Sudden Fuel Mileage Drop

[KARNUT]

3 hours ago, elcamino said:

22-24 is unrealistic I don't care what the onboard readout says.  The ONLY sure method to calculate mileage is by logging miles and fuel used over thousands of miles and then averaging it out.  Taking one snapshot in time and using that as gospel is flawed as these in-vehicle average MPG displays are almost always inaccurate..  If those figures were true (22-24mpg) than GM would be claiming that mileage on the window sticker like on this 2022 Silverado equipped similar to yours. 

 

 

 

2022

I’ve been waiting about 5 years for someone to make this point other than me. I’m already on his ignore list. Questioning  some of the facts. The other fact that’s often mentioned is all those vehicles that have 1 million plus miles. I spent my life driving I’m at maybe 2 million. I’ve owned over 15 trucks for work. 

Edited January 10, 2022 by KARNUT

[Grumpy Bear]

4 hours ago, elcamino said:

 The ONLY sure method to calculate mileage is by logging miles and fuel used over thousands of miles and then averaging it out. 

 

Yep, every tank since birth. 155K of hand calculated records.

Summer tanks above the yellow life time and winter tanks below.

Orange line the year over year improvement with adjustments and choices.

As I said. I don't guess.

 

 

EPA sticker on this unit said 24 Highway, 17 City and 20 Combine

It's not just realistic, it can be beaten.

 

 

 

[Grumpy Bear]

Here's a thought. If ones practice is to run 150K and never MEASURE then what is offered is opinion as to the condition of the unit being bragged about. You have no data if you don't measure. Good fortune IS NIETHER facts nor data. 

 

If you like to read the data and ignore it then that is just......  What's the word?

And the reasons people get ignored. 

 

 

[scralatchtica824]

1 hour ago, Grumpy Bear said:

Here's a thought. If ones practice is to run 150K and never MEASURE then what is offered is opinion as to the condition of the unit being bragged about. You have no data if you don't measure. Good fortune IS NIETHER facts nor data. 

 

If you like to read the data and ignore it then that is just......  What's the word?

And the reasons people get ignored. 

 

 

Grumpy Bear, I've seen you post in almost all of the threads I've read on here. (I'm jealous I wish I had that much time! haha) Your knowledge always seems to be based on your own personal experience and is demonstratable with hard data you have gathered and calculated.

 

Thank you for the input on everything in the thread and I'm sure other threads that myself and others create!

[pokismoki]

13 hours ago, Grumpy Bear said:

 

Somewhere in my build thread I found that my factory 'in spec' alignment while in spec was all over the map within those specs. When I fixed that...WOW!! Largest single gain in mileage from any one enhancement. Worth ever penny I spent so now I check it about once a year and keep it perfect. 

got a link to your adjustments?

i wanna see what you changed

[voided3]

One other possible factor that I don't believe was mentioned could be a change to winter blend gas, though I believe the winter blend starts being available in early fall so perhaps you were already running on it prior to the modifications. I figured I'd throw that out there as another factor.

[Grumpy Bear]

1 hour ago, pokismoki said:

got a link to your adjustments?

i wanna see what you changed

 

You want the link to my build thread? 

 

 

Maybe I'm not sure what your asking for. I just posted the before, after and intermediate alignment sheets. Page #1 of this thread. 

 

Unless you asking what I changed in the suspension itself?

 

Bell -2" knuckles and King OEM coil overs with 600# springs substituted for the delivery 750# springs. And a set of MOOG camber/caster cams. 

 

 

This alignment was pre King Install but after fixing the awful factory set up shown on page #1.

 

 

From those corrected adjustment the installation of the total suspension moved it from the first 'good' numbers above to this mess below. 

 

 

Deaver 11 leaf springs with 2" less arch and 15% less rate in Sulastic hangers and dampened by King shocks.  OEM spacer removed and pinion angle checked but without need for any adjustment. 

 

 

Or are you asking for an explanation of the adjustments on the final alignment below?

Post install and alignment. 

 

I can if you like. 

Just say. 

 

 

[16LT4]

Winter gas really is a farce excuse.  If it decreased fuel economy, then the same lowered fuel economy would be present when temperature swings unseasonably warm.

 

My truck has averaged a best of 26.5 mpg from Florida to NY, cruise control set to 68 mph on I-95.  The on-board display was off by 0.5 mpg.  I calculate economy with every fill-up, and the dash is always within 1mpg of the calculated value, sometimes actually showing less than calculations.  However, even calculations are not entirely accurate due to a few variables, such as 1) the station pump click-off pressure 2) the amount of fuel added after the click-off 3) temperature when previously filled with fuel 4) temperature when re-fueled.  OnStar data using the phone app shows a lifetime mileage of 30.5 mpg, most of which obtained by the original owner of the truck.  Given the computer is nearly the same as a calculator, that is quite good.  

 

My absolute BEST fuel economies are in early spring and mid-autumn: my weekend job commute is nearly 200 miles each way, and I fill up when I leave my home area, and again when I arrive.  I use the same gas stations, travel the same roads, drive the same way, etc. to reduce variables.  During those specific seasonal times, my fuel economy is up to 8mpg higher than normal, based on the vehicle (best is on the '11 Jetta), but EVERY vehicle sees an increase.  During those seasons, ambient temperature swings can be as high as 30*F between the fuelings that book-end the trip, and the drastic mpg improvements are ONLY when there is a large temperature swing; on days within those seasons where there isn't a large temperature delta, fuel economy suffers.  I've recorded better fuel economy on "winter fuel" than "summer fuel" in those seasons.  Why?  The fuel in the tank when I leave might be in the 30*F's or 40*F's, but when I arrive 3 hours later, 20*F hotter or more.  Fuel expands when heated, so my hypothesis is that the expanded tank fuel limits the amount that can be added to the tank, giving a false economy increase.  Particularly in the VW, if the car then was parked (I keep another car at my other house for work when I'm there), the fuel gauge can read full when parked, but read lower the next day if checked when cold.  If checked later than afternoon after warming all day, it magically read full again.  Yesterday on my trip back North in the BMW, the fuel gauge didn't seem to move much at all, adding nearly 20 miles to each 8th tank, yet the computer's mpg read-out didn't match the fuel gauge, reading much less.  On that car, the gauge is as reliable as a clock, and has been for 185k miles.  What happened?  It was 20*F when I left and 40*F after 2 hours of the drive; once I got upstate and temperatures dropped into the low 30*s again, the gauge needle started moving much faster.

 

Cold weather reduction in fuel economy: 1) use of remote start 2) increased "warm up" time (I never do this) 3) running a rich fuel mix to start the engine (engines still have to "choke" to start when cold) 4) increased time spent running in open-loop rich mode before getting to operating temperature or switching to closed loop 5) cold air is denser than warm air.  Dry air is denser than wet air.  Cold/dry air much denser than warm/moist air.  It takes more energy to punch a brick of a truck through dense winter air than light summer air 6) even in closed loop, the PCM meters additional fuel to maintain stoich given data obtained by various MAF, baro, and IAT sensors 7) increased friction of ALL the fluids; transfer case and differential(s) are heated solely by friction, unlike the transmission and engine oils which can be heated by coolant and radiant heat from the exhaust manifold.

 

Oh, and don't forget fuel station.  My cars always get worse mileage using BJ's "premium"... given the low price, I suspect their 91 isn't really 91.  

[pokismoki]

2 hours ago, Grumpy Bear said:

 

You want the link to my build thread? 

 

 

Maybe I'm not sure what your asking for. I just posted the before, after and intermediate alignment sheets. Page #1 of this thread. 

 

Unless you asking what I changed in the suspension itself?

 

Bell -2" knuckles and King OEM coil overs with 600# springs substituted for the delivery 750# springs. And a set of MOOG camber/caster cams. 

 

 

This alignment was pre King Install but after fixing the awful factory set up shown on page #1.

 

 

From those corrected adjustment the installation of the total suspension moved it from the first 'good' numbers above to this mess below. 

 

 

Deaver 11 leaf springs with 2" less arch and 15% less rate in Sulastic hangers and dampened by King shocks.  OEM spacer removed and pinion angle checked but without need for any adjustment. 

 

 

Or are you asking for an explanation of the adjustments on the final alignment below?

Post install and alignment. 

 

I can if you like. 

Just say. 

 

 

 

 

I'de love an explanation of your adjustments... I will have to pull my alignment sheet so I can compare numbers..

those rear leaf springs look amaizing, i'll check out your build page for more details on those

[scralatchtica824]

I picked the truck up post alignment. Only 1/2 mile ride home to the house it already feels like it glides better. I’ll drive a bunch more and get more accurate data.

Edited January 10, 2022 by scralatchtica824

[scralatchtica824]

After alignment the truck doesn't necessarily pull but the wheel is off to the left to keep the truck straight. That makes sense with a -0.53 thrust angle. I'm wondering if I can loosen the rear axle and center pin, use a block of wood and smack it straight-er.

[CamGTP]

No, don't do that. Just take it back and have them re-center the steering wheel. They will have to perform another caster/camber swing, measure the toe and put the steering wheel straight and re-adjust it again.

 

I've had to do that many times. My version of straight isn't what the customers was. Or someone during the job the vehicle got bumped or I moved it during the work without noticing.

[Grumpy Bear]

4 hours ago, pokismoki said:

 

 

I'de love an explanation of your adjustments... I will have to pull my alignment sheet so I can compare numbers..

those rear leaf springs look amaizing, i'll check out your build page for more details on those

 

Okay let's pull it up again. 

 

 

Let's start with castor. The middle one. It's always positive. The drivers side is always a tab more positive than than the passenger side but not more than a quarter degree. This machine however only measures in tenths so 2 to 3 tenths. See the range? The less castor you have the less violent the 'hit' on a bump and the less bump steer it reacts to. The more positive it is the more it wants to stay straight. Which is fine until you wish to change direction. Feel! 1 to 2 degrees is plenty and keeps the steering light and responsive and the 'hit' light.  

 

Camber. Ditto. Drivers side more positive than the passenger side and since we are using negative camber more positive means less negative. Right? I like to be on the negative side when weigh bias is forward as is the case in most front engine configurations. In a pickup with a straight rear axle it's more important IMHO as a bit negative helps keep the nose from rolling the tire past neutral in most normal driving. Positive camber is more of a luxo boat float. 

 

Those two together keep the drivers side tire from 'climbing' the roads natural 'crown'. Road is always higher in the center than the at the curbs. With this set up and electronic power steering natural 'dampener' so rolles straight down th road hands off the wheel and will nose into a turn without input. A second reason for negative camber. Keep it from getting to tight. Loose cars scare passengers. Tight cars scare drivers. No one likes the wall. 

 

A hair positive toe counters the negative camber wear tendency and keeps the shimmy at bay when you hit a bump. It is imperative that they are DEAD equal. 

 

All my road adjustments are darn near neutral which limits 'drag' thus the crazy rolling distance and economy enhancement. 

 

I strive for zero thrust angle and zero steer ahead. Under 1/10 degree is hard to notice from the rear and hard for the driver to sense in the seat. I settled on zero steer ahead and 0.04 thrust. 

 

Hope that is helpful. BTW notice scralatchtica824 alignment sheet. The factory target values reflect my specs as to differences between left and right sides. 

 

Many shops with a machine do not care if it is right. Only that it is IN spec. And that no matter how much they charge. this is where the personal relationship with a guy who KNOWS HOW is handy  

[Grumpy Bear]

5 hours ago, pokismoki said:

those rear leaf springs look amazing, 

 

Thanks. The greater the number of leaves for the rated load the more 'compliant' the spring is. It also gives you some ability to fine tune the load and ride height. Somewhere in that mess of 50 pages is a picture of that springs custom part number. Fits trucks 2007 to the end of K2 classic. 

 

I have 1/8" wedge left rear in this truck to keep it dead level. 

 

Something I did not mention in the alignment rant. When you level you change the castor by the exact amount of the difference in frame angle. (rake). 

[scralatchtica824]

49 minutes ago, Grumpy Bear said:

 

Okay let's pull it up again. 

 

 

Let's start with castor. The middle one. It's always positive. The drivers side is always a tab more positive than than the passenger side but not more than a quarter degree. This machine however only measures in tenths so 2 to 3 tenths. See the range? The less castor you have the less violent the 'hit' on a bump and the less bump steer it reacts to. The more positive it is the more it wants to stay straight. Which is fine until you wish to change direction. Feel! 1 to 2 degrees is plenty and keeps the steering light and responsive and the 'hit' light.  

 

Camber. Ditto. Drivers side more positive than the passenger side and since we are using negative camber more positive means less negative. Right? I like to be on the negative side when weigh bias is forward as is the case in most front engine configurations. In a pickup with a straight rear axle it's more important IMHO as a bit negative helps keep the nose from rolling the tire past neutral in most normal driving. Positive camber is more of a luxo boat float. 

 

Those two together keep the drivers side tire from 'climbing' the roads natural 'crown'. Road is always higher in the center than the at the curbs. With this set up and electronic power steering natural 'dampener' so rolles straight down th road hands off the wheel and will nose into a turn without input. A second reason for negative camber. Keep it from getting to tight. Loose cars scare passengers. Tight cars scare drivers. No one likes the wall. 

 

A hair positive toe counters the negative camber wear tendency and keeps the shimmy at bay when you hit a bump. It is imperative that they are DEAD equal. 

 

All my road adjustments are darn near neutral which limits 'drag' thus the crazy rolling distance and economy enhancement. 

 

I strive for zero thrust angle and zero steer ahead. Under 1/10 degree is hard to notice from the rear and hard for the driver to sense in the seat. I settled on zero steer ahead and 0.04 thrust. 

 

Hope that is helpful. BTW notice scralatchtica824 alignment sheet. The factory target values reflect my specs as to differences between left and right sides. 

 

Many shops with a machine do not care if it is right. Only that it is IN spec. And that no matter how much they charge. this is where the personal relationship with a guy who KNOWS HOW is handy  

What are you thoughts on my alignment sheet with the significantly out of spec thrust angle?