Help!!! What happend to my mpg???

Retep · Post by **Retep** » Tue Oct 19, 2004 5:53 am

A few weeks ago, I gave my truck a little TLC by changing the oil and filter, changed fluid in both differentials and transfer case, as well as changed the fuel filter. A day latter, I put new tires on. Unfortunately, my truck has rewarded my efforts in the form of lower mpg. I used to average 18 to 19 mpg on a 50/50 mix of city and highway driving. Now I am getting 16 to 17 mpg. This was a sudden change not a gradual one.

I don’t see any way that fresh drive line fluids could cause this, so I have ruled that out.
The new tires are the same size as the stockers. They may weigh a little more (I don’t know for sure) but certainly not enough to cause this. Also they are inflated properly. I have also ruled out the tires.
That leaves the fuel filter. Could I have gotten a bad one? I don’t remember the part no., but the brand is Puralater.

A few other items I considered was the K&N air filter. It has 16k miles on it without a cleaning. K&N claims up to 50k miles between cleanings and states that the dirt can be as thick as the wire mesh before cleaning is necessary. It is visually dirty, but no where near what they say it can be. I picked up a cleaning kit and will give that a try anyway.

I ran a bottle of Techron through it about 5000 miles ago. That is the only time I have put any fuel system cleaner of any type in it.

The truck has 26k miles on it and for the most part runs very well. There is no rough idle and only maybe a very slight loss in power and I do mean maybe as the old butt dyno has indicated no power loss.

Anybody have any ideas? Gas costs to much these days to be getting bad mileage.

Thanks,
Pete

barch97 · Post by **barch97** » Tue Oct 19, 2004 6:23 am

don't be so quick to discount the difference in the weight of the tires. I've noticed a difference of about 1.5-2 mpg since switching to steel wheels and heavier tires.

Retep · Post by **Retep** » Tue Oct 19, 2004 6:52 am

I know the Dueler Revo in a 235/75 weighs in at 34 lbs. unmounted. I don't know what a Wranger RT/S in the same size weighs.
If its from the tires, I guess I have to live with it. But I really think there is more to it than that.
Pete

Post by **HenryJ** » Tue Oct 19, 2004 7:01 am

Check you speedometer calibration.

Set the cruise on 85 and pass a cop, I'm sure He'll tell you exactly how fast you are really going.

A better idea may be to take a ride with a GPS, or find a local radar reader sign.

I'm betting the speedometer calibration is throwing your calculations off.

Retep · Post by **Retep** » Tue Oct 19, 2004 7:15 am

HenryJ wrote:I'm betting the speedometer calibration is throwing your calculations off.

I had thought that too. I did a check from my driveway to a road sign about 10 miles down the highway in both my wifes car and my truck. The trip odometers gave the exact same reading.
I did not change to a larger tire, so calibration should not be out of wack.

You know, this is the kind of milage I get with winter formulated fuel. I can't imagine that we have switched over already, but I guess it could be possible.

Thanks for your help.
Pete

Justin · Post by **Justin** » Tue Oct 19, 2004 10:40 am

I'd love to get 16-17. I'm getting around 14mpg right now and i definetly blame it on the BL and 31" BFG's. I have always found that Goodyears wear faster than most other tires. Even on my jeep, my goodyear GSA's didnt last very long. With the crew, the rts's didnt last long either. Maybe the diameter of the tire was smaller than the diameter of the current tires you have now resulting in less weight and it may have been easier for your truck to turn the goodyears?

jeff024 · Post by **jeff024** » Tue Oct 19, 2004 10:59 am

ok as for your new revos they are 29in. tall the goodyears were 28.8 revs per mile on revos 719 on GYs 716 air in the 2 are a bit diffrent also not sure how much these #s will make in a tank of gas but some im sure . i have the stock rts still and im gettin 19.96-20.76 miles to a gallon.

shrubs2000 · Post by **shrubs2000** » Tue Oct 19, 2004 2:30 pm

I have never gotten 19 - 20. It's always 17 - 18 max (I track it on a spreadsheet). I drive 70 - 75 mph though so I 'm not sure how much I would gain if I dropped to 65. If I did 65 on the freeway to work, Iwould get run over

F9K9 · Post by **F9K9** » Tue Oct 19, 2004 2:53 pm

I went one tank at 12.6 mpg. Took a road trip and drove conservatively and got over 20 mpg. Had blue hair old ladies passing me but, I was determined to find out what it was capable of.

jeff024 · Post by **jeff024** » Tue Oct 19, 2004 3:21 pm

i drive almost 200 miles per day on average bout 165 about 120 of it on highways that are 65-70 and i do mainly 70-85 mph and im always right around 20mpg best yet was 23.33 miles to a gallon that was around 25000 miles on my truck its now at 39000 and only 9 months old so i guess im on the high end of the mgp. also do u guys have bed covers that helps add about 1.5-2mpg

shrubs2000 · Post by **shrubs2000** » Tue Oct 19, 2004 3:26 pm

I'm all stock except for my bed cover and 4x4 sickers. I know the bed cover will help the mpg.

I wonder if the addition of stickers on the sides increased the drag

jeff024 · Post by **jeff024** » Tue Oct 19, 2004 3:38 pm

damn those stickers

im stock excect for the bed cover and an air raid intake (( exaust comes friday )) after her bath

barch97 · Post by **barch97** » Tue Oct 19, 2004 3:46 pm

jeff024 wrote:i have the stock rts still and im gettin 19.96-20.76 miles to a gallon.

3:42 rear axle ratio

shrubs2000 wrote:I have never gotten 19 - 20. It's always 17 - 18 max (I track it on a spreadsheet). I drive 70 - 75 mph though so I 'm not sure how much I would gain if I dropped to 65. If I did 65 on the freeway to work, Iwould get run over

3:73 rear axle ratio

check your glovebox rpo codes. One sticker that does make a BIG difference in performance.

jeff024 · Post by **jeff024** » Tue Oct 19, 2004 3:48 pm

i have the 3.73

barch97 · Post by **barch97** » Tue Oct 19, 2004 3:51 pm

jeff024 wrote:i have the 3.73

hmm... maybe it's an octane thing? I've noticed a substantial increase in fuel efficiency when using higher octane gas. About 2mpg difference between 87 and 89. I haven't been able to afford a tank of 91 in a long time. so, not sure if the increase is proportional.

jeff024 · Post by **jeff024** » Tue Oct 19, 2004 3:57 pm

i would say 75% i run 87 and then 89 or 93 not sure why i get more mpg but maybe u need ur injectors cleaned

Retep · Post by **Retep** » Tue Oct 19, 2004 4:50 pm

jeff024 wrote:ok as for your new revos they are 29in. tall the goodyears were 28.8 revs per mile on revos 719 on GYs 716

I have the p-metric size Revo's which according to Bridgestone's web site, measure 28.9" dia and 721 rev per mile. The 29" dia. size is the lt-metric.
Anyway, the size difference is almost a non-issue and can not be the cause of my mpg loss. There could be a substantial difference in weight though, which would certainly have an affect. I wish I could find what the GYears weigh so I could either rule it out or have at least part of my answer.

I am still convinced I have something else going on. I keep wanting to blame the new fuel filter. If I don't see an improvement after I clean and re-oil the K&N air filter, I will probably try another fuel filter.
If neither of these work maybe I will take it to the dealer and have them check it.

jeff024 wrote:...im gettin 19.96-20.76 miles to a gallon.

That is the kind of milage I used to get on highway trips. I took a small (a little over 100 miles) all highway trip with an average speed of 70 mph this past weekend and got only 18.2 mpg

shrubs2000 wrote:...If I did 65 on the freeway to work, Iwould get run over

Yeah, I know what you mean. I am pretty sure you and I drive the same stretch of I675 everyday. I try to keep it between 70 and 75 mph, but sometimes find myself doing 80 just to keep up.

Thanks all,
Pete

malkavian · Post by **malkavian** » Tue Oct 19, 2004 10:17 pm

not to start up the old octane argument. But octane rateing is just the resistence to detenation. A fuel with a lower octane rateing actually burns stronger and will actually give better fuel economy. Ill have to dig out my books on octane rateings and the such. I researched this extensivly when I built my 383 mini ram with mulit port nitrous injection.

Maximous · Post by **Maximous** » Tue Oct 19, 2004 11:36 pm

i have to agree, the way my uncle who is a head mangager type guy at the local shell refinery type place told me that the main difference in the characteristics between the two ends (87-93) is the storage life, i was told for something like say a jet ski, run 87 all summer except for the last few fill-ups, that way when you store it it is full of 93 including all the lines and anywhere feul hangs out with all the other fuel, 93 stores better, its like using "stabil" you know, the stuff Paul Harvey promotes

shrubs2000 · Post by **shrubs2000** » Wed Oct 20, 2004 12:38 am

Retep wrote: Yeah, I know what you mean. I am pretty sure you and I drive the same stretch of I675 everyday. I try to keep it between 70 and 75 mph, but sometimes find myself doing 80 just to keep up.

Yep, same raceway!

I'll have to check and see what gears I'm running when I head out to work.

Forrest

Post by **HenryJ** » Wed Oct 20, 2004 3:32 am

malkavian wrote:not to start up the old octane argument. But octane rateing is just the resistence to detenation. A fuel with a lower octane rateing actually burns stronger and will actually give better fuel economy....

True if there is no detonation occuring. If the rating is too low for the compression ratio, detonation occurs and the PCM retards the timing to compensate. The result is less mileage and performance.

So use as low an octane rating as possible without detonation. Watching the knock count using Autotap is a great way to visualize this.

shrubs2000 · Post by **shrubs2000** » Wed Oct 20, 2004 1:27 pm

OK... where do I find my gear ratio on the truck? It's not on the glove box sticker or the doors.

I did find it on my original dealer sticker. I have 3.42 gears.

adrenalnjunky · Post by **adrenalnjunky** » Wed Oct 20, 2004 1:42 pm

It's on the sticker in the glovebox

all of those 3digit codes are RPO codes - Regular Production Order.

Each code signifies a component or assembly in your vehicle.

You say you have 3.42, the you'll have RPO code GU6
If you had 3.73's you'd have RPO code GT4
If you have the locker int he rear, you'll have RPO code G80

You can find the RPO code search engine Here:
RPO Codes

shrubs2000 · Post by **shrubs2000** » Wed Oct 20, 2004 2:39 pm

Darnit! Now I'm going to have to print the codes out and look them all up!!! j/k (really though I will look them up)

Great info and thanx for the site!

24digger · Post by **24digger** » Wed Oct 20, 2004 6:05 pm

I think you guys have forgotten about the winter gas formula. My wifes cavalier dropped 3mpg and both my truck have dropped as well.

Ken · Post by **Ken** » Wed Oct 20, 2004 7:07 pm

Retep wrote:A few weeks ago, I gave my truck a little TLC by changing the oil and filter, changed fluid in both differentials and transfer case, as well as changed the fuel filter.

I don’t see any way that fresh drive line fluids could cause this, so I have ruled that out.

Did you replace those fluids with the same weight / viscosity as what was in it originally?

Retep · Post by **Retep** » Thu Oct 21, 2004 5:26 am

Ken wrote:Did you replace those fluids with the same weight / viscosity as what was in it originally?

Yes.

24digger wrote:I think you guys have forgotten about the winter gas formula. My wifes cavalier dropped 3mpg and both my truck have dropped as well.

I thought about that as well. But do we really change to winter formula gas in early October?

Pete

Ken · Post by **Ken** » Thu Oct 21, 2004 6:57 am

24digger wrote: I thought about that as well. But do we really change to winter formula gas in early October?

Pete

In AZ they start switching over in Oct.

kf6kmx · Post by **kf6kmx** » Thu Oct 21, 2004 7:08 am

Retep wrote:I know the Dueler Revo in a 235/75 weighs in at 34 lbs. unmounted. I don't know what a Wranger RT/S in the same size weighs.
If its from the tires, I guess I have to live with it. But I really think there is more to it than that.
Pete

Oh no

Those are the Revos I have on order.. they should be in tonight or tomorrow.. hope they arent dropping the mileage..
Guess I'll be able to tell you in about 24 to 48 hours.. I get 18 city/hwy mix with my stock Laredo's on stock rims.. I'm keeping the stock rims, for now anyway... we'll see what happens..

kf6kmx · Post by **kf6kmx** » Thu Oct 21, 2004 7:12 am

shrubs2000 wrote:I have never gotten 19 - 20. It's always 17 - 18 max (I track it on a spreadsheet). I drive 70 - 75 mph though so I 'm not sure how much I would gain if I dropped to 65. If I did 65 on the freeway to work, Iwould get run over

I drive country roads to get to the air base (I come in the back gate, closer to our building, and a direct run from my house, 20 miles away)..

I have found that on my stock wheels (Laredo.. did everyone else get goodyear from the factory or something??) I get my best mileage right at about 58 to 62mph.. I drop a good 1-2mpg per tank if I up it to 70.. I guessing its the gearing..

kf6kmx · Post by **kf6kmx** » Thu Oct 21, 2004 7:19 am

jeff024 wrote:i drive almost 200 miles per day on average bout 165 about 120 of it on highways that are 65-70 and i do mainly 70-85 mph and im always right around 20mpg best yet was 23.33 miles to a gallon that was around 25000 miles on my truck its now at 39000 and only 9 months old so i guess im on the high end of the mgp. also do u guys have bed covers that helps add about 1.5-2mpg

Best I've gotten was about 23.8.. I filled up in Paso Robles, drove Hwy 41 straight to Lemoore and filled back to see pure hwy..

Ken · Post by **Ken** » Thu Oct 21, 2004 7:27 am

kf6kmx wrote:
shrubs2000 wrote:I have never gotten 19 - 20. It's always 17 - 18 max (I track it on a spreadsheet). I drive 70 - 75 mph though so I 'm not sure how much I would gain if I dropped to 65. If I did 65 on the freeway to work, Iwould get run over
I drive country roads to get to the air base (I come in the back gate, closer to our building, and a direct run from my house, 20 miles away)..

I have found that on my stock wheels (Laredo.. did everyone else get goodyear from the factory or something??) I get my best mileage right at about 58 to 62mph.. I drop a good 1-2mpg per tank if I up it to 70.. I guessing its the gearing..

I thought I was getting poor milage but it sounds like I'm doing ok. I took a trip a few weeks ago (Approx 260 miles round trip) a large percentage of that was on interstate and over some fairly good sized mountains. I drove 70 -80 MPH the entire trip and there was a small amount of city driving. Round trip though I got 19.2 MPG. Which didn't sound very good until I heard what you were getting. I have stock ZR5 wheels and tires (Goodyears) and I just recently (July) changed all fluids out to full synthetic.

Retep · Post by **Retep** » Thu Oct 21, 2004 9:41 am

kf6kmx wrote:Oh no Those are the Revos I have on order.. they should be in tonight or tomorrow.. hope they arent dropping the mileage..
Guess I'll be able to tell you in about 24 to 48 hours.. I get 18 city/hwy mix with my stock Laredo's on stock rims.. I'm keeping the stock rims, for now anyway... we'll see what happens..

Scott, Don't sweat the tires. As I have stated before, I don't think that is the issue. And if it is, then that just makes the Revo a little more of an expensive tire. Still a great tire. But please do let me know if you get any kind of change in mileage after you get them.

Pete

kf6kmx · Post by **kf6kmx** » Thu Oct 21, 2004 11:45 am

Retep wrote:
kf6kmx wrote:Oh no Those are the Revos I have on order.. they should be in tonight or tomorrow.. hope they arent dropping the mileage..
Guess I'll be able to tell you in about 24 to 48 hours.. I get 18 city/hwy mix with my stock Laredo's on stock rims.. I'm keeping the stock rims, for now anyway... we'll see what happens..
Scott, Don't sweat the tires. As I have stated before, I don't think that is the issue. And if it is, then that just makes the Revo a little more of an expensive tire. Still a great tire. But please do let me know if you get any kind of change in mileage after you get them.

Pete

I'm not sweating the tires.. I want the taction! Thats more important than a slight fuel change (although the way its getting around here the is no SLIGHT fuel anything..) Just paid 2.479/gal for the low-end octane.... ugh..
I told someone last night, if it stays at the rate it is going, we'll be paying $3/gal by Christmas! this is nuts.. where are the people who were crying 'price gouging' when it hit 2.12/gal... now they aren't saying a word... We're paying about .50/gal MORE than the national avg here in this part of this lousy state, with their ridiculous tax rate on the gas, and the custom california 'mix' on the fuel they make us burn, year round..

jeff024 · Post by **jeff024** » Thu Oct 21, 2004 1:51 pm

ouch 2.01 here in maryland for 87.ok i picked up about 2 more mpg with an exaust upgrade so im now pretty much at about 21-22 mpg all the time but i just put it on lastnight and sounds great and a bit more power.not sure if it makes any diffrence but i have only used Pennzoil® SUV, Truck and Minivan Motor Oils
Enhanced Protection
Synthetic Blend and the same gos for any other fluids that can take a Synthetic maybe thats why im on the high side of the mpg

gocntry · Post by **gocntry** » Thu Oct 21, 2004 2:40 pm

$2.01 Ouch!......$2.49 Double Ouch....I Filled Up At Costco Today In Manassas Va. $1.88 For 87....I Thought That Was Gettin High......

jeff024 · Post by **jeff024** » Thu Oct 21, 2004 2:44 pm

yup gas is cheaper in VA i get it at the gas station across the bridge goin in to cherlestown wva or leesburg

kf6kmx · Post by **kf6kmx** » Fri Oct 22, 2004 5:13 am

gocntry wrote:$2.01 Ouch!......$2.49 Double Ouch....I Filled Up At Costco Today In Manassas Va. $1.88 For 87....I Thought That Was Gettin High......

Last time it was $1.84 here was 2/14/04 (looked it up in my gas mileage program...)
It crossed the $2 mark in March and has never gone below 2.04/gal since

jeff024 · Post by **jeff024** » Fri Oct 22, 2004 11:03 am

that just makes no sence to me how we all use the same gas and it can reach over 2.50 a gal in ca and not on the east coast.

Justin · Post by **Justin** » Fri Oct 22, 2004 11:04 am

look at the price of desiel....$2.33 a gallon here in RI. After looking at stocks, the price of crude oil jumped up another $.50....Weather experts expect a cold winter so all the stock market guru's went to town.

Post by **HenryJ** » Fri Oct 22, 2004 11:07 am

jeff024 wrote:that just makes no sence to me how we all use the same gas and it can reach over 2.50 a gal in ca and not on the east coast.

Doesn't CA require oxygenated fuel, and additives to reduce vehicle emissions?

That may be their "excuse" for the higher prices?

I know we hear the old "trucking expenses" to deliver the fuel here lead to the higher prices.

Uhmmm , RRright!

Post by **Walt** » Sat Oct 23, 2004 7:36 am

I just filled up this morning on my way to work for $1.69/gallon

jeff024 · Post by **jeff024** » Sat Oct 23, 2004 9:33 am

Hmmm my fillup yesterday was 31.00 at 2.02 per gal

shrubs2000 · Post by **shrubs2000** » Sat Oct 23, 2004 11:30 am

1.88 here today....

F9K9 · Post by **F9K9** » Sat Oct 23, 2004 11:41 am

AAAAaaaaaaaaaaarrrrrrrrrrrrrrrrggggggghhhhhhhhhh

Just filled filled up with 89 octane at $2.09 and I shopped around.

Wanted to see if it will "ping" with my HPPIII set for 103 octane before I revert back to the 87.

I do find it humorous that we all are concerned with the price of gas but, don't worry about spending money on mods

I, for one am guilty of it

jeff024 · Post by **jeff024** » Sat Oct 23, 2004 9:34 pm

yes but the mods are something you dont mind paying for the gas we all do , unless we can get the mods for free:)

Maximous · Post by **Maximous** » Sat Oct 23, 2004 9:42 pm

i just thought about this, (sorry of topic) Oscar Wilde was a great man, very smart, however he got it wrong, work is not the curse of a drinking man, Kuwait is

Retep · Post by **Retep** » Wed Oct 27, 2004 6:31 am

Update:
I ran a paper air filter while I had the K&N out for cleaning, drying, and oiling. I got 17.0 MPG over five days of my daily commute. Not a big improvement and certainly not what I used to get. K&N was put back in this morning, I will see how that goes.
Thinking of trying an OEM fuel filter. Anyone know the part no. for an AC Delco fuel filter.

Pete

kf6kmx · Post by **kf6kmx** » Thu Oct 28, 2004 9:02 pm

Retep wrote: But please do let me know if you get any kind of change in mileage after you get them.

Pete

First tank with the new tires.. Dropped about 3/4 mpg.. BUT, we had 2 days of very bad storms with high winds and rain, plus I did a little 4x4 to try the tires in a little mud

I'll know more after a couple tanks ruin through and I casn get a true avg, but I'm guess maybe a 1/4 to 1/2 mpg drop going up to the Revo.. but they are definetly worth it!

Retep · Post by **Retep** » Fri Oct 29, 2004 5:51 am

kf6kmx wrote:
Retep wrote: But please do let me know if you get any kind of change in mileage after you get them.

Pete
First tank with the new tires.. Dropped about 3/4 mpg.. BUT, we had 2 days of very bad storms with high winds and rain, plus I did a little 4x4 to try the tires in a little mud

I'll know more after a couple tanks ruin through and I casn get a true avg, but I'm guess maybe a 1/4 to 1/2 mpg drop going up to the Revo.. but they are definetly worth it!

Thanks for the update Scott.

S-10CREWCAB.NET

Help!!! What happend to my mpg???

Help!!! What happend to my mpg???

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Re: Help!!! What happend to my mpg???

Re: Help!!! What happend to my mpg???