Solving the MPG Dilemma

[Marztian]

First off, I'll start by saying I know the MPG issue has always been beat to death. I'll also say that every conversation seems to lead to almost no real solution, rather people talking about how trucks don't get great MPG or maybe how someone should have a lighter foot or remove their leveling kit and heavier wheels. Now comes my situation (and I think that of others in the same boat).

 

I have a 2018 Crew Cab Short Bed Silverado LT Z71 - 5.3L 6spd with the 3.42 gearing, right arounf 47,000 miles. Aside from bone stock, I have a cab-height topper and stock sized BFG KO2s. No lift/level, OEM exhaust, and OEM intake with a K/N performance filter.

 

MPG used to be ~18 avg - right along with what one would expect and what most people get. Since last Fall (September 2019), I've been getting 12-13 city and 14-15 highway. I've also started logging all fuelups into fuelly for tracking. One point also worth noting: I drive like a grandpa: slow-moderate acceleration, try to stay in the 55-65 window as much as possible, and only go about 73 on the interstate. No matter what, the MPG still sucks. This is with minimal remote starts and idle time, using 55mph county roads instead of city/stoplights, etc.

 

The purpose of this is to try to find a SOLUTION, or at least get pointed in the right direction for one. Many pages discuss MPG being low, but not WHY or HOW and that insight is what's most important.

 

And another note: I didn't buy a truck to get 22 mpg. But, when your tank is 26 gallons and it should be putting you 450 miles, 350 is kind of a slap in the face. Simply put: it shouldn't be this way, so how can it be fixed. Any insight or personal experiences would be great. Only probable solution so far has been valve coking. This truck has almost all highway miles on it and I'm looking into Blackbear tuning, but I don't think that will be solving any underlying issues.

[Grumpy Bear]

Noted is the mileage loss occurred during the winter months. You don't say where you live but where I live this is quite normal and expected. This is a multiyear chart of my truck. Troughs are winter, peaks are summer. BIG difference.

 

 

 

. 

 

A tool I've used to help is the Scan Gauge II which plugs into the OBD-2 port and allows you to watch in real time, short term, daily and tank averages. Plus a zillion other related things and more.There is a piggyback available with real time charting. When you can see what's happening it changes the your habits. It even changed the routes I take. Okay enough of that. 

 

IF your truck is in a good state of tune it becomes simple. Fuel is load and anything that reduces load saves fuel. Alignment in my case netted 3 mpg! Tire pressure changes with temperature. A good gauge and frequent checks netted another mpg. HT tires over AT tires is a nice bump. 

 

There's bunches more but....hope this helps. 

 

[newdude]

1 hour ago, Marztian said:

First off, I'll start by saying I know the MPG issue has always been beat to death. I'll also say that every conversation seems to lead to almost no real solution, rather people talking about how trucks don't get great MPG or maybe how someone should have a lighter foot or remove their leveling kit and heavier wheels. Now comes my situation (and I think that of others in the same boat).

 

I have a 2018 Crew Cab Short Bed Silverado LT Z71 - 5.3L 6spd with the 3.42 gearing, right arounf 47,000 miles. Aside from bone stock, I have a cab-height topper and stock sized BFG KO2s. No lift/level, OEM exhaust, and OEM intake with a K/N performance filter.

 

MPG used to be ~18 avg - right along with what one would expect and what most people get. Since last Fall (September 2019), I've been getting 12-13 city and 14-15 highway. I've also started logging all fuelups into fuelly for tracking. One point also worth noting: I drive like a grandpa: slow-moderate acceleration, try to stay in the 55-65 window as much as possible, and only go about 73 on the interstate. No matter what, the MPG still sucks. This is with minimal remote starts and idle time, using 55mph county roads instead of city/stoplights, etc.

 

The purpose of this is to try to find a SOLUTION, or at least get pointed in the right direction for one. Many pages discuss MPG being low, but not WHY or HOW and that insight is what's most important.

 

And another note: I didn't buy a truck to get 22 mpg. But, when your tank is 26 gallons and it should be putting you 450 miles, 350 is kind of a slap in the face. Simply put: it shouldn't be this way, so how can it be fixed. Any insight or personal experiences would be great. Only probable solution so far has been valve coking. This truck has almost all highway miles on it and I'm looking into Blackbear tuning, but I don't think that will be solving any underlying issues.

 

 

When did you purchase the truck/How long have you had it?  September/October is when winter blend fuels start to show their face if you are somewhere where they are used.  Right now winter blend is still what you will find in the pumps most likely due to the OPEC/COVID issues going on right now.  High supply of winter blend fuels that are stored waiting to be delivered, nobody driving to use it.  GM even acknowledged this as well.  Could winter blend be a concern?  Sure.

 

I have a 2019 LD (same body style as you) 5.3/3.42/A6 but a double cab standard box (same wheelbase as you).  My lifetime MPG in 15931 miles is 16.3mpg.  Corsa cat back, GM cold air and Range AFM disabler.  Intake was just added last month, the Range and the Corsa were on about a month after I bought it.  I warm it up in the winter, moderately accelerate to cruising speeds on highway.  Per tank, usually i'm in the 13-15mpg winter average, 17-18mpg summer average.  

 

My trip to work is 16 miles one direction, 2/3rds of it is on a 55mph road with traffic lights every 1-2 miles.  I usually am between 55-80mph on highway.  Truck sees plenty of WOT too. 

 

Currently on 93 octane for the last month, no tunes.  Stock size 265/65R18 tires for summer in General Grabber APT (all terrain tire) and winter is the tires the truck came with 265/65R18 Goodyear Wrangler Duratrac.  Both tire sets are run at the 38psi cold pressure per the door jamb.        

[Grumpy Bear]

A word on winter gas. BTU content is under 2% different. I made this stuff for years and seen thousands of labs on it. 2% is the maximum difference possible due to gas seasonal changes alone. Fuel is highly regulated and chemically defined. 

 

The killer in the winter isn't fuel. It is oil cold viscosity. Note on a hot day, 40 C 104 F. About 62 cSt (density adjusted) Now compare to a moderately cold day of 0 C or 32 F... Yea, almost 600 or ten times more viscous. Imagine what it is on a -40 C/F day. On a warm summer day it takes my truck perhaps 5 miles to reach full oil temperature. At freezing it takes up to 20 miles. 

 

 

This Pressure vs Load chart is actually for the Bridgestone Dueler HT 684 II 255/70R17

(Yes the General Grabber equivalent, the other OEM, has the same pressure profile).

 

Door Plate pressure is 35 psi meaning the door plate is for the maximum loaded condition.

 

It also happens to be the best mpg pressure in my situation. Ride however can be improved a bunch by using a pressure that reflects a more moderate value. I can tell you that at 118,000 miles on my original tires that the two outer ribs are only lately touching the road. There is 5/32 tread left. It's a very narrow footprint at 35 psi.This tire does not get calk flat until around 25 psi.

 

That pressure will also consume around 5-8% more fuel. 

 

 

 

[Marztian]

5 hours ago, Grumpy Bear said:

Noted is the mileage loss occurred during the winter months. You don't say where you live but where I live this is quite normal and expected. This is a multiyear chart of my truck. Troughs are winter, peaks are summer. BIG difference.

 

 

 

. 

 

A tool I've used to help is the Scan Gauge II which plugs into the OBD-2 port and allows you to watch in real time, short term, daily and tank averages. Plus a zillion other related things and more.There is a piggyback available with real time charting. When you can see what's happening it changes the your habits. It even changed the routes I take. Okay enough of that. 

 

IF your truck is in a good state of tune it becomes simple. Fuel is load and anything that reduces load saves fuel. Alignment in my case netted 3 mpg! Tire pressure changes with temperature. A good gauge and frequent checks netted another mpg. HT tires over AT tires is a nice bump. 

 

There's bunches more but....hope this helps. 

 

 I realize that the AT KO2s (especially as aggressive as they are) will net lower mpg- but, I keep them at ~39-41 psi at any given time. I could also see the weight/aerodynamics of the topper reducing mpg. But these aside, the frustration is that it ISNT what it should be or has been. I know the truck is capable of 17-18mpg (as it used to be) especially how I drive it, but I’m not getting what I believe I should (and I think that’s a justified statement). I do appreciate your acknowledgement of other variables, but I’ve tried to minimize many of those already. Actually, much insight has come from reading YOUR posts on other threads! I’m really trying to find where to go next, as I think something is mechanically or digitally wrong. Coked intake valves? Catalytic converters acting up? I do use 87 unleaded and actually just started using 88 unleaded (E15) to see of any tangible difference. I would be down to run a test on 91 no ethanol (no 93 around here), but haven’t yet.

 

As for a winter reference- I don’t believe that’s it... sure I could be wrong, but I’ve never seen a difference like this that could be relatable. Even then, should be better than 12-13mpg. I live in central IL so I’m sure winter fuel may still be out.

[CamGTP]

For the hell of it, check your air filter and clean the MAF sensor with MAF cleaner.

 

Hook up a scan tool if you are handy and know what you to for, things can be watched to see if something is looking odd like fuel trim data.

[Marztian]

5 hours ago, newdude said:

 

When did you purchase the truck/How long have you had it?  September/October is when winter blend fuels start to show their face if you are somewhere where they are used.  Right now winter blend is still what you will find in the pumps most likely due to the OPEC/COVID issues going on right now.  High supply of winter blend fuels that are stored waiting to be delivered, nobody driving to use it.  GM even acknowledged this as well.  Could winter blend be a concern?  Sure.

 

 

I have a 2019 LD (same body style as you) 5.3/3.42/A6 but a double cab standard box (same wheelbase as you).  My lifetime MPG in 15931 miles is 16.3mpg.  Corsa cat back, GM cold air and Range AFM disabler.  Intake was just added last month, the Range and the Corsa were on about a month after I bought it.  I warm it up in the winter, moderately accelerate to cruising speeds on highway.  Per tank, usually i'm in the 13-15mpg winter average, 17-18mpg summer average.  

 

My trip to work is 16 miles one direction, 2/3rds of it is on a 55mph road with traffic lights every 1-2 miles.  I usually am between 55-80mph on highway.  Truck sees plenty of WOT too. 

 

Currently on 93 octane for the last month, no tunes.  Stock size 265/65R18 tires for summer in General Grabber APT (all terrain tire) and winter is the tires the truck came with 265/65R18 Goodyear Wrangler Duratrac.  Both tire sets are run at the 38psi cold pressure per the door jamb.        

Good insight. I’ve only owned the truck since March (the last 2000 miles), but a good buddy of mine bought it new at the end of 2018, and I’ve seen the hand-calculated mpg numbers since that time as to what his mpg was. He’s a lead foot and tows boats a lot and still averaged more than me in all circumstances, winter included. I’ve been trying to build up the best base I could, but time is in high demand as I move closer to a BBP time, intake, and muffler delete. But, I’d like hard numbers off the stock configuration so I’m then able to correct any problems before moving on to mods. Catch can is ready to be installed too- so if coked valves is it, I’d like them cleaned out and then a bottle of crc run through here and there after the catch can.

[Grumpy Bear]

2 minutes ago, Marztian said:

Good insight. I’ve only owned the truck since March (the last 2000 miles), but a good buddy of mine bought it new at the end of 2018, and I’ve seen the hand-calculated mpg numbers since that time as to what his mpg was. He’s a lead foot and tows boats a lot and still averaged more than me in all circumstances, winter included. I’ve been trying to build up the best base I could, but time is in high demand as I move closer to a BBP time, intake, and muffler delete. But, I’d like hard numbers off the stock configuration so I’m then able to correct any problems before moving on to mods. Catch can is ready to be installed too- so if coked valves is it, I’d like them cleaned out and then a bottle of crc run through here and there after the catch can.

This is useful! Averages that can be relied on happen over tens of thousands of miles not single tanks nor even the average of a few. That chart took four years tracking every tank. The kind of data your after, and rightly so, would take a least a season or so. Different driver. Different situation. Catch a glimpse of a tank now and again....I wonder....tell ya what....

 

Set your own bar. Start fresh and take Cameron's advice. He good with stuff like this. 

 

Anyway that's all the damage I can handle   Wish you success. 

[Marztian]

19 minutes ago, CamGTP said:

For the hell of it, check your air filter and clean the MAF sensor with MAF cleaner.

 

Hook up a scan tool if you are handy and know what you to for, things can be watched to see if something is looking odd like fuel trim data.

Air filter (the cleanable, reusable K&N) has been clear. One of the first things I did when I got the truck was clean it out, reverse blow it, and ensure it wasn’t sapped with filter oil. But I suppose one thing I’ve not done is make sure the MAF sensor wasn’t already doused in the oil. Will be cleaning that ASAP. Any specific brand/product you recommend as a cleaner?

 

As for scanning, not entirely handy on the ECM topic. I was looking at having a scan done as part of this process, but don’t know how exactly to go about it. Anything you recommend to do or a specific thing to ask of a mechanic?

 

Very appreciative of the help.

[Eddie 70]

I bought a small can of CRC MAF (red can) cleaner at Autozone or one of those parts stores. While I was at it, I also removed the throttle body and cleaned the carbon build up on it.

[UnlimitedMatt]

22 hours ago, Marztian said:

First off, I'll start by saying I know the MPG issue has always been beat to death. I'll also say that every conversation seems to lead to almost no real solution, rather people talking about how trucks don't get great MPG or maybe how someone should have a lighter foot or remove their leveling kit and heavier wheels. Now comes my situation (and I think that of others in the same boat).

 

I have a 2018 Crew Cab Short Bed Silverado LT Z71 - 5.3L 6spd with the 3.42 gearing, right arounf 47,000 miles. Aside from bone stock, I have a cab-height topper and stock sized BFG KO2s. No lift/level, OEM exhaust, and OEM intake with a K/N performance filter.

 

MPG used to be ~18 avg - right along with what one would expect and what most people get. Since last Fall (September 2019), I've been getting 12-13 city and 14-15 highway. I've also started logging all fuelups into fuelly for tracking. One point also worth noting: I drive like a grandpa: slow-moderate acceleration, try to stay in the 55-65 window as much as possible, and only go about 73 on the interstate. No matter what, the MPG still sucks. This is with minimal remote starts and idle time, using 55mph county roads instead of city/stoplights, etc.

 

The purpose of this is to try to find a SOLUTION, or at least get pointed in the right direction for one. Many pages discuss MPG being low, but not WHY or HOW and that insight is what's most important.

 

And another note: I didn't buy a truck to get 22 mpg. But, when your tank is 26 gallons and it should be putting you 450 miles, 350 is kind of a slap in the face. Simply put: it shouldn't be this way, so how can it be fixed. Any insight or personal experiences would be great. Only probable solution so far has been valve coking. This truck has almost all highway miles on it and I'm looking into Blackbear tuning, but I don't think that will be solving any underlying issues.

I have the same truck with 22000 miles but I do have a tune from Trifecta and a GM Performance cold air intake.  I do have a catch can & clean side separator.  I have done the transmission thermostat delete and added an auxiliary aft filter.  I also switched to 5w30 Mobil 1 oil.  My mileage sucks too!  My average is lower due to me towing my 7500 pound camper.  I am pretty sure my mileage went down last year when I installed my LT 275/65R18 load range E tires.  I do run 91 octane fuel to maximize the tune.  I have tracked my mileage with Fuelly since day one.

 

 

[Marztian]

3 hours ago, UnlimitedMatt said:

I have the same truck with 22000 miles but I do have a tune from Trifecta and a GM Performance cold air intake.  I do have a catch can & clean side separator.  I have done the transmission thermostat delete and added an auxiliary aft filter.  I also switched to 5w30 Mobil 1 oil.  My mileage sucks too!  My average is lower due to me towing my 7500 pound camper.  I am pretty sure my mileage went down last year when I installed my LT 275/65R18 load range E tires.  I do run 91 octane fuel to maximize the tune.  I have tracked my mileage with Fuelly since day one.

 

 

Interesting to see the difference with the Load Es. I can believe that they play a part of the drop, but especially in my case, with that being the only variable change, I really won’t believe it costs 4mpg. I’m going to spray my MAF sensor here soon and install the E2 catch can w/CSS. Maybe a difference, maybe not. Will probably get more invasive with an intake manifold and intake valve cleaning in a month or 2 when I’m closer to an oil change. I’d also like to buy a scope and scope my valves as well as my cats to see what shape they’re in. Such a fun time... 

 

Thanks for the help and any additional thoughts are appreciated! I’m guessing this will be an ongoing topic.

[Grumpy Bear]

2 hours ago, Marztian said:

Interesting to see the difference with the Load Es. I can believe that they play a part of the drop, but especially in my case, with that being the only variable change, I really won’t believe it costs 4mpg. I’m going to spray my MAF sensor here soon and install the E2 catch can w/CSS. Maybe a difference, maybe not. Will probably get more invasive with an intake manifold and intake valve cleaning in a month or 2 when I’m closer to an oil change. I’d also like to buy a scope and scope my valves as well as my cats to see what shape they’re in. Such a fun time... 

 

Thanks for the help and any additional thoughts are appreciated! I’m guessing this will be an ongoing topic.

Believe it. Factory fit is 265/65R18. The 275's add weight and weigh kills efficiency.

[Marztian]

52 minutes ago, Grumpy Bear said:

Believe it. Factory fit is 265/65R18. The 275's add weight and weigh kills efficiency.

Good point, I failed to see that he had the wider 275s the first time. I’m rolling on stock sized BFG KO2s which are

A) more aggressive and

B) weigh 54% more (33lb->51lb)

So, I get they are reducing efficiency some from stock.

They are amazing tires, but if the price is 4mpg..... other options may quickly become more viable! Wish and hope that isn’t the case.

[Grumpy Bear]

16 hours ago, Marztian said:

Good point, I failed to see that he had the wider 275s the first time. I’m rolling on stock sized BFG KO2s which are

A) more aggressive and

B) weigh 54% more (33lb->51lb)

So, I get they are reducing efficiency some from stock.

They are amazing tires, but if the price is 4mpg..... other options may quickly become more viable! Wish and hope that isn’t the case.

Yea that's huge. Up and down hills doesn't hurt much. Gravity helps regain the losses but from a stop 18 lbs a wheel is a boat anchor. It's hard on gas and it's hard on brakes. Brakes don't stop a vehicle. Brakes stop wheel/tires. They stop the truck. It's the difference between catching a soft ball tossed at you and an 20# medicine ball. Here, catch.