Any tips to improve fuel mileage?

[2kwik4u]

17 minutes ago, Grumpy Bear said:

..........

 

A word on fuel. Think in terms of cost per mile instead of MPG when making that choice. 87 is fine. Your truck as a KR sensor.  .......

 

 

I want to take a second and elaborate on this portion of the EXCELLENT post above.

 

I do the following for every vehicle I've owned since my '00 S10 (like 7 of them now I think)......Drive for a month on each of the fuels your vehicle can accept. For instance, I had a '12 Focus Se. It would accept 87, 89, 93, and E85. After driving each fuel for a month I computed the dollars spent per mile driven for each fuel. Turns our 87 octane was the MOST expensive fuel I could be using. Followed by 89, E85, and 93. The E85 and the 93 were within fractions of a cent of each other ($0.115 and $0.118 per mile). This was based on a the cost of E85 being around $2/gal, and 93 around $3.75/gal. In the end, I ran 93 in that car with great results.

 

I'm in the process of testing my current truck. Been running 93 Octane for almost a full month now after trying 87, and 89. So far the results are far less dramatic than with other cars. Each fuel is netting me REALLY close to $0.175/mi. 87 was $0.172/mi and 93 is currently at $0.178/mi. The 93 however runs SIGNIFICANTLY smoother in a subjective "feel" assessment. I'm most likely going to continue with the 93 when I complete the test based on that feel alone. Considering the price is so near the same on a per mile basis.

 

The assumption here is that the factory tune was running with some level of knock retard on the 87 at all times. With the 93 it is allowing itself to "trim" the timing higher, make a few more hp, and offset the added cost of the premium fuel. Obviously it's on the order of fractions of a HP considering the relative cost per mile is SOOOO close. 

 

Moral of the story....don't just say 87 is the cheapest and let it be. There is a decent chance a higher octane/blend will be less expensive, and (at least in my particular case), it might be a wash in terms of cost, but a win in terms of driving feel. Data is your friend, and follow it's trends more than any placebo effect you might get.

Edited May 29, 2019 by 2kwik4u

[Sierra Dan]

Marty is good, Marty is Wise

[xSHIFTxNASTYx]

16 minutes ago, 2kwik4u said:

...... Moral of the story....don't just say 87 is the cheapest and let it be. There is a decent chance a higher octane/blend will be less expensive, and (at least in my particular case), it might be a wash in terms of cost, but a win in terms of driving feel. Data is your friend, and follow it's trends more than any placebo effect you might get.

Fantastic post and thank you so much for sharing.  I really should go ahead and give this a go.  Are you waiting a certain amount of time before starting your data collection after switching octanes?  Before testing 89 I ran my tank as low as I could, filled it up completely, emptied it again and filled it up once more before beginning to analyze the difference with 89.  I ought to go back to 87 and start this all over again knowing that I'd probably end up at 93 considering that's what my Charger preferred.

Edited May 29, 2019 by xSHIFTxNASTYx

[2kwik4u]

1 minute ago, xSHIFTxNASTYx said:

Fantastic post and thank you so much for sharing.  I really should go ahead and give this a go.  Are you waiting a certain amount of time before starting your data collection after switching octanes?  Before testing 89 I ran my tank as low as I could, filled it up completely, emptied it again and filled it up once more before beginning to analyze the difference with 89.  I ought to go back to 87 and start this all over again knowing that I'd probably end up at 93 considering that's what my Charger preferred.

I've always tried to start this in the spring time, right when it warms up and the providers have moved to summer blend.

 

I'll do basically the procedure you mention. Run it pretty dry, swap to next octane on the list, run a tank, and refill. Then start data collection.

 

This is the first vehicle I've had that didn't show a marked difference in $/mi. Even my '03 Yukon had a difference of $0.015/mi. While these are still just pennies per mile differences. Over the course of a 100,000 miles, that's $1,500 in fuel. Might be negligible to some, but seems worthwhile to me. I should also mention I've had a few vehicles where the choice was made for me (Audi A4 with mild tune, and Silverado SS with a rebuilt engine) to run 93. I've also found the opposite to be true where 87 has been the least expensive, for instance, wifes '10 Traverse also gave zero craps about octane, always returned nearly the same cost per mile, and had no noticeable driving benefits to one fuel or the other. We ran 87 in that one.

[Loco-diablo]

I've been running 89 octane in my 2017 5.3 midnight DC since day one.. On summer blend (now) I average about 20.5 mpg (75% hgwy/25% city). Average highway speeds are 75 mph.. It gets to about 18.5-19 mpg in the winter.  10% ethanol here in MA.. I've also tried 93 octane and didn't notice a difference in mpg vs 89

Edited May 29, 2019 by Loco-diablo

[Jacoby]

2 hours ago, Racindave said:

What’s the negative with Blackbear? Was thinking about a tune... wanna make sure it’s not a waste. 

The negative reviews speak for themselves.  If you got an 8 speed and want a trans tune theyre one of your only options.

 

If you have a 6 speed or don't want to tune your 8 speed then I highly recommend Diablew. 

[xSHIFTxNASTYx]

38 minutes ago, Loco-diablo said:

I've been running 89 octane in my 2017 5.3 midnight DC since day one.. On summer blend (now) I average about 20.5 mpg (75% hgwy/25% city). Average highway speeds are 75 mph.. It gets to about 18.5-19 mpg in the winter.  10% ethanol here in MA.. I've also tried 93 octane and didn't notice a difference in mpg vs 89

Thanks.  We basically have the same exact truck. 

 

Your numbers are pretty close to what I've seen so I feel a little better.  I probably got a tank of winter blend so that may be why I saw such a drastic dip all of a sudden... I'll have to keep an eye on it but I planned on running 89 anyway.

 

I also plan to go back and do a pen-and-paper method of calculating MPG vs $/mi as suggested by others in this thread.  It's a really good idea and has sparked my interest in looking at it at that level.

[bartonjude]

It costs to be sexy.

[xSHIFTxNASTYx]

7 minutes ago, bartonjude said:

It costs to be sexy.

AMEN

[scott.moody.9401]

I can't envision any scenario where higher octane nets better mpg, except at WOT. Yes, our trucks have high compression, knock sensors and timing retard when detonation is sensed. But at light throttle openings and enigne load, they should not come into play. Higher octane, and thus detonation resistance, mean that higher octane fuels burn more slowly; the flame propogation front is slowed down. With lower octane fuels, the combustion process is slightly faster, which is effectively the same as advancing timing, which always helps mpg (unless its advanced too far).

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[ksiesel]

36 minutes ago, scott.moody.9401 said:

I can't envision any scenario where higher octane nets better mpg, except at WOT. Yes, our trucks have high compression, knock sensors and timing retard when detonation is sensed. But at light throttle openings and enigne load, they should not come into play. Higher octane, and thus detonation resistance, mean that higher octane fuels burn more slowly; the flame propogation front is slowed down. With lower octane fuels, the combustion process is slightly faster, which is effectively the same as advancing timing, which always helps mpg (unless its advanced too far).

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You have to remember that while in V4 mode, you are essentially simulating high load - just on those 4 cylinders instead of all 8.  This is really the reason that there is an efficiency gain in V4 as it allows the throttle plate to be much more open so your engine is able to breathe much more efficiently with only 4 cylinders pulling air past the throttle plate.

 

I've noticed that on 87, the 5.3 will go into a 5-7 degree timing Knock Retard just before the V4 mode shifts back to V8 mode.  As the KR is increased, it has to result in less power to the wheels.  As a result, this is a scenario where if the KR was not present it would operate in V4 longer before having to shift to V8.  During that time period, I suspect that efficiency would be improved.

 

I've not run anything other than 87 in my 5.3 yet to test, but this is what I'm seeing in the baseline data that I'm logging on my truck now.

[2kwik4u]

57 minutes ago, scott.moody.9401 said:

............ With lower octane fuels, the combustion process is slightly faster, which is effectively the same as advancing timing, which always helps mpg (unless its advanced too far).

 

I think this is hte exact case. I've been watching the data on timing and knock retard on my truck for a few weeks. I don't have good longs to backup my anecdotal thoughts here.....HOWEVER.....it appears that running on 93 nets me less overall time with knock retard in effect. Leading me to believe the timing parameters are setup such that they are purposefully advanced, and letting the knock sensor report problems and adjust on the fly. This would lead to a "constantly optimized" condition where the truck was always running as much timing as practical, without undue risk of damage. SO.....When moving to 93, you spend less time with timing retarded and see a net overall gain.

 

Again, though, the gain is small. Very small. Just enough to offset the difference in the cost of the fuel on a per mile basis it appears. Defintiely not enough to feel in the seat of the pants, or hear in the ping of the engine.

[Cpl_Punishment]

If you live in a hilly area, cruise control is not your friend. I found that switching from a mentality of trying to maintain speed on my commute to trying to maintain throttle position and letting the speed drop when going uphill improved my mileage by ~50% (went from 20 mpg to 30 on my car).

[Doublebase]

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

 

I think tires/rim combination makes a big difference. I have the 17's with the Bridgestones that came with the truck, I'm not thrilled with the way they look but they do seem to help in the fuel economy department. 

 

I can easliy get this truck into V4 mode by simply getting it up to speed and backing off if the throttle a little bit. Boom, it goes right into V4 and will stay there until I need to accelerate or go up a hill...then I go back into V4. Highway I just set the Cruz at 68 and keep it there unless I need to pass someone or step on the brake (it generally stays in V4 probably 60 percent of the time). 

 

I found that intitially I was kind of able to "train myself" by leaving the fuel mileage screen up on the dash to kind of gauge how I was driving and what I was able to accomplish.

 

I'm almost averaging better fuel economy in my V8 4WD truck than my wife is in her 4cyl Honda CRV (pretty damn close).

[Grinnen]

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