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 Very bad mileage question

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carguyray



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Join date : 2016-03-20

PostSubject: Very bad mileage question   Wed Apr 13, 2016 11:21 pm

So I have only had my 94 REW for a couple months (and we LOVE IT!) but I find I'm getting 13-14mpg at BEST. even a trip home on the highway was about 18 and I hear of guys on here loving their 30 mpg highway and 20 in the city.

I have gone through the very good stack of receipts from the prev. owner and found it's been about 2.5 years since plugs, wires, cap (reman), coil, were replaced. I'm going to be heading on a long trip and towing about 4000 pounds from Chicago area to Portland, OR so I really don't want to get 6mpg in the process.

I'm ready to replace what I need to but curious if any of you have 'solved' something like this before.

I'm also curious if any of you can offer what mpg you get on towing on the highway.

Thanks to all.
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802



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Age : 56
Location : Vermont

PostSubject: Re: Very bad mileage question   Thu Apr 14, 2016 12:03 am

I hate to say it, but your mileage is not terribly out of spec.
There are plenty of mileage threads on here, with ideas worth trying before your trip; but I'd be skeptical that a claim of 30 mpg in these cars could be faithfully reproduced.
Driving habits may be more predictive than mechanical modification.
Just my experience. As we say, "YMMV."
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just me



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Join date : 2014-10-09
Location : Riverside, CA

PostSubject: Re: Very bad mileage question   Thu Apr 14, 2016 1:34 am

I was thinking my 93 TBI 5.7 was getting much lower mileage than it should but after checking the mileage in a V6 minivan I discovered the van only got a few more mpgs. I'm satisfied now that it is just the type of driving I do (car barely gets warmed up before I get to my destination) combined with the sad quality of gasoline in southern California. I can get up to a 2 mpg difference just by using different brands of gasoline so it must be the additive packages the different brands use, they all get the base gasoline from the same plants. I have noticed that Shell's nitrogen infused gasoline gets much lower mpgs than Chevron or the local no-names, at least for me.
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dmg4

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PostSubject: Re: Very bad mileage question   Thu Apr 14, 2016 5:53 am

I've had three different LT1 wagons: a 1995 Caprice, a 1996 Roadmaster, and now a 1996 Caprice.  None of them ever came close to 30 mpg on the highway.  The best I ever achieved was 24 mpg, and that was a freak trip at 55 mph.  I hate 55 mph.

At 80 mph on the interstate with 3 people in the car, my current ride gets 18 to 20 mpg no matter what fuel is in the tank.  If I slow it down 10 to 15 mph, I'll pick up another 1 to 1.5 mpg. You need to run them on a trip of 500 miles or more to get a reproducible measure of gas mileage. Less than than and you are measuring the point at which the auto shutoffs on gas pumps kick in.

Perhaps the 91 to 93 cars do a bit better, but if someone with an LT1 wagon is getting 20+ mpg in the city, they must inhabit cities much different from the ones I drive in.
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phantom 309

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PostSubject: Re: Very bad mileage question   Thu Apr 14, 2016 10:56 am

Always run premium fuel,. todays ethanol watered down stuff really inhibits fuel mileage,.

make sure you have good ignition,. new proper functioning O2's, a clean maf sensor,.and a functioning egr,. pump your tires up to max allowable pressure ( i run mine at 42 psi)

If you have 2:56's and you don't live in the flatlands,. pull it back to 3rd when climbing grades,.

Keep your speed to 60mph

you too can get 25+,.  anymore than that is internet BS, and strong tail winds,.

PS,. get your pcm tuned ,..
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Deadmanonduty



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PostSubject: Re: Very bad mileage question   Thu Apr 14, 2016 1:56 pm

I take my 94 Caprice Wagon on a family vacation every summer and if I fill it with non ethanol premium It averages 27.5mpg EVERY trip at 75-78mph with the cruise on.  Thats mostly highway and very few hard accelerations and the car is piled FULL of the kids crap, so its loaded down big time.  I'm running 2.93 gears.
I've done this trip 5 times now and its gets 27.5 MPG every trip.

running around town cuts it down to 15-18mpg depending how you drive it.
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carguyray



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PostSubject: Re: Very bad mileage question   Thu Apr 14, 2016 5:32 pm

Wow, Great info from all of you and thank you!

The last post re. 27.5 is what I've been hearing on other boards (and I'm sure we're all on all of them anyway) but I was using that as 'a baseline' when I bought the car so I was (am) shocked.

I will have my Mech. go over all the items above as part of the pre-trip prep, but I have to ask where/how does one get the PCM tuned and what does the tuning do? I know from my 06 Magnum there's a TON of tuning to do to the 'chips', but I didn't know there was anything like that for these beauties. Any info/direction will be appreciated!
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phantom 309

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PostSubject: Re: Very bad mileage question   Thu Apr 14, 2016 6:54 pm

Deadmanonduty wrote:
I take my 94 Caprice Wagon on a family vacation every summer and if I fill it with non ethanol premium It averages 27.5mpg EVERY trip at 75-78mph with the cruise on.  Thats mostly highway and very few hard accelerations and the car is piled FULL of the kids crap, so its loaded down big time.  I'm running 2.93 gears.
I've done this trip 5 times now and its gets 27.5 MPG every trip.

running around town cuts it down to 15-18mpg depending how you drive it.

your pcm tuned?
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jasonlachapelle

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PostSubject: Re: Very bad mileage question   Thu Apr 14, 2016 7:46 pm

as mentioned above, a pcm tune will help get the most out of today's gas. Phantom 309 mentionned premium because we can't get ethanol free regular (87) in Canada but we can get ethanol free 91. The slightly higher up-front price is offset by the better mileage.
Google it, and if you can get ethanol free gas close (ish) to where you live, get your car tuned for 87.

What gears are you running ? For mileage, the LT1 likes to be just below 2000 rpm.

No one is 30 mpg, unless they are using imperial gallons.
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Deadmanonduty



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PostSubject: Re: Very bad mileage question   Thu Apr 14, 2016 8:39 pm

phantom 309 wrote:
Deadmanonduty wrote:
I take my 94 Caprice Wagon on a family vacation every summer and if I fill it with non ethanol premium It averages 27.5mpg EVERY trip at 75-78mph with the cruise on.  Thats mostly highway and very few hard accelerations and the car is piled FULL of the kids crap, so its loaded down big time.  I'm running 2.93 gears.
I've done this trip 5 times now and its gets 27.5 MPG every trip.

running around town cuts it down to 15-18mpg depending how you drive it.

your pcm tuned?

You betcha! Brian Herter tune. I just added SLP headers and EGR Delete and proper tune, I'm curious to see the MPG results to compare. It won't be for a couple months tho til I get it on the highway for our trip.

I was running a stock LT1 with 2.93's, PCM tune, Cold air intake, Cat back, export pipes, stock manifolds, and car has 78,000 miles on it, so i'm not sure if opti was ever replaced or not.
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Deadmanonduty



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PostSubject: Re: Very bad mileage question   Thu Apr 14, 2016 8:39 pm

carguyray wrote:
Wow, Great info from all of you and thank you!  

The last post re. 27.5 is what I've been hearing on other boards (and I'm sure we're all on all of them anyway) but I was using that as 'a baseline' when I bought the car so I was (am) shocked.

I will have my Mech. go over all the items above as part of the pre-trip prep, but I have to ask where/how does one get the PCM tuned and what does the tuning do?  I know from my 06 Magnum there's a TON of tuning to do to the 'chips', but I didn't know there was anything like that for these beauties.  Any info/direction will be appreciated!

I have a 05 Magnum RT with 50,000 miles on it! Smile Love it for my daily driver!
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Dropkick_Eddie

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PostSubject: Re: Very bad mileage question   Thu Apr 14, 2016 11:59 pm

First off, I am obsessed with eco modding, but only when it's possible- Traffic & weather permitting. I've got a 94 caprice wagon with 40k miles, freed up exhaust +intake 2:56 with 225/75r15, all synthetic fluids through out drivetrain, premium non ethanol fuel and I've gotten over 28mpg about 5-6 different times during the summers on long flat highway trips. I've gotten 30+ twice! I grandpa it up to speed and do not let her downshift and never use the brakes... Ecomod-neutral off ramps etc... These are wide open highways at around 70-72mph. I usually drive through the night and during the week(less-no traffic;) If I drive with any congestion, traffic, dbag drivers or rain it's more like 20-22mpg:(

I also have a 94 RMW with 100k, same mods, tires, and rear end. Daily driver, I can get 23-26 mpg when eco modding, but normally around 18-20winter- 20-22mpgsummer on the highway(75-80mph)

and my wifes 94 towpack RMW(2:93) no mods yet, always gets 19-20mpg hwy no matter how I drive it No
I love the 2:56 rearend for most highway driving, but passing and hills kinda suck:( I agree driving habits have a lot to do with it as well, because when I'm passing people on the right and frustrated with traffic- all bets are off! Evil or Very Mad

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bigredwagon

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PostSubject: Re: Very bad mileage question   Fri Apr 15, 2016 12:50 am

Honestly 30 mpg is laughable.  It's a v8 from the nineties and weighs just shy of a Sherman tank.  

And where are you all finding non ethyl gas? I've traveled quite a bit as well as made multiple moves across the country of 1000 miles or so and I don't think I could count on one good hand the times I've found non additive gas.  

I am intrigued by the pcm tune idea, but wonder if it's even worth it for a near stock 94 with a $#!+ton of miles.

As per mpg I'm rolling about 20 hyw and in town...well my town is 99% 25 mph so I know I'm already screwed there so i have stopped caring.
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dmg4

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PostSubject: Re: Very bad mileage question   Fri Apr 15, 2016 6:05 am

Ethanol free gas is easy to find almost anywhere if you keep your eyes open, especially at 91 octane.  It's not heavily advertised because the market is minimal.  Check this website for a zoomable map of sources for the continental US.  See:  [You must be registered and logged in to see this link.]

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Dropkick_Eddie

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PostSubject: Re: Very bad mileage question   Fri Apr 15, 2016 7:43 am

Hahaha it is!  I hear you man.  I figured I'd catch some flack if I posted;)  Anyways, I work in North Dakota for two weeks at a time and travel from ND to WI(home) and down to family farm in central IL often(during summer.)   I put on easily 40-45k(90%hwy) miles a year in my wagons combined(mainly the DD).  I drive so much that I have all my favorite stops as well.  I will admit that I usually have a tailwind when traveling south & eastward.  Especially for my best results.  when I leave my town to drive my caprice south I fill up with premium and put put directly onto the highway, with zero traffic after 10pm I never have to accelerate or decelerate if I don't want too.  I always let gravity slow me down naturally on the few little hills I see and neutral down the larger one.  after 200-300 miles I'll coast off the highway in neutral and fill up... I literally barely even press the brakes one time total to stop at my favorite exit!  This is how I get my best results.  With my caprice, these are the pristine conditions where I've gotten the results. I'm also alone with nothing much but a tool bag and a couple guns.   I would also like to see what a tune could do!Smile  Trust me- I've had 100's more tankfuls that were 18-22mpg, especially in my daily driver heading west:(  The absolute worse I've had was driving to work, straight into a 40+mph blizzard headwind in ND a couple winters ago, that was 13mpg driving 65mph for 275m in the DD  pale   I'm just saying that it is possible, but it takes all the right conditions, machinery and patience.  I plan on installing a t56 and 3:73(if the wife allows) in the distant future and really see what I could do!  I should note that I only eco mod when the conditions are right for it, otherwise 90% of the time I drive fast and like to hear my exhaust roar just like normal wagon enthusiasts Cool
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Deadmanonduty



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PostSubject: Re: Very bad mileage question   Fri Apr 15, 2016 8:47 am

I'm not the expert but I always understood throwing trans in Neutral while moving is the quickest way to destroy it.

Non Ethanol fuel can be had in WI at SHELL, QUIK TRIP and MOBIL just to name a few major ones. Its everywhere, but you gotta open your wallet for premium.

My 27 MPG runs are always long highway pulls, but also include 70 miles of traveling thru little towns and stopping at the major intersections numerous time, but throttling away normally and also passing numerous slow cars.

The PCM tune picks up a ton of HP and makes the car a ton more fun to drive as it wakes up the horrible stock shift points!
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MalibuSSwagon



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PostSubject: Re: Very bad mileage question   Fri Apr 15, 2016 10:05 am

neutral to coast? Can't see how you are saving gas doing that...when the car is coasting the ECM shuts off the injectors, if you are putting it into neutral there will be no load and the engine will be idling, using fuel. Don't believe me? When I was tuning the TPI I put on my C10, I could see the injector pulse width drop to zero when descending hills in gear.

Good mileage is also largely the result of good driving habits. Went on a 3600 mile road trip a few years ago with my gf and a friend. When I was driving we were getting 35-36 MPG (99 Acura 2.3L 5 speed) at 70 with AC on. When my buddy drove that mileage dropped to around 30 or worse. I was like, dude you gotta work on that. He would hammer the throttle, his shifts were harsh, on the gas on downhills...not conductive to good mileage.
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jasonlachapelle

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PostSubject: Re: Very bad mileage question   Fri Apr 15, 2016 10:29 am

Dropkick_Eddie wrote:
I work in North Dakota for two weeks at a time and travel from ND to WI(home)

your location probably contributes... I got some amazing mileage out of my previous purple pearl metallic sedan (3.42, 27" tires) in the Canadian prairies. I would consistently get 24 mpg highway with my woody caprice (3.42 gears, 27"tires, 227 cam, LE2 heads, 3200 stall) in Manitoba at 75 mph.

The car has deceleration fuel cutoff. You don't need to coast in neutral. You can tweak DFCO spark retard in the pcm tables.
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phantom 309

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PostSubject: Re: Very bad mileage question   Fri Apr 15, 2016 2:25 pm

Dropkick_Eddie wrote:
 I plan on installing a t56 and 3:73(if the wife allows) in the distant future and really see what I could do!

that would be interesting,.

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Dropkick_Eddie

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PostSubject: Re: Very bad mileage question   Fri Apr 15, 2016 10:30 pm

ahh this is all good info.  I've always driven a lot of manuals through out my life and would take it out of gear and coast quite a bit.  This is the first time in forever I don't have a manual in my fleet Crying or Very sad I've heard differing opinions about popping her into neutral, as long as there's no load.  also, how else am I suppose to rev the glasspacks for the ladies? cherry   but if you guys say so, I'll try letting the trans slow me down from now on.  It's been a decade or two since I lost a tranny, but I would definitely like to avoid that if possible;)  I think a couple tunes are in the cards!  I'll have to find a tuning thread and get to it! Hey, if it's not too far off subject, what year pcm's will fit a 94?  I have 3 94's and have a pcm from a 9c1 but don't know the year. how do I tell what year it is?
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bigredwagon

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PostSubject: Re: Very bad mileage question   Fri Apr 15, 2016 11:41 pm

Got gas today and the results are in...

12 mpg.  All around town with 99% 25 mph zones, think there was maybe 20 miles of 45-55 on that tank.
Sadly, no burnouts or hot rodding either.
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jasonlachapelle

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PostSubject: Re: Very bad mileage question   Fri Apr 15, 2016 11:56 pm

What gears ? Not terrible considering it's city driving.
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bigredwagon

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PostSubject: Re: Very bad mileage question   Sat Apr 16, 2016 12:07 am

94 wagon w/ posi. So that's 2.9 or 2.7? I can't remember at the moment. Someone here knows for sure.
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jasonlachapelle

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PostSubject: Re: Very bad mileage question   Sat Apr 16, 2016 12:53 am

do you have the towing package ? regardless, I'd say 12mpg is not out of the ordinary for your use.
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Deadmanonduty



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PostSubject: Re: Very bad mileage question   Sat Apr 16, 2016 9:49 am

My 95 only makes 12-15 MPG if you run it all in town or short trips, so thats very believable.

Get it out on the highway and it will nearly double the mpg. You are starting and stopping a very heavy car and that takes fuel to get it moving, so its going to be thirsty.
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Dropkick_Eddie

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PostSubject: Re: Very bad mileage question   Sat Apr 16, 2016 11:39 pm

yeah my wagons do about the same if I stay in town.
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Woody Wood Beaver

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PostSubject: Re: Very bad mileage question   Sun Apr 17, 2016 11:42 am

Your EGR may be faulty, if their is a vacuum leak at the diaphragm level, or any vacuum leak for that matter, the first symptom will be poor fuel mileage. There is a real simple way to check it. In this section there is a post called "Solution to hesitation/stutter at acceleration and at cruise." it might solve your problem. Good luck!
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