Any tips to improve fuel mileage?

ammoaddict · May 30, 2019

Nobody ever understands what Octane does.

The higher the octane the higher the ignition temperature. Some vehicles, mainly older ones, require a higher octane due to pre-ignition because of how engine heat is concentrated in areas, or to stop it from igniting in the cylinder (again, because of heat) before the spark sets it off. That's it, that's all. Nothing magic about a higher octane unless you've changed your engine/ignition system in a significant way that makes it require a higher octane.

Proper truck geometry will net the highest gains. When they are tested in the wind tunnel and configured for aerodynamics they are flat, as in no tires and held on a lift/table. When they are sold they have that rake added because of the suspension which is meant to carry heavy loads in the rear. Just installing a level kit added almost 1km/liter to my mileage. I've been tracking it for a long time via fill ups, the trucks trip recordings and calculations.

I went from 12.4L/100km to 11.6L/100km (22-23MPG to 25-26MPG). You can call me out on this if you desire, but I don't care. I'm passing along my experience.

- A tonneau cover will help mileage on the factory suspension because it covers the open bed which destroys any aerodynamics when the trucks ass is in the air. When level it doesn't do a lot.

- Alignment : if they aren't tracking properly this can really affect mileage

- Tires : Not a larger tire but more the tread pattern will affect MPG. I went on my older vehicle (AMC Eagle with full Jeep drivetrain swap) from a street tire to a luggy as hell AT tire and lost about 1/5 of my mileage. But meh.

- Accessories : Ever see those ugly ass fender flares that some places sell that stick out 3-4" to cover the tire? Morons with huge spoilers on their Cavaliers and Sunfires that only work if you're capable of 170 miles an hour? Yeah..may as well add a parachute to the rear.

- Lift kits : they can affect mileage but only because of the larger disproportionate tires needing more horsies to turn and causing a bit of wind resistance. The lift in itself leaves vehicle geometry the same. However if the vehicle was designed to squat at higher speeds a lift kit will ruin it...but that's not what a pickup was designed for.

- Vehicles learn how a person drives and over time will adapt to this for the best MPG. If you swap drivers this can affect it initially but over time it will adapt.

In the end your driving a 5000 pound 6' tall brick, with great capability and usefulness. You'll never achieve amazing mileage

I understand what octane is. Running higher octane than what your engine is designed for does absolutely nothing to improve fuel economy or increase horsepower in modern vehicles. It's a proven fact.

Sent from my Moto G (4) using Tapatalk

2kwik4u · May 30, 2019

1 hour ago, ammoaddict said:

I understand what octane is. Running higher octane than what your engine is designed for does absolutely nothing to improve fuel economy or increase horsepower in modern vehicles. It's a proven fact.

Sent from my Moto G (4) using Tapatalk

The problem with these types of statements is that most people don't understand modern engine control systems. More often than not there are advanced sensing algorithms, and active feedback control loops that can and will allow advanced ignition timing settings. So simply saying "Higher octane doesn't do anything" is incorrect. Even adding "than what your engine was designed for" isn't really correct, since it was designed to run on ALL fuels not just ONE fuel. Without intimate knowledge of the control system, the only way to tell if a higher octane fuel will improve the situation is by experimentation.

My '12 Focus reacted quickly and significantly. My wifes '10 Traverse had no reaction at all. My Sierra has a subtle reaction.

aseibel · May 30, 2019

20 hours ago, Doublebase said:

My lifetime average in my 2018 5.3 is 24.2 - now it'd be better if I didn't have to drive 5 months out of the year in temps under 40 degrees....once it gets over 40 degrees my mileage improves dramatically. Winter I average 23, summer I average 25.6

It's not the temperature affecting your mileage, it's the winter blend gas.

"The US Environmental Protection Agency (EPA) says conventional summer-blend gasoline contains 1.7 percent more energy than winter-blend gas, which is one reason why gas mileage is slightly better in the summer."

https://newsroom.aaa.com/2013/06/what-is-the-difference-between-summer-and-winter-blend-gasoline/

Doublebase · May 30, 2019

1 hour ago, aseibel said:

It's not the temperature affecting your mileage, it's the winter blend gas.

"The US Environmental Protection Agency (EPA) says conventional summer-blend gasoline contains 1.7 percent more energy than winter-blend gas, which is one reason why gas mileage is slightly better in the summer."

https://newsroom.aaa.com/2013/06/what-is-the-difference-between-summer-and-winter-blend-gasoline/

Understood, but air density plays a roll in fuel economy...cold air=more dense. The computer adjust fuel ratios to meet stoichiometric 14.7 to 1 air fuel mixtures...the colder the air, the more dense, means more fuel. Mass air flow sensors, manifold absolute pressure sensors and intake air temperature sensors are easily able to determine air density and temperature.

On the same tank of gas, winter blend or not, I will receive better fuel economy when the temps go above 40 degrees.

Also on cold morning starts the computer will demand the fuel injectors to pulse width rich until parameters are met (engine temp, closed loop, O2 sensor feedback, etc).

Edited May 30, 2019 by Doublebase

aseibel · May 31, 2019

14 hours ago, Doublebase said:

Understood, but air density plays a roll in fuel economy...cold air=more dense. The computer adjust fuel ratios to meet stoichiometric 14.7 to 1 air fuel mixtures...the colder the air, the more dense, means more fuel. Mass air flow sensors, manifold absolute pressure sensors and intake air temperature sensors are easily able to determine air density and temperature.

On the same tank of gas, winter blend or not, I will receive better fuel economy when the temps go above 40 degrees.

Also on cold morning starts the computer will demand the fuel injectors to pulse width rich until parameters are met (engine temp, closed loop, O2 sensor feedback, etc).

At first I was going to offer to sell you a warm air intake. But then I thought about what you are saying. I don't know how much more fuel is actually used per engine cycle at 20 degrees vs 80 degrees. But I do know that colder, denser air = more compression = more power. So your engine may be burning more fuel per cycle, but its also creating more power, so I think that kind of balances out. You may be able to achieve the same speed with slightly less throttle in the cold.

If you're going to blame poor economy on the air temp, don't forget that your cold, dense air is also creating more wind resistance & drag than warm, less dense air.

At the end of the day, you just have to drive in whatever conditions you live in. Nothing you do to your truck is going to change that. The whole point of this thread is what can you do to maximize the fuel efficiency of a brick. I guess you have determined the answer is move farther south.

xSHIFTxNASTYx · May 31, 2019

Thank you all for your feedback. This has been a great discussion. A lot of great back-and-forth going on. I’m glad to be here and reading all of this.

Grumpy Bear · May 31, 2019

1 hour ago, aseibel said:

At first I was going to offer to sell you a warm air intake. But then I thought about what you are saying. I don't know how much more fuel is actually used per engine cycle at 20 degrees vs 80 degrees. But I do know that colder, denser air = more compression = more power. So your engine may be burning more fuel per cycle, but its also creating more power, so I think that kind of balances out. You may be able to achieve the same speed with slightly less throttle in the cold.

If you're going to blame poor economy on the air temp, don't forget that your cold, dense air is also creating more wind resistance & drag than warm, less dense air.

At the end of the day, you just have to drive in whatever conditions you live in. Nothing you do to your truck is going to change that. The whole point of this thread is what can you do to maximize the fuel efficiency of a brick. I guess you have determined the answer is move farther south.

You hit the nail on the head Andy. An engine is a 'demand' device. It makes exactly the amount of power required to overcome whatever resistance is against it. If it has the ability to make more power than is nice but if it is against a 25 hp. load it makes ONLY the 25 hp. needed. The power the motor makes is in the fuel, not the air. If it were only about air (O2) then a Nitrous motor should make about a million mpg. Hit the spray bar and voila, mpg.

To Doublebase's point a less restricted inlet that allows more air would also mean a lower throttle angle and thus higher pumping losses leading to lower mpg. If there is any change at all it will be due to the air fuel mapping. For the same rpm the MAP will be altered which may alter the fuel delivery RATIO (maybe). IF that leans the mix a bit the blade will open more, the pumping losses decrease the mpg MAY go up. If it's too lean it may go down. The power comes from the exact mix of energy release delivered by a specific ratio of air/fuel. That has to do with turbulence, and....and....and....and

You guys get the point, right? It's complicated. Thing to remember is correlation is not causation. Marketing people make a living out of such happen stance without ever knowing why and if they do....they lie from the heart. Keeps the natives ignorant and easy to manipulate.

In the days of the carburetor if you wanted great mpg form a certain set up you used a vacuum gauge and drove to the highest vacuum. Today with GDI they attempt to deliver the highest MAP which is opposite high vacuum. Back in the day the higher the vacuum the lower the fuels boiling point the greater amount of liquid was turned to vapor the more BTU was available to be put to work. That job has been turned over to events AFTER the intake manifold. A .04 second blast of high pressure fuel delivered from a very precise spray patterned nozzle in a cylinder rapidly descending does that trick.

In effect you two are both right, right? C'mon man...smile!

BTW the comment on winter air being denser thus harder to push a truck through? True! But hard to measure on anything other than a slide rule.

Doublebase · May 31, 2019

2 hours ago, aseibel said:

At first I was going to offer to sell you a warm air intake. But then I thought about what you are saying. I don't know how much more fuel is actually used per engine cycle at 20 degrees vs 80 degrees. But I do know that colder, denser air = more compression = more power. So your engine may be burning more fuel per cycle, but its also creating more power, so I think that kind of balances out. You may be able to achieve the same speed with slightly less throttle in the cold.

If you're going to blame poor economy on the air temp, don't forget that your cold, dense air is also creating more wind resistance & drag than warm, less dense air.

At the end of the day, you just have to drive in whatever conditions you live in. Nothing you do to your truck is going to change that. The whole point of this thread is what can you do to maximize the fuel efficiency of a brick. I guess you have determined the answer is move farther south.

Good points I'll also add...alternator and lower battery voltage due to the cold. It will affect fuel economy when the alternator puts a drag on the engine to charge the battery. Another thing is heated seats and steering wheel...those two things I found to be factors. Cold starts and rich fuel mixtures, tire pressures...on and on. So many factors.

It is interesting, and you're right, winter fuel is also one of those factors to consider.

16LT4 · May 31, 2019

The time of day you fill up can also drastically effect your mileage. Fill up with 20 gallons at 6 am, and you might find it took much more fuel than 20 gallons than that afternoon at 2 pm. 20 gallons only equals 20 gallons if the temperature of those gallons is the same; on a recent trip in my Jetta, which usually obtains 31 mpg in summer and 29 mpg in winter over my 400 mile round-trip commute for work each weekend, I scored an unheard of 38 mpg. After the next fill-up, I was down to 25. Why? I put fuel in the tank at the beginning of the first trip at 52* F, and filled up again that afternoon at 80*F. The fuel expanded, giving the illusion of greater efficiency. This is why many tanks over many weather cycles should be averaged for accuracy. On a side note, on average (though short thus far), my "new to me" '16 Silverado CC is only 7% more per mile than my Jetta over that work commute, using E85. Using my nearly-similar '17 Silverado which ran only 87 as a comparative measure, as I've only run E85 in the '16 and have zero data for other fuels, it was substantially more at 32% more per mile. So far, I see no reason to switch, as I know what I got in the '17, and I've only lost <2 mpg on the '16; time will tell if that gap wides as less and less residual 87 remains in the tank (I never let it get less than 1/4 tank before refueling).

While I completely agree with Grumpy's description above regarding optimum stoich ratios, the variable not mentioned is the Simian behind the wheel, who more often than not requires more power than the engine does, hence efficiency declining. Unless the 5.3 programming is different, no engine I've ever come across adjusts the amount of air entering the engine to meet a predetermined fuel map, but rather adjusts the fuel map to meet the air coming in (hence IAT sensors, MAP/MAF sensors, O2 sensors, etc). The driver is used to pushing foot down X amount and opening throttle plate that amount, and often does so without feeling slightly more power in colder air. The best track times are posted in late fall when the air is crisp and DRY (let us not also forget that humid air has less O2 per mole than dry air, but is also lighter), when the engines make the most power despite the slight increase in resistance. The biggest issue for decreased economy on winter fuels, while being a combination of factors, is likely warming the vehicle up before driving coupled with the engine spending much more time in open loop mode running rich (choked, in the carb days... I won't say "old," as 2 of my daily drivers are carbed). My F-150 would take an extra 5 miles to reach operating temperature in January vs. June on my same commute to work everyday with the same country traffic (or lack thereof), and even an extra 30 seconds of warm-up adds up. Warming up a vehicle nets you 0mpg, and 0s lower the average quickly.

The single biggest thing you can do to maximize fuel economy is to modify the aforementioned Simian.

Grumpy Bear · May 31, 2019

36 minutes ago, dukedkt442 said:

While I completely agree with Grumpy's description above regarding optimum stoich ratios, the variable not mentioned is the Simian behind the wheel, who more often than not requires more power than the engine does, hence efficiency declining.

While I did mention it in an earlier posting to this thread I have to say I do love your wording.

16LT4 · May 31, 2019

1 hour ago, Grumpy Bear said:

While I did mention it in an earlier posting to this thread I have to say I do love your wording.

Was it you who mentioned the nut behind the wheel? Also a great description. I do recall that and obviously agree; my mentioning again was more towards the specificity of a greater air charge decreasing economy despite increased power and the theoretical work performed being the same. This Simian, for one, isn’t nearly that precisely calibrated.

Ravenkeeper · June 1, 2019

Contrary to popular belief, in this case mis-belief, an open bed with tailgate up gets the best MPG. But, I'm still going to install a tonneau cover in the near future. I still check my tire pressures once a month (usually on/around the 1st), religiously use my cruise control (even when transitioning to different speeds between 24MPH-65MPH), and don't drive any faster than 65MPH.

Mythbusters (tailgate up vs down)

http://www.discovery.com/tv-shows/mythbusters/mythbusters-database/driving-tailgate-fuel-consumption/

https://removeandreplace.com/2015/07/28/does-a-pickup-truck-get-better-gas-mileage-with-the-tailgate-up-or-down/

Tailgate UP vs DOWN vs Tonneau Cover:

https://www.consumerreports.org/cro/news/2013/08/pickup-truck-tailgates-and-fuel-economy/index.htm

Edited June 1, 2019 by Ravenkeeper

Grumpy Bear · June 1, 2019

Anyone ever see a cup truck running with an open bed? Drag reduction is kind of a big dill. If they ran faster with more drag they would run open and 90 degree Gurney wings.

https://www.google.com/search?q=NASCAR+Trucks&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjW66fhrsfiAhVGRK0KHSDFCmoQ_AUIESgC&biw=1344&bih=721

Somewhere I ran across a major university study on this topic with tunnel test. Soft bed cover works. I hit 30 mpg at 60 mph with the cover. If I thought for a second that taking it off would improve mileage it would be gone on a New York second.

garagerog · June 1, 2019

I'm not getting into the cover vs. non-cover mpg argument, but Grumpy using one of the Gander Series Nascar trucks is probably not a good example. I believe if you pull that cover back, you're not going to see an actual truck bed, but chassis rails, a driveshaft, trailing roll-bar as part of the cage, a fuel cell, plus a lot of asphalt. Even if they had a truck bed in them, they would still use a cover to direct air on the rear spoiler for down-force, which is more for handling than absolute top speed at tracks other than Daytona or Dega.