpg @ 65mph/55mph

I would point at this is not hilly terrain going from Elkton, MD to Baltimore.

If I want further mpg, I would do Aero tuning and exhaust work. The only way to get better mpg around town might be fuel tuning.

 

[pasadena_commut]

If I want further mpg, I would do Aero tuning and exhaust work. The only way to get better mpg around town might be fuel tuning.

The simplest aero mod for the P5 is to take the rack off. At highway speeds racks usually drop fuel efficiency by 1 to 2 MPG. Also check underneath that none of the plastic shields is broken, hanging down, and acting like an air brake. If one broken it does not necessarily need to be replaced, they can usually be duct taped back into a serviceable shape, bigger holes can be patched with vinyl floor squares (up to a point).

I'm not sure fuel tuning would be all that much help around town, at least for the automatic. In any case, wouldn't it require a different or additional ECU, and wouldn't that likely cost more than you would ever recover in fuel savings? I just wish the torque converter would lock in 3rd. Sadly it will only lock in 4th gear above 35 mph (roughly). In city driving it is rarely locked, so at least 10% of that expensive gas is wasted churning and heating transmission fluid.