Poor gas mileage?

[Raudermaster]

Yea yea I know it's a HiPo V8 then why'd I buy one. No but seriously though, when I first bought the car, I could get almost 300 MPT bone stock. Once I did the intake/mufflers/tune it only dropped to about 280, 250 lowest. Then, once winter hit, it seems like it went to hell. I figure'd dirty air filter, never cleaned it though throughout winter. I cleaned it this past weekend along with cleaning my engine bay, and it's pretty much the same. What the hell else could it be that is still causing me to get bad gas mileage?

[sailsmen]

MPT is an inaccurate way to measure.

Try MPG and then report back.

[RCSignals]

Do they use a "special" winter gas blend where you are?

[fastblackmerc]

Try keeping your foot off the go pedal. My wife can get 21 - 22mpg when she drives, I'm lucky to get 17 or 18mpg :eek:

Cause I use the go pedal as an on / off switch.....

Either it's on or it's off....... :lol:


I didn't get my MM for the gas mileage.

[sabtaj1]

I only get 220-230 a tank. Sucks

[larryo340]

:hmmm: Geez
Don't you guys realize that miles per tank really has no value :nono: , The only true way to check economy is mile per gallon. I hope it does not have to be explained how to do this. Hell in even in my fathers '06 GM with fuel computer for MPG is wrong, but surprisingly close.

[jim geary]

Common guys. You all know why we don't get such great milage anymore.
Cause we tinkered with em. Plain and simple. And if your's is stock and untouched and gets rotton milage than I'd ask for a refund.

[RUSTY]

Common guys. You all know why we don't get such great milage anymore.
Cause we tinkered with em. Plain and simple. And if your's is stock and untouched and gets rotton milage than I'd ask for a refund.



Or you made the mistake of telling your wife about the o/d button and she has it on for merging and passing and o/d off for highway driving.
I have now told her not to touch it.

[High-C]

04/18/07 - 18.13 MPG (city driving etc)

04/26/07 - 22.12 MPG (hwy/city driving)

4.10's and a lead foot...

[Raudermaster]

I only get 220-230 a tank. Sucks


See! He has more mods than I do, and still gets that much! I'm LUCKY if I SEE 200! And I don't even get on it that much to be honest with you. During the week I go to school one day a week (20 miles to and back) and then just putting around town driving casually. My work is only 5 minutes away from me and that's no biggie. I just want to know why mine sucks so I can resolve it.

[MENINBLK]

18 city
26 highway (@ > 65 mph)

[Raudermaster]

Still good, and still better than what I get.

[Paul T. Casey]

I'd lean toward driver input. If you're getting that kind of mileage and don't notice any poor driveability issues, it's got to be the pressure of the right foot. Oh yeah, mine with all my mods 21-23ish normally, just got 26 2 weeks ago rural highway. :banana:

[GreekGod]

from my 2003 MM owners manual...
<HR style="COLOR: #d1d1e1" SIZE=1><!-- / icon and title --><!-- message -->Page 198 of 2003 MM owners manual:

..." Fuel expense, frequency of fill-ups, or fuel gauge readings are NOT accurate as a measure of fuel economy."

page 199 and 200 continue with instructions for calculating proper estimates. Excerpts:

..."Use the same side of the same pump and have the vehicle facing the same direction each time you fill up."...

..."3. After at least three to five fill-ups"...

..."Keep a record for at least one month"...

A single tank fill-up can give an estimate for one tank only.

[Rider90]

Does anyone have tips on how I can get mine BELOW 11 MPG? I keep trying but it likes to hang right around 12.

[Paul T. Casey]

from my 2003 MM owners manual...
<HR style="COLOR: #d1d1e1" SIZE=1><!-- / icon and title --><!-- message -->Page 198 of 2003 MM owners manual:

..." Fuel expense, frequency of fill-ups, or fuel gauge readings are NOT accurate as a measure of fuel economy."

page 199 and 200 continue with instructions for calculating proper estimates. Excerpts:

..."Use the same side of the same pump and have the vehicle facing the same direction each time you fill up."...

..."3. After at least three to five fill-ups"...

..."Keep a record for at least one month"...

A single tank fill-up can give an estimate for one tank only.


That would infer one read the manual. I can make Misquamicut RI to Winchester VA on ONEtank. Still have more left as I think the most I put in was 16.5 gallons.

[Raudermaster]

I just don't know, I still think something is up/clogged. I can assure you that I'm not hammering it all the time.

[Paul T. Casey]

How does it run? Does it seem normal, or is it missing, bogging, or otherwise making some less than normal noise or power? You're mods, if anything, should yeild you a slight increase in mileage.

[Raudermaster]

Nothing anything of that sort. I don't know, I'm bummed.

[GreekGod]

MPT is an inaccurate way to measure.

Try MPG and then report back.

comprende?

[jabird56]

Enclosed is a chart showing my monthly average MPG, since I bought the MM 4 years ago.
It's interesting that my AVERAGE high is in the month of May while my AVERAGE low is in June.
It's also interesting that it seems that I have the most consistent mileage during the months of DEC and JAN, go figure.

[larryo340]

When the needle gets to 1/4 tank I fill up. If you are getting less than 10 MPG then complain, remember these are full size cars!
I know mine is just a GM, but I get 14-18 mixed driving and as must as 25 on interstate driving keeping it under 70MPH almost impossible to do in these cares, I get 21-22 MPG on interstate cruising 80-85PH

[RedMerc04]

Yeah, I really dont pay much mind to my exact MPG but mine pretty much sucks right now. This week im going to tackle my fuel filter and clean my K&N so ill keep my fingers crossed. Does anybody know when we should replace our Oxygen sensors? Im probably due.. 45,000 mi

[larryo340]

Yeah, I really dont pay much mind to my exact MPG but mine pretty much sucks right now. This week im going to tackle my fuel filter and clean my K&N so ill keep my fingers crossed. Does anybody know when we should replace our Oxygen sensors? Im probably due.. 45,000 mi
Some people say 50-60,000 miles, some say to replace them when they go bad. I still have my originals in my car '98 GM 140k, see post above for my mileage.

[RF Overlord]

Raudermaster and RedMerc04:

Sounds like you both have K&N-type filters that require periodic cleaning and re-oiling. If so, that type of filter is notorious for shedding oil onto the MAF, which is especially close to the airbox in a Marauder. Try using some of this (http://www.crcindustries.com/auto/content/prod_detail.aspx?S=Y&PN=05110) on the MAF and disconnect the negative battery terminal for about 15 minutes and see if that improves your mileage.

[RedMerc04]

Good call. Thanks

[Raudermaster]

Thanks RF! I'll have to order me a can and see if that helps. Since I have the JLT, the filter is way bigger than the K&N and wouldn't probably be surprised if the MAF is dirty. I mean, I don't really care about my gas mileage, it's just something that's been bothering me since some people with 4.10's get better mileage than I do.

[Raudermaster]

How about this stuff I just picked up.
http://www.gunk.com/product_images/LG_M4712_6.JPG

http://www.gunk.com/prodinfo/M4712_6.PDF

[larryo340]

just make sure that it won't harm the finish inside the throttle body

[MENINBLK]

How about this stuff I just picked up.

You should be buying THROTTLE BODY CLEANER.
There IS a difference...

[Raudermaster]

I'm not cleaning anything after the intake tube.....

[Paul T. Casey]

http://www.crcindustries.com/auto/content/prod_detail.aspx?S=Y&PN=05110
"This" is available at NAPA and probably at any other parts store. "This" works. I still believe if there's no drivability issues, it's your foot causing the poor mileage.

[Raudermaster]

Well, no "major" drivability issues, but there is a slight "rough" idle. How about the stuff I just bought today? I would rather use that first if I know it's safe on my MAF.

[Paul T. Casey]

Well, no "major" drivability issues, but there is a slight "rough" idle. How about the stuff I just bought today? I would rather use that first if I know it's safe on my MAF.

I don't know anything about that stuff. If it says it's safe for MAF (and I'd be sure it used those words exactly) then use it. The CRC is MAF cleaner. Take the MAF out, hose it down with the stuff, let it dry, and re-install. I'll be working in the Somerst area starting May 14. Maybe we can hook up.

[Raudermaster]

I just spray the MAF needle inside where it reads the temp. correct?

[RF Overlord]

Spray the entire innards of the MAF. Just be careful to not contact the hot-wire sensor with the spray tube on the can.

Like Paul Casey said, unless the stuff you bought specifically states that it's OK for use on a MAF, I wouldn't chance it. The good ol' days of just needing a can of carburettor cleaner to do everything are long gone. Now you need MAF cleaner, throttle body cleaner, intake cleaner...The CRC stuff is available at any NAPA and many other FLAPS.

[GreekGod]

Thanks RF! I'll have to order me a can and see if that helps. Since I have the JLT, the filter is way bigger than the K&N and wouldn't probably be surprised if the MAF is dirty. I mean, I don't really care about my gas mileage, it's just something that's been bothering me since some people with 4.10's get better mileage than I do.

Soooo, what is your miles per gallon? Have you ever even checked one tank yet?

[Raudermaster]

Thanks all. Ordered a can of CRC's MAF Cleaner from my speedshop and it will be in tomorrow morning. EVERY parts store I went to here has never heard of it, and all they offered me was TB Cleaner/Carb cleaner/Intake cleaner which I told them will not do it. I returned the other can I bought too.

[J-MAN]

Over 24MPG on a round trip from Detroit to Cleveland. No Mods. Turned 100K on the return trip. Keep yer foot out of it!:burn:

[Paul T. Casey]

Turned 100K on the return trip. burn:

Welcome to the club, now quit babying that thing and put some miles on it! ;)

[Raudermaster]

Just cleaned it with the CRC stuff. Will report back...

[ctrlraven]

When the needle gets to 1/4 tank I fill up. If you are getting less than 10 MPG then complain, remember these are full size cars!
I know mine is just a GM, but I get 14-18 mixed driving and as must as 25 on interstate driving keeping it under 70MPH almost impossible to do in these cares, I get 21-22 MPG on interstate cruising 80-85PH


Same here with the MPGs. I tend to always fill up at the same gas station so I don't mix fuel brands and I'll know when I get a tank of bad gas that way.

I clean my filter and MAF every 6 months or 12-15K miles. Just put in some NGK TR6IX plugs and bumped up the tire psi by 1 lb (36 lbs Front, 37 lbs Rear). I've seen a slight increase in mileage already. I have the same driving schedule every week so I can pick up pretty quickly when my MPG goes up or down.

To clean your MAF you can use CRC MAF Cleaner or CRC QD Electronic Cleaner which I have been using for years and isn't a special order thing and can be found just about any auto parts store.

[Raudermaster]

Except for around here, not sure why. I just filled up and I usually always go to the same gas station. I took down all the proper info to get my MPG. Just paid $2.99 for 93 :(.

[RF Overlord]

Just paid $2.99 for 93 :(.You're lucky...here on the Cape, 87 is up to $3.03...93 is $3.21.

This is :bs: in the extreme...

:censor: :down: :censor:

[kayzap]

I checked the MPG on both cars on the same route of Los Angeles to Yucca Valley and back averaging 70MPHish

2004 MM 23.6MPG
2004 CV LX Sport 25.7 MPG

I don't even want to discuss my in town MPG until I can control my right foot.

[Motorhead350]

Does anyone have tips on how I can get mine BELOW 11 MPG? I keep trying but it likes to hang right around 12.

Now thats great! :lol:

[Raudermaster]

Well, I filled up again today, and I recorded my past mileage, gallons it took etc. and I did the same today. Now, if I did it right, it says I'm only getting 14.1! That's terrible IMO for the amount of mods I have. Just to make sure I have it right, you take your first mileage from the first fill up, and subtract that from the mileage recorded on the 2nd fill up, then divide that by the number of gallons it took the 2nd time and that's it right? Or am I doing it wrong?

[Shora]

Well, I filled up again today, and I recorded my past mileage, gallons it took etc. and I did the same today. Now, if I did it right, it says I'm only getting 14.1! That's terrible IMO for the amount of mods I have. Just to make sure I have it right, you take your first mileage from the first fill up, and subtract that from the mileage recorded on the 2nd fill up, then divide that by the number of gallons it took the 2nd time and that's it right? Or am I doing it wrong?

Look, its really easy. Fill your tank to FULL. Reset the trip odometer. When you fill up again divide the miles driven by the gallons filled.

I.E.

Drove 275 miles. Filled 15.32 gallons. Equals 17.95 miles per gallon.

For the most accurate reading, try using the same pump at the same station. This step is overkill IMO but maybe it will help you.

[Raudermaster]

So, I figure I would put this in the thread I started since I think it's affecting my gas mileage still. I have Dennis' Cobra kit, if I get the standard use of the stock MM O2 sensors, they'll fit in the piping correct from his kit? Should I bother replacing the rear O2's?

[fastblackmerc]

Read the owners manual, pages 198 to 201 about fuel ecomnomy and how to calculate usage.

[Raudermaster]

That doesn't really answer my question? :dunno:

[Blk Mamba]

In the 70's when the big gas scare was on people became aware of gas mileage, and when they started to get poor gas mileage, they looked in all directions with no avail, then of course it was in the last place they looked, for about $10 buy a locking gas cap, and see if that helps.

[kamikaze2899]

You're lucky...here on the Cape, 87 is up to $3.03...93 is $3.21.

This is :bs: in the extreme...

:censor: :down: :censor:

Here in Honolulu Hawaii 92 is $3.66 a gallon. The other islands are up to about $3.80 or so. We're looking at being in the $4.00 range soon.

[Bradley G]

I just put 17.1 gallons in the Marauder, it traveled 289.9 miles on this much fuel .
I boosted it a few times, all rural driving, no highway .
I don't warm up the car and try to keep wasteful idling down to a minimum.

[Raudermaster]

I have an A with the door release gas cap, so no worries there.

[Blk Mamba]

I have an "A" and I can get in, and you would never know.

[Raudermaster]

Sorry, I don't want to try to break my gas door open.

[Blk Mamba]

I drove "AAA" for many years, and can be in, in seconds, no harm, it only takes a few moments to take a few gallons, you never know. Buy the cap.