Fuel economy questions?

[HangmanNY]

Fellas,

I have a 2015 ram bighorn with a 5.7 L hemi. We have been towing a small 5 x 10 enclosed utility trailer for the past couple of years. we have made numerous trips between Long Island and the West Coast of Florida.

I always have this thing switched to “tow/haul” mode. And whenever we are trailing, I’m only using premium fuel.

For some reason, we are averaging 13.5 miles per gallon for the first 2/3 of the journey. Then the last 350 miles or thereabouts, the fuel economy starts crashing. And it doesn’t matter which direction we are driving. By the time we get to Florida or Long Island it winds up averaging around 12.1 miles per gallon to 12.3 miles per gallon.
By the way I have routinely changed the transmission fluid and have the new PPE pan, I have changed the transfer case fluids, front and rear differential fluids. I am using the “ high-performance lubricants” motor oil for the past 20,000 or so. And I have routinely changed the air filter. The only thing I haven’t changed so far all the spark plugs. And I’m about 125,000 miles on the truck.

And I can’t figure out why fuel economy seems to be crashing for the last 350 miles of the journey. Once again, it doesn’t matter which direction we are going. It will average 13.5 miles per gallon for most of the journey. Then when we get to our destinations, it’s somewhere around 12 miles per gallon to 12.3 miles per gallon.

I’m looking for explanations on why this could be happening?

Thanks!

 

[RamInfo]

Are you hand calculating mileage or going by the (inaccurate and unreliable) dash display?

Best,
RI

 

[HangmanNY]

Are you hand calculating mileage or going by the (inaccurate and unreliable) dash display?

Best,
RI

Actually the computer fuel efficiency on my truck is very accurate. Whenever we fill up the tank (along that journey) the gallons added match the fuel gauge reading.

 

[chopperman1]

Only use tow/haul if you find the transmission seeking. Smaller trailers don't typically need it.

 

[Daw14]

02 sensors do get worn with age ,might not hurt to put some new ones in. As to the last three fifty no idea, other then you speeding up to reach your destination.

 

[HangmanNY]

02 sensors do get worn with age ,might not hurt to put some new ones in. As to the last three fifty no idea, other then you speeding up to reach your destination.

We have cruise control set at 65 mph the entire trip. Even when speed limit is 70. We don’t speed, especially in Georgia!!! They are vicious there.

 

[tron67j]

Don't need premium, that is a waste of money. Truck is designed to work at maximum efficiency at a lower octane level, follow instructions in manual. All your truck is doing is adjusting things to get it back to where it wants to be with lower octane.

Do manual calculation of MPG, computer is not reliable. Also, my 2003 2500 needed plugs at about 125k, worked better afterwards.

Run diagnostics for any codes, never know. Agree that O² sensors could be bad. And also that you may be doing a bit more pedal pushing the last few miles and impacting your mileage, stands to reason that it always is the worst part of your trip. Good luck.

 

[HangmanNY]

Don't need premium, that is a waste of money. Truck is designed to work at maximum efficiency at a lower octane level, follow instructions in manual. All your truck is doing is adjusting things to get it back to where it wants to be with lower octane.

Do manual calculation of MPG, computer is not reliable. Also, my 2003 2500 needed plugs at about 125k, worked better afterwards.

Run diagnostics for any codes, never know. Agree that O² sensors could be bad. And also that you may be doing a bit more pedal pushing the last few miles and impacting your mileage, stands to reason that it always is the worst part of your trip. Good luck.

I was thinking it may be time for spark plugs. Which plugs work best in the 5.7L hemi? Typically on these long trips we are pulling a 5x10 enclosed trailer.

Are the O2 sensors easy to change? Where are they located?

Thanks

 

[BenchTest]

If those are the factory plugs, get those swapped regardless of how your MPG is. 125k on stock plugs, they're toast. Ambient temps and humidity (denser air) and draw from A/C would be factors to consider as well for MPG changes.

 

[BenchTest]

I was thinking it may be time for spark plugs. Which plugs work best in the 5.7L hemi? Typically on these long trips we are pulling a 5x10 enclosed trailer.

Are the O2 sensors easy to change? Where are they located?

Thanks

Go to RockAuto and plug your information in. There are plenty of options from OEM to "Economy" type plugs. If you're planning on keeping your truck until it's demise, put good plugs in it. Cheap plugs fail to perform well, sooner than good plugs, (lower miles) and you'll be replacing them again. OEM is always the safest route for those who aren't familiar enough with the differences. You can ask 10 people their opinion on "which plug is best" and you'll get 10 different answers. Don't want to pay OEM part prices? Champion, NGK, Autolite, and a few others make good quality plugs. Just make sure you get plugs that meet OEM spec if you aren't using OEM. Can't speak to O2 sensors on that truck as I don't have first-hand knowledge. Wouldn't be the first place I'd look to address your issue.

 

[HangmanNY]

Don't need premium, that is a waste of money. Truck is designed to work at maximum efficiency at a lower octane level, follow instructions in manual. All your truck is doing is adjusting things to get it back to where it wants to be with lower octane.

Do manual calculation of MPG, computer is not reliable. Also, my 2003 2500 needed plugs at about 125k, worked better afterwards.

Run diagnostics for any codes, never know. Agree that O² sensors could be bad. And also that you may be doing a bit more pedal pushing the last few miles and impacting your mileage, stands to reason that it always is the worst part of your trip. Good luck.

So are suggesting a mid grade fuel? Or regular? I thought the hemi’s were supposed to run on mid grade fuel at a minimum

 

[Wild one]

I was thinking it may be time for spark plugs. Which plugs work best in the 5.7L hemi? Typically on these long trips we are pulling a 5x10 enclosed trailer.

Are the O2 sensors easy to change? Where are they located?

Thanks

NGK's should be the OEM plugs,stick with them. DO NOT buy plugs off Amazon or Ebay,they're most likely fake plugs.

 

[04fxdwgi]

So are suggesting a mid grade fuel? Or regular? I thought the hemi’s were supposed to run on mid grade fuel at a minimum

Partially correct..

From the 2016 manual:

 

[2003F350]

If you're watching the computer, what you're seeing is pretty much normal. Here's why:

Your 'average' that the computer is displaying is calculated over the last *** miles (I don't recall what the number is, and I believe it is changed every so often, I've heard 250 miles, I've heard 1000 miles, I've heard longer). So for the first 2/3s of your trip, your unladen mileage is still a factor in the equation. By the time you're that far into your journey, your unladen mileage is long enough ago that your truck's computer has forgotten about it, so your mileage will tank. If you notice, when you're unladen again, it takes a while for the numbers to come back up - the opposite is happening, your truck is slowly forgetting the mileage you got while you were towing.

I would venture to guess that if you hand-calculate your mileage (miles driven divided by gallons put in), you'll find your towing mileage is actually worse than the computer is displaying. I frankly gave up on doing the calculations, I do watch what the computer is saying because while it isn't 100% accurate, it is accurate enough to let me know if something has changed on the truck. I am not as concerned with how much fuel I'm using as I drive an HD truck - if I truly cared about mileage I'd be driving something different.

If you're looking for ways to improve the mileages, with an enclosed trailer there isn't a ton you can do. You could attempt to build a 'wedge' for the front to split the air better, you could add the 'wings' like what some rigs are using, but overall there just isn't much that can be done.

 

[Rustypipes12]

Fellas,

I have a 2015 ram bighorn with a 5.7 L hemi. We have been towing a small 5 x 10 enclosed utility trailer for the past couple of years. we have made numerous trips between Long Island and the West Coast of Florida.

I always have this thing switched to “tow/haul” mode. And whenever we are trailing, I’m only using premium fuel.

For some reason, we are averaging 13.5 miles per gallon for the first 2/3 of the journey. Then the last 350 miles or thereabouts, the fuel economy starts crashing. And it doesn’t matter which direction we are driving. By the time we get to Florida or Long Island it winds up averaging around 12.1 miles per gallon to 12.3 miles per gallon.
By the way I have routinely changed the transmission fluid and have the new PPE pan, I have changed the transfer case fluids, front and rear differential fluids. I am using the “ high-performance lubricants” motor oil for the past 20,000 or so. And I have routinely changed the air filter. The only thing I haven’t changed so far all the spark plugs. And I’m about 125,000 miles on the truck.

And I can’t figure out why fuel economy seems to be crashing for the last 350 miles of the journey. Once again, it doesn’t matter which direction we are going. It will average 13.5 miles per gallon for most of the journey. Then when we get to our destinations, it’s somewhere around 12 miles per gallon to 12.3 miles per gallon.

I’m looking for explanations on why this could be happening?

Thanks!

ANY vehicle gets better gas mileage (unless its electric) during the first 1/2 of the tank. Don't believe me? Try stopping and refilling before you go through the 1/2 way mark then check your mileage. I don't know the scientific reason, just from 50 years of driving.

 

[Rustypipes12]

And stop using the tow button unless you have a lot of weight in that trailer.

 

[HangmanNY]

NGK's should be the OEM plugs,stick with them. DO NOT buy plugs off Amazon or Ebay,they're most likely fake plugs.

I watched a couple of YouTube videos on how to change the plugs. I don’t want to do it frequently. I’m assuming the NGK iridium plugs are good. Should be good for about 100,000 miles. Have you guys had good results with those plugs?

 

[BenchTest]

I watched a couple of YouTube videos on how to change the plugs. I don’t want to do it frequently. I’m assuming the NGK iridium plugs are good. Should be good for about 100,000 miles. Have you guys had good results with those plugs?

NGK is a premium manufacturer and supplier of Original Equipment parts to several major auto manufacturers, numerous industrial manufacturers and small engine makers. If you look up your vehicle on NGK's application guide, trust the part they say "meets or exceeds OEM". They know what they're doing and are top quality. As mentioned above, source them from a reputable vendor. Ebay and Amazon are known for having knock-offs floating around. I personally use RockAuto as they are a no-BS vendor and handle their business quickly. Usually the best prices every time, but not always. Also, if you don't have a quality gap check tool, purchase one. Don't use the Mickey Mouse "coin style" gauge. Use a quality feeler gauge type (calibrated wire loops) and learn how to properly adjust them, should they need adjusted. Modern plugs are very easy to damage if mishandled or attempting to improperly gap. Don't trust the verbiage of "gapped from the factory" or "pre-gapped". Always, ALWAYS check gap on new plugs, right out of the box. Every time, always. Find and use the torque spec for your plugs as well. Over-tightening plugs is bad.-

 

[markabby]

i'd check your vacuum lines, especially ones from the fuel tank to the front.

and unless you have a LOT of weight in that trailer, i doubt you need to use the tow/haul option. I have a 16 foot landscape trailer and the only time i use the T/H is if I have stuff in it.

 

[RamDiver]

And, don't forget the game-changing, 'must have', magnetic swivel spark plug socket.

There's usually a similar product on both Amazon.com & Amazon. ca .

https://www.amazon.ca/gp/product/B0014ZVSVK/ref=ox_sc_saved_title_1?smid=A3DWYIK6Y9EEQB&th=1

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