Bad mpg?

BIG ROLLER

BIG ROLLER

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Right now I am getting 16 mpg with a mix of both freeway and city. I just did a tune up for the first time (plugs, wires, air filter and fuel filter) since I have owned the M8 last month and now I am going to get my O2 sensors replaced.

Car is all stock.

Next will be the MAF sensor.

Got new tires all around.

What else should I look into?

Vacuum leak?

EGR?

And????????

What should I expect to pay for O2 sensors at a shop? Can't get to the sensors myself.

I can also use a control panel. If anyone has a grey panel PM me.

I also need a front spoiler but I think I found one local. Just have to stop at the house and ask.
 
Why replace MAF? If there's not a code for it, just give it a blast of MAF cleaner

Also keep in mind that the MPG is an average .. so if that 16mpg display had calculated several sits at a stop light.. then I'd say do a reset on the freeway and get a more accurate display for extended constant driving

You'll be looking at a $300-$400 bill for parts and labor to have the O2s swapped
 
Good point with the MAF.

The reset button doesn't work. I haven't driven far on the freeway much lately so I haven't calculated what much of a difference that might be.
 
why so much on 02 are they that hard to change on this car. and hell after i got my 4.10 gears and a tune im lucky if i get 13.8 mpg
 
your dash display center should also tell you instant mpg, I use that to keep my foot off the floor and race less;....get on the highway, cruise on a long flat stretch at 65 mph, check instant mpg to find out what you're getting, I get about 32 under those circumstances
..last week I worked about 12 days in a row and drove the car almost exclusively on the highway, with very few traffic jams; after i filled up i calculated I got 25.5 mpg; the cars computer said 23 average on that full tank
 
My MPG was low and it was tire pressure. Technically they are overfilled a bit now, but MPG is back up to 27 on the highway.
 
get your foot off the loud pedal. :D

a little low, but not absurdly, i averaged about 18 when stock combined hiway/city.
 
BIG ROLLER said:
Good point with the MAF.

The reset button doesn't work. I haven't driven far on the freeway much lately so I haven't calculated what much of a difference that might be.
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If your driving hasn't been so much on the freeway, I'd say it sounds about right.
Mine gets 27-30 on the freeway with the cruise set to 80mph.
 
mileage drop

I think it's the crap they put in gas during cold weather. My 95 dropped from avg combo mileage from 19.5 to 15.3 with a fresh tune up. My 98 17.5 to 16.1(dont drive it too much) My PU 12.7 to 11.5. Have to figure in more warm up time. I did do the intake mod on the 95,but I dont see how that would hurt mileage. They all get a shot of sea foam at fill up. I'm putting the blame on CRAP IN THE GAS and waiting for warm weather gas to see if it makes a difference. :D
 
It's all about the ethanol. The more ethanol, the decrease in fuel mileage. One other thing, if your vehicle sits for a long time, put some ethanol treatment in the gas. You don't want the ethanol to separate from the gas. The leftover gas is a lower octane
 
Sapperfire said:
You'll be looking at a $300-$400 bill for parts and labor to have the O2s swapped
Click to expand...
That is what I expected.

sprocket said:
My MPG was low and it was tire pressure. Technically they are overfilled a bit now, but MPG is back up to 27 on the highway.
Click to expand...
They are new tires but I should still check the pressure. Right now I am only driving the car only about 4-5 times a month lately.

chris2523 said:
get your foot off the loud pedal. :D

a little low, but not absurdly, i averaged about 18 when stock combined hiway/city.
Click to expand...
So I'm not too bad than. It's that time for maintance and I want to get the mpg as close to stock as possible for now.

Psychostang said:
It's all about the ethanol. The more ethanol, the decrease in fuel mileage. One other thing, if your vehicle sits for a long time, put some ethanol treatment in the gas. You don't want the ethanol to separate from the gas. The leftover gas is a lower octane
Click to expand...
Didn't think about using ethanol treatment. The M8 could use it that is for sure.
 
Ok

Took the 95 for a 80 mile drive (casino run) On CC at 73mph avg car said 18.9 with pencil avg 19.0 I'm happy now,and casino pts paid for gas. :D:D
 
If the O2s are still the stock ones, change them and you should get into the 20s
Depending on the miles you may want to start thinking about the exhaust system

How well the last owner took care of it will be a factor until you either replace or clean out parts
Run some seafoam thru the tank, brake booster vac hose and a little in the oil will help clean out a lot of the gunk in the engine and injectors
 
Solved my mileage problem on a chance remark I read here. I have a stand alone tranny cooling set up and in the winter it is too cold for the torque converter to ever enter lockup. Apparently it needs to reach a minimum temperature for the computer to allow lockup.

A piece of cardboard will do for now.
 
PenGun said:
Solved my mileage problem on a chance remark I read here. I have a stand alone tranny cooling set up and in the winter it is too cold for the torque converter to ever enter lockup. Apparently it needs to reach a minimum temperature for the computer to allow lockup.

A piece of cardboard will do for now.
Click to expand...

What size tranny cooler? The 40,000#gvw cooler I run has a thermal bypass that comes with it. Unfortunately, I think that I chucked it because I never drive my car in the winter otherwise I would've sent it to you for free. :( That's what you really need and I bet you could find one for cheap.
 
Consider yourself lucky. In Miami, City/Hwy combined is 13 - 14mpg. City only is 8mpg. I'm getting 28mpg hwy now because I'm on a road trip but it all comes to what type of city you live in & the type of driving you have to do.
 
Driving style plays a huge part in MPG. Getting up to speed gradually and pacing traffic to stay off the brake pedal make a big difference. I know it depends on the city and some are stop and go no matter what, but it's amazing how many driver's gun the gas and then come quickly up on the car in front of them and hit the brakes. Over, and over. Not only is it hard on MPH, it wears out the brake pads and rotors.
 
O2's

The o2's were changed 2 months ago,new plugs,wires. Cleaned K&n filter,also intake mod. 1/2 tank of gas was combo, then 80 mile highway trip. End result not bad. Wifes DD and she has heavy foot but brakes at last minute. I add a shot of sea foam to tank at fill up,but have'nt done the intake method, neighbors have'nt ticked me off enough. I've had the 95 for 14 years and maintence is done more than needed. Just switched to Mobil syn oil. In the spring it gets a new set of Michlen primacy's and like new 10 spoke chrome wheels. This should get the milage up a bit.I do check the air pressure on all the vechiles once a month. Before my 1st Lincoln MKVIII I had a 74 T-BRD for 21 years,no milage there. :D
 
I agree it depends on where u live mainly due to the high volume of stop and go and traffic around me here in Atlanta i only average about 16 mpg on the average with both but with the instant it stays roughly in the mid 20s on 45 mph stretches.
Changing all of my O2 sensors soon too. Keep getting that damn CEL and with it say 2 different banks I'm just going to change all 4 and b done with it. Should increase a great deal. But i dont really drive mine much a full tank usually lasts about a week and a half or alittle more since everything is close by. And that has a big effect also how far u drive.
 
Mine is usually in the 15's and 16's in the city but that includes setting at stop lights and letting it set and warm up before I pull out of the garage.If I hit reset on the HWY, I'm seeing 25 to 26, sometimes 27 and I run 93 and use 764 copper plugs (for now). I got some new Autolite Iridium XP104's that I haven't put in yet. I also use the black bottle of STP fuel injector cleaner about every 2 or 3 tanks and Mobile 1 fully synthetic oil. Car idles at a stop light extremely smooth, to the point of not even feeling it, almost. Maybe the plug change will raise the mpg's up a little but I don't think 16's is that bad, especially if your reset button isn't working. I'm surprised it isn't showing 14's or less, if a lot of city driving is being done.
 
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