13mpg? that's garbage.

[tnord]

checked MPG on my last tank (got about 375miles) and it worked out to only 13.5mpg. hell, i should get that towing. i did it the proper way by reseting the trip meter at last fill-up, then dividing that by the number of gallons required to fill up the next time at the same station, so my calculation isn't off.

 

i'm almost at 100k miles, and have already done the air/fuel filter, plugs, and wires. plugs and wires are OEM (and yes i did properly gap them), fuel filter is a wix, and air filter is a K&N.

 

i really think i should be getting much better mileage than that. i drive quite conservatively, so a lead foot is not the problem. where should i start my search to get this thing running right again?

[ken1mod]

checked MPG on my last tank (got about 375miles) and it worked out to only 13.5mpg.  hell, i should get that towing. i did it the proper way by reseting the trip meter at last fill-up, then dividing that by the number of gallons required to fill up the next time at the same station, so my calculation isn't off.

 

i'm almost at 100k miles, and have already done the air/fuel filter, plugs, and wires.  plugs and wires are OEM (and yes i did properly gap them), fuel filter is a wix, and air filter is a K&N. 

 

i really think i should be getting much better mileage than that.  i drive quite conservatively, so a lead foot is not the problem.  where should i start my search to get this thing running right again?

 

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What I can tell you about fuel mileage is that I get better. You don't mention what engine/equipment you have. 4wd costs big time, if you need it, great but even when not engaged, it costs. Lots of weight and machinery spinning uselessly costs big time.

 

Driving style. I had a cadillac some years back with fuel mileage read out. I routinely got 17 mpg. My wife routinely got 12 and my friend routinely got 19. coasting when you know you are going to stop at a light was a major mileage concept. If you go from gas to brake at lights without a pronounced coast period is going to cost big time.

 

My vehicle is a 2000 silverado 5.3 2wd. My average mileage in hilly country is 17. If your truck is in good shape mechanically and I assume it is, no codes, work on driving technique. By the way, firm acceleration does not cause poor mileage. firm acceleration, including feeding on the occasional rice burner is surprisingly ok.

 

In fact, too slow acceleration hurts mileage. getting the computer in the cruise mode is important.

 

Try extending the coast concept in your driving, I betcha a quarter you will see a 25% improvement in city/local mileage.

 

Ken

[tnord]

What I can tell you about fuel mileage is that I get better.  You don't mention what engine/equipment you have.  4wd costs big time, if you need it, great but even when not engaged, it costs.  Lots of weight and machinery spinning uselessly costs big time.

 

Driving style.  I had a cadillac some years back with fuel mileage read out.  I routinely got 17 mpg.  My wife routinely got 12 and my friend routinely got 19.  coasting when you know you are going to stop at a light was a major mileage concept.  If you go from gas to brake at lights without a pronounced coast period is going to cost big time.

 

My vehicle is a 2000 silverado 5.3 2wd.  My average mileage in hilly country is 17.  If your truck is in good shape mechanically and I assume it is, no codes, work on driving technique.  By the way, firm acceleration does not cause poor mileage.  firm acceleration, including feeding on the occasional rice burner is surprisingly ok.

 

In fact, too slow acceleration hurts mileage.  getting the computer in the cruise mode is important.

 

Try extending the coast concept in your driving, I betcha a quarter you will see a 25% improvement in city/local mileage.

 

Ken

 

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thanks for the advice, i do try and use those driving tips you mention, but i guess i'll try and do it more often.

 

my fault for not mentioning the model of vehicle, it's an 01 5.3L 4x4 Z71.

 

my real concern is that the truck is not mechanically sound, not the specific mpg i get. it's just that the mpg is a good indicator of how well the mechanicals are working. i've had the thing for 2 years now and iirc i used to get much better mileage. i've noticed a drop in performance specifically when towing. i'll be going to the exact same racetrack as 2 years ago, with exactly the same load (the same car on the same trailer), traveling the same speed as always, but the truck downshifts far more often, i read this as a loss of power. with the race season coming up (and it being warmer out so i'm willing to work on it), i want to get this sorted out before i start hauling my 4500lb load 500+ miles.

 

i know i've got an exhaust leak, but i wouldn't think it would affect the performance this much.

[pm26]

Did you try cleaning the injectors? You would be surprised what a difference that can make! If you want to go cheap route, buy some Chevron Techron fuel injector cleaner ($6 a bottle at Walmart). Use one bottle for each 8 gallons of gas in the tank and repeat for two tankfulls. You should see some difference afterwards.

[ken1mod]

 

What I can tell you about fuel mileage is that I get better.  You don't mention what engine/equipment you have.  4wd costs big time, if you need it, great but even when not engaged, it costs.  Lots of weight and machinery spinning uselessly costs big time.

 

Driving style.  I had a cadillac some years back with fuel mileage read out.  I routinely got 17 mpg.  My wife routinely got 12 and my friend routinely got 19.  coasting when you know you are going to stop at a light was a major mileage concept.  If you go from gas to brake at lights without a pronounced coast period is going to cost big time.

 

My vehicle is a 2000 silverado 5.3 2wd.  My average mileage in hilly country is 17.  If your truck is in good shape mechanically and I assume it is, no codes, work on driving technique.  By the way, firm acceleration does not cause poor mileage.  firm acceleration, including feeding on the occasional rice burner is surprisingly ok.

 

In fact, too slow acceleration hurts mileage.  getting the computer in the cruise mode is important.

 

Try extending the coast concept in your driving, I betcha a quarter you will see a 25% improvement in city/local mileage.

 

Ken

 

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thanks for the advice, i do try and use those driving tips you mention, but i guess i'll try and do it more often.

 

my fault for not mentioning the model of vehicle, it's an 01 5.3L 4x4 Z71.

 

my real concern is that the truck is not mechanically sound, not the specific mpg i get. it's just that the mpg is a good indicator of how well the mechanicals are working. i've had the thing for 2 years now and iirc i used to get much better mileage. i've noticed a drop in performance specifically when towing. i'll be going to the exact same racetrack as 2 years ago, with exactly the same load (the same car on the same trailer), traveling the same speed as always, but the truck downshifts far more often, i read this as a loss of power. with the race season coming up (and it being warmer out so i'm willing to work on it), i want to get this sorted out before i start hauling my 4500lb load 500+ miles.

 

i know i've got an exhaust leak, but i wouldn't think it would affect the performance this much.

 

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By the way, cold weather/short trips are hell on mileage. where do you live? the car always got better mileage in summer with a/c on (phx, az) than in winter with heat on.

 

I am not a mileage expert but I used to play with the mileage meter all the time.

 

My bet is your truck is in really good shape. Where is your exhaust leak? before or after the o2 sensors? A failing o2 sensor will really wreck mileage and performance. On the cadillac, the car accidentally got a load of leaded fuel. took out o2 sensor and this drove the mixture full rich. both mileage and performance collapsed. might be an area to look into.

 

ken

[Bish]

Don't forget if you live in an area that uses reformulated "winter" gas, you can expect a drop of 1-2mph every winter. I've tracked every tankful up to 162K for mpg and I can tell you the week they change the gas in Chicago! Also, if you notice a steady drop in mph, consider replacing your o2 sensors as mentioned by ken1mod. I noticed a steady drop in mpg over a year at around 75K. Replaced both pre-cat sensors and mileage went up 2mpg immediately. The o2 sensors can get lazy without setting a code and it definitely affects mileage.

[fossil]

How many miles on your truck?

Remember as your engine gets older it's getting more tired. Timing chains get sloppy and valves get gummed up from carbon/oil deposits due seepeage past the valve seals. This all leads to engine inefficiency.

If you've got a high miler, I'd consider replacing the timing chain at least. It's not too big of a job and can be done in an afternoon and will bring your valve train back to its original timing. I would assume that the PCM compensates for this but I would imagine it can only do so much and probably just goes to a default setting according to mileage.

[Elwood 2000]

My Silverado has the 5.3, autotrac with 3:73 gears, similar to yours. I get 13 with a mix of city and highway driving. Summer is a bit better, probly due to the gasoline formulation, but I only get 15.5-16.5 on the highway. I have done a complete tune up on my truck recently and have noticed no inprovement in milage, but it does seem to idle smoother. I do use Lucas injector cleaner once in a while too.

 

If you do get better milage, I would not expect much. These are trucks.

[tnord]

i used some injector cleaner when i first got the truck, but i suppose that was a waste since it was before i replaced the fuel filter. the redline stuff i used on my old integra worked well, i'll try it on the truck i guess.

 

i live in kansas city, i'm not sure if they change the formulation on fuel around here or not. my drive to work everyday is 10 miles and takes about 15-20 minutes of mixed highway/city driving.

 

i think you're on to something with the o2 sensor idea. i bought the truck with 72k miles on it, so they probably weren't replaced before i bought it. i've got 99,7xx miles on it now, so they probably do need to be replaced. my exhaust leak is at the header, and has been getting worse lately. it wasn't throwing a code, so i didn't think much of it, but i could see how it really could mess things up. are these trucks very particular about just what o2 sensor you put in there? usually you can get oem bosch ones for like $80/per, or parts-store ones for $30-$40. some cars really don't like the generic ones, some really don't care.

 

i still think i should be getting better than 13mpg, but if i don't, i can live with that. it's the reduction in performance that really concerns me.

[RyanbabZ71]

I average about 13-15 mpg city/highway driving. Normal highway driving is 15-17 (highest I seen was almost 20 in the mountains of NC). Its a 2000 with about 57K miles. Milage has stayed consitant from the day I bought it.

 

Unless you were getting 16-17 mpg and it dropped to 13 I wouldnt suspect anything major is wrong.

[ken1mod]

I average about 13-15 mpg city/highway driving.  Normal highway driving is 15-17 (highest I seen was almost 20 in the mountains of NC).  Its a 2000 with about 57K miles.  Milage has stayed consitant from the day I bought it. 

 

Unless you were getting 16-17 mpg and it dropped to 13 I wouldnt suspect anything major is wrong.

 

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If all else fails, I have seen a clogged cat cause the symptoms you describe.

 

Ken

[5.3almnblk]

So trying to get the truck to cruise mode when driving is best? Meaning a little firm acceleration from stop helps?

[Wingnut]

My Silverado has the 5.3, autotrac with 3:73 gears, similar to yours. I get 13 with a mix of city and highway driving. Summer is a bit better, probly due to the gasoline formulation, but I only get 15.5-16.5 on the highway. I have done a complete tune up on my truck recently and have noticed no inprovement in milage, but it does seem to idle smoother. I do use Lucas injector cleaner once in a while too.

 

If you do get better milage, I would not expect much. These are trucks.

 

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I average about 13-15 mpg city/highway driving.  Normal highway driving is 15-17 (highest I seen was almost 20 in the mountains of NC).  Its a 2000 with about 57K miles.  Milage has stayed consitant from the day I bought it. 

 

Unless you were getting 16-17 mpg and it dropped to 13 I wouldnt suspect anything major is wrong.

 

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That's about what I get. 13-14 city, and I've gotten over 20 on the highway, keeping under 65...But I won't be repeating that one, it takes too dang long to get from a to b

[fossil]

With vehicles that are OBDII compliant which pretty well includes anything built after 1996 you do not have to change out the o2 sensors unless they "throw a code"" as the system has the capability of knowing when they are not working properly.

[Bish]

With vehicles that are OBDII compliant which pretty well includes anything built after 1996 you do not have to change out the o2 sensors unless they "throw a code"" as the system has the capability of knowing when they are not working properly.

 

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You may not HAVE to change them but you have to be happy losing 1-2mpg if you don't. If you are losing that kind of mileage like I was, it should only take about 6K miles to pay for the sensors. If your mileage is not suffering, I agree that there is no reason to change them. They do get "lazy" over time and this will effect mileage even if a code is not thrown.