Poor gas mileage

[Tazithman]

I'm done with this exchange as a peeing contest is not beneficial to the board.

 

[ktl5005]

Last tank. 400 miles, 14.5mpg average per fueley. 3.21 Hemi MDS, Limited. Thay was about as good as my 2017 Trailhawk with Wrangler Duratracs

 

[skidmarc]

There very well may be truth to using heavier acceleration to get better fuel mileage, vs crawling up to speed. The key is brake specific fuel consumption and knowing where an engine is most efficient. I don't know what the chart looks like for the Hemi, but it can be proven that an engine might be less efficient at 1,500 rpm vs 2,500 for example. Because of that, it may be more economical to run the engine at 2,500 rpm for a shorter amount of time vs spending more time in a less-efficient RPM range. The hyper-miler folks with hybrids and what-not rely on this BSFC data for some of their fuel saving strategies.

See "Pulse and glide" and "Causes of pulse-and-glide energy saving", here: https://en.wikipedia.org/wiki/Energy-efficient_driving

 

[PowerJrod]

There very well may be truth to using heavier acceleration to get better fuel mileage, vs crawling up to speed. The key is brake specific fuel consumption and knowing where an engine is most efficient. I don't know what the chart looks like for the Hemi, but it can be proven that an engine might be less efficient at 1,500 rpm vs 2,500 for example. Because of that, it may be more economical to run the engine at 2,500 rpm for a shorter amount of time vs spending more time in a less-efficient RPM range. The hyper-miler folks with hybrids and what-not rely on this BSFC data for some of their fuel saving strategies.

See "Pulse and glide" and "Causes of pulse-and-glide energy saving", here: https://en.wikipedia.org/wiki/Energy-efficient_driving

Very true for Hybrid vehicles, smaller engines or diesel engines. I'm sure 2,000 - 2,500 RPMs in the Hemi for a SHORT distance to get up to speed is fine...like an on ramp to the highway or going uphill. That would make perfect sense.

 

[PowerJrod]

I'm done with this exchange as a peeing contest is not beneficial to the board.

Good idea! Happy gas pedal mashing!

 

[Tazithman]

There very well may be truth to using heavier acceleration to get better fuel mileage, vs crawling up to speed. The key is brake specific fuel consumption and knowing where an engine is most efficient. I don't know what the chart looks like for the Hemi, but it can be proven that an engine might be less efficient at 1,500 rpm vs 2,500 for example. Because of that, it may be more economical to run the engine at 2,500 rpm for a shorter amount of time vs spending more time in a less-efficient RPM range. The hyper-miler folks with hybrids and what-not rely on this BSFC data for some of their fuel saving strategies.

See "Pulse and glide" and "Causes of pulse-and-glide energy saving", here: https://en.wikipedia.org/wiki/Energy-efficient_driving

Thanks for chiming in, did not feel like getting more involved with other poster with specifics. The 5.7 hemi has 2 efficiency sweet spots. The best is 1200RPM (Think highway speed with 3.21 gears) and the second around 2200RPM with a slight reduction in efficiency which is more than offset by reaching lower gear sooner.

If anyone else wants to chime in with the difference of FORCE and WORK as it relates to physics and acceleration, please feel free.

 

[JF19Longhorn]

Just drove from South Jersey to Greensboro, NC, drove around down there, and then the trip back. 99.9% Hwy in the 55 - 70 mph speed limit range (62mph - 79mph cruise setting) I sat in the right lane with the auto cruise on for most of the trip. (89 Oct / filled up the night before we left)

- tank #1 - 17.13 mpg (hand calc) zero traffic, 3/4 of the drive from south Jersey to NC on this tank, 3 adults, 1 baby, and a bed full of mostly babystuff for a 4 day stay.

- tank #2 - 15.97 mpg (hand calc) zero traffic, last 1/4 of the drive to NC she was avg 18.9mpg on the dash.. but drove around the rest of the tank going to dinners, wedding, etc and idled ALOT keeping the baby / wife cool while we were waiting for people to arrive / get ready to leave / etc. Same 3 adults, one baby, but next to nothing in the bed.

- tank #3 - 17.45 mpg (hand calc & best tank I've had so far) this entire tank was driving through NC to about Richmond, VA when we stopped for lunch / diaper change :baby:. Speed limits was mostly 60 - 70mph (67mph - 77mph cruise setting), zero traffic.

- tank #4 - 18.7 mpg :boxed: (lie-O-meter) *have not filled up yet, but this tank is surprising the **** out of me. We hit a **** ton of traffic, literally right after filling up and getting back on the road. It took us 6+ hours to get from just north of Richmond, VA to South Jersey.. should have taken us 3 1/2 - 4hrs.. traffic was BAD! I let the auto cruise do it's thing for most of the drive... and with the Etrq / MDS / A-S-S constantly engaging and disengaging with all the acceleration > slow down > acceleration > slow down > stop, etc the mileage actually went up.. it'll be interesting to see what the hand calc comes out to when I fill up later this week.

 

[robrob]

Does using the 87 octane Costco gas affect fuel economy? Wondering if I would do better with an 89 Grade Plus.

 

[PaineTrain04]

Does using the 87 octane Costco gas affect fuel economy? Wondering if I would do better with an 89 Grade Plus.

If you have the 5.7L HEMI, you're actually supposed to use the 89 octane fuel.

 

[PorBoy]

Just drove from South Jersey to Greensboro, NC, drove around down there, and then the trip back. 99.9% Hwy in the 55 - 70 mph speed limit range (62mph - 79mph cruise setting) I sat in the right lane with the auto cruise on for most of the trip. (89 Oct / filled up the night before we left)

- tank #1 - 17.13 mpg (hand calc) zero traffic, 3/4 of the drive from south Jersey to NC on this tank, 3 adults, 1 baby, and a bed full of mostly babystuff for a 4 day stay.

- tank #2 - 15.97 mpg (hand calc) zero traffic, last 1/4 of the drive to NC she was avg 18.9mpg on the dash.. but drove around the rest of the tank going to dinners, wedding, etc and idled ALOT keeping the baby / wife cool while we were waiting for people to arrive / get ready to leave / etc. Same 3 adults, one baby, but next to nothing in the bed.

- tank #3 - 17.45 mpg (hand calc & best tank I've had so far) this entire tank was driving through NC to about Richmond, VA when we stopped for lunch / diaper change :baby:. Speed limits was mostly 60 - 70mph (67mph - 77mph cruise setting), zero traffic.

- tank #4 - 18.7 mpg :boxed: (lie-O-meter) *have not filled up yet, but this tank is surprising the **** out of me. We hit a **** ton of traffic, literally right after filling up and getting back on the road. It took us 6+ hours to get from just north of Richmond, VA to South Jersey.. should have taken us 3 1/2 - 4hrs.. traffic was BAD! I let the auto cruise do it's thing for most of the drive... and with the Etrq / MDS / A-S-S constantly engaging and disengaging with all the acceleration > slow down > acceleration > slow down > stop, etc the mileage actually went up.. it'll be interesting to see what the hand calc comes out to when I fill up later this week.

Shoot the next time I have to go to N.C I need to swap trucks with you lol. Even though it’s just the three of us adults and my bed full I’ve only averaged 13.5 with my 3.92 gears ...

 

[kittyjo]

100mph 15mpg hahaha

 

[PowerJrod]

Does using the 87 octane Costco gas affect fuel economy? Wondering if I would do better with an 89 Grade Plus.

I'd be careful with that. You're better off with the 89 octane from a top tier gas supplier...like Chevron, Arco, Mobile, etc...if you have the Hemi..

 

[ColoradoCub]

Man I feel bad for some of you. I just got back from a 400 mile trip towing a 5200 lb camper and got 10.5 going there running 87 fuel and 12 coming back. running 85 fuel, I crossed 3 mtn passes in the 10,000-11,000 ft elevation each way, not too bad IMO.

 

[SD Rebel]

Does using the 87 octane Costco gas affect fuel economy? Wondering if I would do better with an 89 Grade Plus.

Costco sells Top Tier fuel, however the 5.7L recommends 89 octane. The only issue with Costco is they don't offer 89 octane since they don't use blender pumps (which mixes 87 & 91 to create 89).

But since Costco's 91 is usually cheaper that most other stations 87, then I would use that. What I do is fill up with 91 first, then after half a tank fill up with 87. This will average my tank to 89. Then burn that tank all the way down and start the process again with 91 on the next tank. Its not as complicated as it sounds, saves a few bucks.

But if you're lazy, just fill up with 91, still cheaper than brand name 87 while still Top Tier.

 

[ktl5005]

Does using the 87 octane Costco gas affect fuel economy? Wondering if I would do better with an 89 Grade Plus.

89 is recommened, 87 is OK per the manual

 

[PowerJrod]

Costco sells Top Tier fuel, however the 5.7L recommends 89 octane. The only issue with Costco is they don't offer 89 octane since they don't use blender pumps (which mixes 87 & 91 to create 89).

But since Costco's 91 is usually cheaper that most other stations 87, then I would use that. What I do is fill up with 91 first, then after half a tank fill up with 87. This will average my tank to 89. Then burn that tank all the way down and start the process again with 91 on the next tank. Its not as complicated as it sounds, saves a few bucks.

But if you're lazy, just fill up with 91, still cheaper than brand name 87 while still Top Tier.

I stand corrected....I just looked it up. Two years ago Costco wasn't on the top tier list for gas but now they are. Cool!

 

[robrob]

Thanks dudes. Luckily I’ve only had the truck for a single fill up, I will switch to the good stuff

 

[brian42]

My trip odometer (Trip B) has never been reset. I'm getting 15.2mpg overall for the 30K miles I've owned the truck. This is strictly the trip odometer display so it's probably a tad high. The computer display is usually pretty close to my hand calcs (almost right on or a little high) so I'd say I'm getting 15mpg overall with a fair confidence in accuracy.

Tanks fluctuate due to driving conditions so I get anywhere from low 14's to high 16's for mpg when I hand calc at fill-up.

There are so many variables that it's impossible to compare trucks with any level of equality (lifts/levels, tire types/sizes, weather, road conditions/materials, driving styles, topography, and the list goes on).

It doesn't take much city driving to suck down my average. I do a lot of highway driving but a good portion of that is in commuter traffic so that's a wash for some of it.

Some factors that I have learned make a difference:

1. Good gas. I fill up with Top Tier 89 or 91. Mileage is slightly better with non-87 octane (got a "free tank" from the dealership once (they told me it was 87 octane when I asked them). It's not much but if you're splitting hairs it does make a difference.

2. I accelerate to speed. I don't hit it like I'm at the dragstrip or trying to merge onto the freeway, but I don't accelerate like there's an egg under the gas pedal either. I used to gently roll up to speed but now that I get up to cruising speed with a little assertion it does make a difference in mpg (a little higher overall).

3. I cruise on the freeway between 65-70 mph. Anything more than that and my fuel economy takes a noticeable dive.

I don't have eTorque, I don't disable MDS, I don't drive like I stole it (I"m not young any more), but I also don't drive like the gas pedal only moves an inch.

Yes, I can get a 'current mpg' of 25+ mpg on the highway (and 2 mpg in town) but the instantaneous number only shows you your current usage/loading on the engine (or whatever you want to call it). These are big-ish vehicles with big-ish engines that have a big-ish thirst for fuel.

I know that many of us aren't getting the numbers posted on the window sticker but many of us didn't buy a bare bones Tradesman Quad Cab 2WD short bed with 3.21 gearing and hard street tires.

I knew that I was never going to see those numbers as I checked a lot of option boxes. I would like to get the best fuel economy I can without sacrificing my driving enjoyment. There's a reason I opted to buy a full size 4x4 5500+ lb truck.

If fuel economy was towards the top of my list then I would have gone with something smaller and probably a hybrid of some sort.

Just my .02

 

[SD Rebel]

I stand corrected....I just looked it up. Two years ago Costco wasn't on the top tier list for gas but now they are. Cool!

I thought the same thing until just last year when I bought my RAM and wanted to save some money, luckily I was driving by and saw the Top Tier sign

 

[smashweights]

Getting 15.5-16mpg on a tank just doing a short city drive to work. Did 80 miles on the highway doing 70 in aero and averaged 22.5mpg. so not too far off for a loaded out truck.