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I have owned 2 mx-6's and 2 626's, all 1st gen, all with relatively the same gas mileage. I recently bought a sweet mx-6 GT and did a rebuild. I finally got everything put back and I am driving the car regularly now. I love the way the GT handles on the highway...just press on the pedal and the turbo brings you up to speed. Anyway, I travel about 120 miles a week and I am only getting about 20mpg, which sucks for these cars. I want to know if anyone has any tips to getting the gas milage to where it should be.
 

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That's pretty crappy. I did a tune-up, cleaned my fuel injectors, performance air filter, etc. Pretty much anything you do to increase the cars efficiency the better the gas mileage you'll get.

I get about 28mpg with my lead foot. Half city & half highway.
 

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have you checked or replaced:

air filter
Pcv valve
Fuel filter
Spark plugs/wires
Exhaust leaks
Freely spinning turbo (impeller not hitting housing)
Wheel bearings
Age of injectors? Leaky injector o-rings...etc..
Probably some other stuff I can think of.. just not right now..


I get 29-34mpg, and Drive like a grandma, and have a nasty exhaust leak, that will be fixed tuesday. :)
 
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Getting really bad gas mileage

forgot to mention that i was smelling gas fumes coming from the rear drivers side, and i could not figure out where they were coming from. i thought that maybe the a return hose from the tank was broken. turns out the fuel cap is not sealing correctly...you think this could have contributed to my bad mileage? btw...when i did the rebuild i replaced the...

air filter
Pcv valve
Spark plugs/wires

However, i did not replace the fuel filter...how would this affect the gas mileage?

don't have Exhaust leaks, replaced all gaskets when i got the rebuild kit.

wheel bearings...wheels spin freely, no screaching, plenty of grease!

Freely spinning turbo (impeller not hitting housing)
now this one i don't have a clue on...please elaborate if you can, thanks. and as far as i am concearned the turbo is doing it's job, he,he, he

Age of injectors? Leaky injector o-rings-
injectors are original, as far as i know they are working they way they are supposed to, i have not measured them...i saw a 1990 gt h/b at a u-pick yard with only 85k on it...was thinking of taking the injectors off that!

AT THIS POINT I AM JEALOUS turbogt22 !

I OWN A 1990 626 THAT IS GETTING 37MPG ON THE HIGHWAY...YOU GUESSED IT...I DRIVE THIS ONE DURING THE WEEK, AND DRIVE THE GAS GUZZLER ON THE WEEKEND!


Freely spinning turbo (impeller not hitting housing) Age of injectors? Leaky injector o-rings :D wheel bearings
 

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Basically, if the turbo isn't smoking under idle, and it doesn't sound like a siren when boosting (that's the impeller hitting the housing because of excess shaft play or oil starvation) then you're ok....

The fuel filter, if it's somewhat blocked it's hurting your mileage..... they are about $20 USD and take about 5 min to replace. I'd replace it (you're "supposed to" every 15k miles or 30k miles I forget which)..... I'm kinda anal about that stuff, I replace the plugs every 3 oil changes, and the fuel filter every 5 oil changed... It's cheap insurance for better gas milage...

Also, it's probably your injector o-rings leaking.... I believe there's either 2 or 3 rings per injector, and the "injector o ring kit" is like $2.19 (times 4) and it's a VERY easy DIY replaement. These will get hard and plasticy just like any other rubber part, if not sooner because they are exposed to an extreme amount of heat, then cold, then heat, then cold.... you get the pict... expand, contract, expand, crack, leak.... ECU makes car run rich to compensate for the fuel loss... Trust me, it's worth it to replace them... It may be a fuel line cracked somewhere.... grab a screwdriver and go around and tighten all the hoses and see if it helps.
 

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yeah i know the feeling i'm actually getting pretty bad mileage too, around 19mpg, i used to get alot more at least 25 and not much has changed,

changed fuel filter have K&N drop in filter, pcv valve good, changed to iridium plugs, new cables distrib cap and rotor... i'll try pulling out and cleaning those injectors some.

Any other stuff thats more technical say egr valve... thermostat... can bad hla cause this problem? thx all
 

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sadly i think i get the worst gas milage here, i average about 15 mpg lately, and thats when im not beating on it, the best ive ever seen it is at like 18 mpg, i hate having the trip computer that tells my my gas milage. its very depressing.
 

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do you do a lot of city driving? That hurts mileage too. A/C on? yup, down goes the MPG...

Do you have mods that are making your car run rich? That hurts the mileage as well.....

Mine may seem so high because about 90-95% of my driving is hiway mileage...A/C off, and the only mod I have is an intake. (I fixed the hole in my exhaust today with a new pipe, so we'll see how that goes).....

your 02 sensor may be a factor as well... I think they are like $30-$40 for these cars, that couldn't hury by replacing that.
 

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i know how you all feel, i was getting around 15 - 17/g. couldn't drive across town without spending a few bucks at least...
but - now i get about 30...

try these, helped me out big time :

- use some injector cleaner in one full tank, that always helps...

- in the next (make sure this is a fill-up), throw in carb and valve cleaner (7-11 sells it for 1.99, cheap stuff - and not having a carb doesn't matter, its basically octane and detergent anyway)

- use premium as much as possible - may cost a bit more, but trust me you're saving her from certain death.

- next time you do an oil change, throw in castrol high mileage if you're over about 120,000 km. It'll help fill in any scratches in the cylinders, which should help with fuel consumption AND compression, an added bonus.

- also double check the connection from the distributor to the air flow meter... krazy glue is a good temp fix for that one, rather than replacing the whole case... (speaking from experience. but do read the warning labels... they mean it ;) )

- gas smell was most likely coming from the gas cap, but if shes misifiring at all sometimes you can smell gas fumes in the exhaust... best way to check for that is to start it up on a hot day, let her warm up, and watch the exhaust - if it looks steamy like your early morning cold start, chances are you're not burning all your fuel, which would be the plugs misfiring or injectors... listen for the give-away-tick. if your car sounds like my watch, and you're using a lot of gas, its the injectors.

- check and make sure you dont have oil on the rear of the pan... that isnt the pan leaking, i believe its the return line above it - but it can drip pretty good at high pressure - more friction, more power needed for same work, more fuel needed for power.

- and if you're still getting bad mileage, check the newbie stuff first - tire inflation, oil, spark plugs, etc.

- if that doesn't help, then your 6 is more tempermental than mine - which is definately not the best thing... LOL

best of luck, and buy me something nice with the $ you save if it works ;) ;)
 

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poor mpg

Make certain that the motor is in a good state of tune. Check all of the basics, pull the codes, try a different brand of gas, control your driving style and conditions. The O2 sensor, timing, egr and other emission devices must be functioning properly for optimum fuel economy.
But sadly, an older car such as the "6"s, which have been somewhat neglected and driven hard are not going to get great mileage as when new.
 

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i do about 80% highway driving, and always with the AC off, so it's not that. Scary thing though, i have been seeing oil on the back of my oil pan... and my right control arm is pretty much soaked in oil.... i know this cuz i washed my engine and it was spotless, now the entire right side is all oily.

BTW wouldn;t poor oil circulation cause more problems then just bad mileage by now?

thanks for bringing this up, i really want to check out that oil return line now. where is that oil return line and what do i need to do?
 
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el norm said:
i do about 80% highway driving, and always with the AC off, so it's not that. Scary thing though, i have been seeing oil on the back of my oil pan... and my right control arm is pretty much soaked in oil.... i know this cuz i washed my engine and it was spotless, now the entire right side is all oily.

BTW wouldn;t poor oil circulation cause more problems then just bad mileage by now?

thanks for bringing this up, i really want to check out that oil return line now. where is that oil return line and what do i need to do?
The oil return is on the front of the block. It sounds to me more like a leaking crank seal.
 
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emexix said:
i know how you all feel, i was getting around 15 - 17/g. couldn't drive across town without spending a few bucks at least...
but - now i get about 30...

try these, helped me out big time :

- use some injector cleaner in one full tank, that always helps...

- in the next (make sure this is a fill-up), throw in carb and valve cleaner (7-11 sells it for 1.99, cheap stuff - and not having a carb doesn't matter, its basically octane and detergent anyway)

- use premium as much as possible - may cost a bit more, but trust me you're saving her from certain death.

- next time you do an oil change, throw in castrol high mileage if you're over about 120,000 km. It'll help fill in any scratches in the cylinders, which should help with fuel consumption AND compression, an added bonus.

- also double check the connection from the distributor to the air flow meter... krazy glue is a good temp fix for that one, rather than replacing the whole case... (speaking from experience. but do read the warning labels... they mean it ;) )

- gas smell was most likely coming from the gas cap, but if shes misifiring at all sometimes you can smell gas fumes in the exhaust... best way to check for that is to start it up on a hot day, let her warm up, and watch the exhaust - if it looks steamy like your early morning cold start, chances are you're not burning all your fuel, which would be the plugs misfiring or injectors... listen for the give-away-tick. if your car sounds like my watch, and you're using a lot of gas, its the injectors.

- check and make sure you dont have oil on the rear of the pan... that isnt the pan leaking, i believe its the return line above it - but it can drip pretty good at high pressure - more friction, more power needed for same work, more fuel needed for power.

- and if you're still getting bad mileage, check the newbie stuff first - tire inflation, oil, spark plugs, etc.

- if that doesn't help, then your 6 is more tempermental than mine - which is definately not the best thing... LOL

best of luck, and buy me something nice with the $ you save if it works ;) ;)

thanks for the tips. believe it or not i replaced the gas cap on my gt with one from my 626 and my gas mileage has gone up!!!!!!!!!!!!!!! as you can tell from the the exclamation marks, i am confused but extremely happy. it shot up from 20mpg to 30mpg. the smell of gas fumes has somewhat dissipated. the next thing i am going to check is the injectors. my plugs are fine,(brand new, gapped to spec.). and the wires are brand new. i am going to replace the fuel filter when i do the injectors, who knows when that thing was even looked at.

but i mean really have you heard of such a thing as replacing a gas cap to get better mileage? i swear to god that this is all i did! and now i am getting reasonable mileage....my old gas cap had a hole in the middle of it, which explains the fumes i was smelling.
 

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do the injector cleaner bout 1 a month, allways use mobil 1 oil, allways use mobil premium gas, new plugs, wires, fuel filter, o2 sensor, have the egr removed, but even when i had it, gas milage still sucked. a/c doesnt work, so its never on, and i pretty much just drive in town,
any other ideas to get my gas milage to at least 20mpg?
 
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Discussion Starter #15
emexix said:

- use premium as much as possible - may cost a bit more, but trust me you're saving her from certain death.
Nope, Premium fuel = Higher Octane = Burns slower = More gas passed through unburnt. Waste of money unless your running higher than stock boost.


- next time you do an oil change, throw in castrol high mileage if you're over about 120,000 km. It'll help fill in any scratches in the cylinders, which should help with fuel consumption AND compression, an added bonus.


Does nothing for the cylinder walls, instead it soaks into the rings and valve seals and helps them seal better.


- also double check the connection from the distributor to the air flow meter... krazy glue is a good temp fix for that one, rather than replacing the whole case... (speaking from experience. but do read the warning labels... they mean it ;) )
There is no connection directly from the VAF to the distributor...Did you mean coil?


- gas smell was most likely coming from the gas cap, but if shes misifiring at all sometimes you can smell gas fumes in the exhaust... best way to check for that is to start it up on a hot day, let her warm up, and watch the exhaust - if it looks steamy like your early morning cold start, chances are you're not burning all your fuel, which would be the plugs misfiring or injectors... listen for the give-away-tick. if your car sounds like my watch, and you're using a lot of gas, its the injectors.


Unburnt gas is emmited as a dark black smoke, not as a misty white smoke. White smoke is either condensation in the exhaust or burning coolant.


- check and make sure you dont have oil on the rear of the pan... that isnt the pan leaking, i believe its the return line above it - but it can drip pretty good at high pressure - more friction, more power needed for same work, more fuel needed for power.


There is also the rear crank seal up there, and the oil pressure switch. The latter being very prone to start leaking at high milage.
 

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gas tank filler cap

evrynite-TURBO said:
thanks for the tips. believe it or not i replaced the gas cap on my gt with one from my 626 and my gas mileage has gone up!!!!!!!!!!!!!!! as you can tell from the the exclamation marks, i am confused but extremely happy. it shot up from 20mpg to 30mpg. the smell of gas fumes has somewhat dissipated.

but i mean really have you heard of such a thing as replacing a gas cap to get better mileage? i swear to god that this is all i did! and now i am getting reasonable mileage....my old gas cap had a hole in the middle of it, which explains the fumes i was smelling.

Gas cap= 10 additional mpg !
Rather difficult to imagine, but I'm going to go out and buy a new one. That "hole" in the cap must've been doing some power-venting. Fortunately no one was smoking while near your "6".
 

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i got bad gas mileage too, I filled my tank and put the thingy on zero and when my gas ran it it said 2215km.. how much is that in mpg ?
 

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FlySwat said:
Nope, Premium fuel = Higher Octane = Burns slower = More gas passed through unburnt. Waste of money unless your running higher than stock boost.
High octane fuel is recommended for our turbocharged cars. You CAN but shouldn't be using regular...even if you're running stock boost.
 
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Discussion Starter #20
With a properly functioning knock sensor, your timing will be retarded with the slightest engine knock, therefore keeping the engine in good running order, albeit possibly slower, but we are discussing gas mileage not performance here. There is no way to get a stock motor to knock on 87 octane gas.

On the other side of the coin, the knock sensor cannot detect a higher octane gas, so it will not advance the timing until knock, would be nice, but it doesn't.

Running higher than 87 is a waste of money unless your running higher boost, have a chip, or have advanced your ignition timing.
 
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