MPG in my LX

[Alastor]

so since ive gotten my 94 mazda protege lx automatic, i have not gotten very great mpg, any tweaks i can do to get alittle more? i know factory these only get about 26 hwy but any way i could get that to 30? ive replaced the plugs, the fuel filter and it has a short ram intake on it, the car has a ton of miles on it so im thinking maybe i need to replace the fuel injectors and O2 sensor?


what is every one else getting?

[Kitty]

I don't think you'll get 30 highway with an auto-tragic.

The O2 sensor would help some.

I currently get 23-27 mixed EPA(which I feel was more accurate than current standards) for the car was 26 mixed IIRC.
I have the Window sticker in one of my bins.

[Alastor]

ah darn, well i guess i'll get a new O2 sensor and see if it helps some what, i feel like the injectors being replaced would help abit aswell, im sure after 263k miles there tired

[ThatGreenBG]

I barely break 32mpg on the highway (rated at 28) with a full exhaust and the stock intake with my manual LX. Doubt you'll do much better than you are with the auto, unfortunately.

[JNKW]

Put the stock intake back on. Not sucking hot engine bay air will help.

[ThatGreenBG]

Put the stock intake back on. Not sucking hot engine bay air will help.

Actually, hotter air is said to be better for fuel economy.

[me109]

I only got about 28 mixed in my last LX. The other one was fantastic. It gave me consistent 32s mixed (avg/tank) and once spiked to 35.4! I think the fuel was better in those days.

[Kitty]

Ethanol confirmed a ****.

[Alastor]

i changed the PCV valve, o2 sensor, and plugs/wires and a new cone filter and now its much better, i drove it about 70miles yesterday and the gas hand barely moved, came out to about 27mpg avg at 65mph on the highway, so im pretty happy now,

[1LordAnubis]

Increase your tire pressure; I've found 40 psi to work well; the 32 psi recommendation on the door is extremely low, tires are usually rated 44 psi, and i've found @ 32 they seem to wear more on the outside than i'd like
There's not really much more you can do with an automatic.... a manual would be more efficient, plus you could put it into neutral & coast to save even more fuel.

My 93 protege DX 5 speed got about 30 mpg when i first got it, changed the plugs and it went up to 32 mpg; today I get 33 mpg on the highway, 36 if I'm trying to conserve fuel. Interstate driving varies; but even if i have the pedal to the floor @ 4500 rpm for a long period of time I still get 27 mpg... but thats with a ton of abuse. The best I ever got was driving in the mountains... 38 mpg
When I log on later I'll post my gas log for last year, just for reference... though alot of it is inefficient interstate driving... I mean, there just isn't much torque in 5th gear & it takes fuel to maintain high rpms

[Alastor]

Increase your tire pressure; I've found 40 psi to work well; the 32 psi recommendation on the door is extremely low, tires are usually rated 44 psi, and i've found @ 32 they seem to wear more on the outside than i'd like
There's not really much more you can do with an automatic.... a manual would be more efficient, plus you could put it into neutral & coast to save even more fuel.

My 93 protege DX 5 speed got about 30 mpg when i first got it, changed the plugs and it went up to 32 mpg; today I get 33 mpg on the highway, 36 if I'm trying to conserve fuel. Interstate driving varies; but even if i have the pedal to the floor @ 4500 rpm for a long period of time I still get 27 mpg... but thats with a ton of abuse. The best I ever got was driving in the mountains... 38 mpg
When I log on later I'll post my gas log for last year, just for reference... though alot of it is inefficient interstate driving... I mean, there just isn't much torque in 5th gear & it takes fuel to maintain high rpms

oh man thank you id like to see the log just to get an idea, its looking like it might be worth it to just say the heck with it and convert it to 5speed, which id rather have any way. hate automatics, but thank you for the tire pressure info aswell

[me109]

you could put it into neutral & coast to save even more fuel.

I have to disagree with this one point.

Since I installed my wideband I have confirmed that no fuel is injected on overrun as long as the engine speed is greater than 2000 r/min. This is far more efficient than coasting in neutral where idle must be maintained. You're better off engine braking a little bit.

I agree with the rest though. Especially the bit about the tire pressure. 40 works well for me.

[Kitty]

Popular mechanic agrees on that

http://www.popularmechanics.com/cars/alternative-fuel/news/coasting-in-neutral-fuel-economy

Being in neutral also makes cars handle weird to me. Weight balance or something, never bothered to figure it out.

[1LordAnubis]

When I got the car:
Alright, this is last year's log:
Alot of this is interstate driving, most frequently ~80 mph & city driving... about 50/50. @ 8/24 I tried to save gas by driving on the slower highway, & pumped the tires up to 36 psi. I tried coasting to save fuel & got ~36. 9/29 was a trip on the interstate, and the 38 mpg on the next one was simply mountain driving. There's a big space in nov since i had to replace the wheel bearings, replace the struts, new tires, etc. and I swear these michelins give me worse gas mileage.

This year's log: excuse the huge gap... fragmented receipts, and lots of redoing stuff on the car, plus I ended up boycotting a local shell station after some bad experiences with the pumps not cutting off on two occasions, meaning I had no accurate recording for the gas log...

I have to disagree with this one point.

Since I installed my wideband I have confirmed that no fuel is injected on overrun as long as the engine speed is greater than 2000 r/min. This is far more efficient than coasting in neutral where idle must be maintained. You're better off engine braking a little bit.

I agree with the rest though. Especially the bit about the tire pressure. 40 works well for me.

Darn, I would have expected something a little more in depth from popular mechanics...
Well, it depends on the type of driving, and the rpm/speed, i suppose. Every time I try coasting/going back into gear i get ~36 mpg like clockwork, otherwise ~33 mpg, all other conditions basically equal.
However, keep in mind that I live on flat land. *Not* going downhill, it this case it would be more efficient to keep the car in gear.
When you have the car in gear, and have your foot on the gas to maintain your highway speed, you are using gas. If you let off the gas, you are running on vacuum with no fuel being used in the engine. However, when you do this at highway speed on these vehicles it's like hitting the brakes... you lose quite a bit of momentum, enough in fact that for me, on flat land ~35-65 mph, less total gas/mile is used coasting. When you are coasting with the car on, fuel is being used to maintain the engine speed. However, I've found this amount of fuel to be less than the amount required to overcome the engine. Coasting = minimum amt of fuel, but no loss of momentum from engine ... Letting off gas in gear = no fuel, but bam, that engine brake is on, and you need *more* fuel to overcome it up on acceleration.
I dunno, perhaps it's just easier to 'drive like you have no brakes' coasting?

That being said, the highest gas mileage I've achieved was with the car In gear, not coasting, in the mountains @ 38 mpg. Going up the mountain was in 3rd gear, pretty high rpm, but going down.... all the way.. in gear thus using no gas, pretty much the perfect system.

I don't really recommend coasting, however.... unless you really need to conserve fuel, and if so I'd only try it in a semi controlled environment; i.e. at night when there aren't other ppl on the road, and on a highway you are familiar with. I've found coasting not to be worth it... you have to hit the clutch quite a bit, I'm sure it probably wears on the throwout bearing, if you match the rpm to what it should be for your mph/wheel speed, then there shouldn't be any clutch wear, but if you spend all that time idling coasting down the road, it'll probably wear/burn your valves as they need the higher rpm to remove heat from them.

I would like to conduct further testing to 'prove' under controlled driving conditions the fuel consumption-engine braking momentum argument

One other thing that will conserve gas, however, is removing the AC compressor; just take the belt off, take out the ~4 bolts? on the compressor, chuck it, and put on a smaller belt to go just to the power steering and bam, +~2-3 mpg (in my case)

[Alastor]

oh wow thank you for posting that info, also which michelin tires? i was planning to put of a set of michelins on my car but if you have gotten bad mpg from them im not going too.