Terrible 5.7L 2500 MPG

[U&A]

6.4 hemi
3500
Crew cab long bed
4.88 gears
35x12.50x18

Summer blend gas i get 13-14 highway

Winter bled i get 11-12

Id expect the same from your 5.7


Edit:

Carry on. I dis not read all the post like a bad forum member. I see you chasing problems now. Good luck. O wish the best for your 5.7

 

[Wild one]

Previous owner actually did replace the hydraulic lifters too! Hoping it’s not that again haha. Code is also pending, might have just been a random instance but I’ll take it for another drive tomorrow and see if the check engine light shows up.

Do you happen to know if he used OEM lifters or aftermarket lifters. I'm always suspect when somebody throws a set of new lifters in a Hemi and doesn't replace the cam,that's usually a band-aid fix at best.

 

[Cmz2800]

Had an engine code for a P0420. Took out cats and put in anti-fowlers. No engine light so far, but have noticed my fuel economy is absolutely terrible. Was bad before and now seems a little worse. It’s a 2011 Ram 2500 5.7L crew cab longbox 4x4 with 3:73’s and stock tires. I drive it like a grandpa and get 11 mpg on the highway. others seem to atleast get 14 but I just can’t. I’ve gone 150 miles with 35 gallon tank and I’m almost at half. Wondering what could be causing this, or maybe it’s normal and I’m overreacting. Any help would be appreciated!


(What the computer is reading on flat ground)
View attachment 530611

Damn… I currently drive Volvo 18-wheelers for a living and they average 7.5-8 MPG loaded on the highway.
To think that the difference between a loaded tractor/trailer is to you (your Ram 2500) what your truck is to me (my Ram 1500) is pretty damn crazy. Because I average about 16 mpg.

 

[Jeepwalker]

I did a google search with your truck specs. Seems like a lot of Ram 2500 owners with 3.73's seem to be getting ~16 mpg combined (empty, flat land driving, not towing). Is that what you've been reading, OP?

 

[LongTom]

I did a google search with your truck specs. Seems like a lot of Ram 2500 owners with 3.73's seem to be getting ~16 mpg combined (empty, flat land driving, not towing). Is that what you've been reading, OP?

Computers reading 12 mpg on flat roads with the wind behind me. That’s on a good day. I’ve had flashes of 14-15 but it doesn’t last long. Something is definitely up.

 

[rosco11]

Had an engine code for a P0420. Took out cats and put in anti-fowlers. No engine light so far, but have noticed my fuel economy is absolutely terrible. Was bad before and now seems a little worse. It’s a 2011 Ram 2500 5.7L crew cab longbox 4x4 with 3:73’s and stock tires. I drive it like a grandpa and get 11 mpg on the highway. others seem to atleast get 14 but I just can’t. I’ve gone 150 miles with 35 gallon tank and I’m almost at half. Wondering what could be causing this, or maybe it’s normal and I’m overreacting. Any help would be appreciated!


(What the computer is reading on flat ground)
View attachment 530611If you are lucky, you can get 14 to 15 on the highway with a 2wd truck unless it has one of the newer 8 or 10 gear trransmissions. Then around 18, maybe 19. 4wd trucks get worse. Make sure it is in 2wd and not AWD. It makes a differance but either way it is more drag on the drive train. 4wd dailey driving, 11 is a good average. 14 to 15 on the highway....................pointless to take the cats off unless you are running your truck in the higher RPM range, like 3500 and up, often.Will not get any more power or millage by removing them otherwise. At driving speeds, they do not cause enough back pressure to make any difference..............The factory spent a lot of time and money researching how to get the best efficiency out of that 5.7 to give you the best possible combination of power and millage. Anything you do to the truck is going to tilt that ballance. Either less power and slightly better millage, or more power and significantly worse millage. No one does it better..............BTW my 2018 Demon, with over 800hp, gets better millage than your 6000 pound truck. That is how significant weight is towards millage.

 

[Mark47ak]

A CAN OF SEAFOAM IN GAS CAN REMOVE CARBON AND CLEAN INJECTORS ,also check milage using non ethanol gas.

 

[Buhda72]

I have identical truck with lift and 35inch tires I get about 14 on highway after I bought diablo tuner and run it in the tune for trailer mpg with 89 octane. I am not really easy with the throttle mine does best about 72mph.

 

[Wild one]

A CAN OF SEAFOAM IN GAS CAN REMOVE CARBON AND CLEAN INJECTORS ,also check milage using non ethanol gas.

He's in Canada,we haven't been able to buy ethanol free up here for a few years now

 

[RickyJ108]

I get 11 mpg in my 14 mega cab 2500 with a 6.4. I'm thinking it's not that bad especially since you are cheating the engine light off. Just because the anti fowlers got the light off doesn't mean that it is in proper working order, the cats may still be bad causing the engine to work harder. Again you have a 2500 4x4 on a 5.7.

 

[Jeepwalker]

Unless they changed it recently. The front O2's are what determines if the engine runs in open vs closed loop. The rear cat sensor are only for monitoring the efficiency of the cats.

 

[Tominator223]

No cats & anti-Fowler’s. = bad mileage . Get some good aftermarket cat’s. No short ones. Put 02’s back without Fowler’s . I had a 03 5.7 2500. 14 mpg.avg. My 04 5.7 1500 also avg 14mpg. The newer cat’s are not the same as the 70’s-80’s cat’s. You should drive it like you stole it at least once or twice a month to burn off excess carbon as well.

 

[NCRaineman]

Just deleting the cats and using anti-fowlers on the rear O2 sensors isn't a fix. If you don't want to run cats fine, that's your decision. If you are going to run catless you need a proper TUNE for catless because increased exhaust flow from the cats not being there will cause the engine to lean out, so the computer dumps more fuel to compensate. Thus your poor mileage.

If you are making ANY significant changes to a modern vehicle you've got to TUNE for them.

 

[moparman]

Ive got a 2016 2500 with the 5.7, 3.73 gears, 6.4 intake manifold with an s&b intake and i average 11.8-12 mpg driving it to work every day. if i do a long highway trip it will come up to about 16 mpg. towing and plowing i usually end up in the single digits. If youre getting 11 mpg currently with no cats at all thats probably about the best its going to be unfortunately

 

[mopareg]

I can't believe you guys that buy a truck and expect to get great gas mileage ! I have a 2017 with the 6.4 hemi and average 11-12 around town and a best of 17.8 highway.

 

[ramffml]

I can't believe you guys that buy a truck and expect to get great gas mileage ! I have a 2017 with the 6.4 hemi and average 11-12 around town and a best of 17.8 highway.

Did you not read the first post? He drives like a grandpa and can't get better than 11 on the highway. Vs your almost 18 mpg, that's a massive difference, he's getting only 61% of what you do.

 

[Jeepwalker]

Just deleting the cats and using anti-fowlers on the rear O2 sensors isn't a fix. If you don't want to run cats fine, that's your decision. If you are going to run catless you need a proper TUNE for catless because increased exhaust flow from the cats not being there will cause the engine to lean out, so the computer dumps more fuel to compensate. Thus your poor mileage.

Shouldn't the upstream O2's adjust the air/fuel mix properly? Modern cats don't have a lot of restriction.

 

[Dusty]

Computers reading 12 mpg on flat roads with the wind behind me. That’s on a good day. I’ve had flashes of 14-15 but it doesn’t last long. Something is definitely up.

Have you ever hand calculated the gas mileage?

Regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33-gallon fuel tank, 18” wheels. Build Date: 3 June 2018. Now at 10140 miles.

 

[62Blazer]

As mentioned, the upstream (front) O2's are the ones responsible for controlling the fuel. The downstreams are mainly just to monitor the cat performance, meaning if they are actually reducing emissions. Newer style catalytic converters (meaning anything made in the last 20 years!) generally do not clog up or restrict exhaust flow when them "fail". The honeycomb tends to break up and basically open up the exhaust. The code from the original post is saying that the cat is no longer reducing emissions, but it is NOT saying the cat is clogged up. If the cat is not removing emissions that is because the honeycomb has all been blown out the end of the exhaust and it's not "converting" the exhaust gases anymore. Removing the cats and putting on anti-fowlers is the same as firing the parts cannon at the truck. That means you just start randomly replacing or removing parts hoping you get lucky.
I would look at fuel trims to see if it's running rich or not as a first step. If you don't have the capability to do this (just takes a moderate scan tool that has live data) and a little research to understand the numbers. Not talking bad about anyone, but if you can't do this then find a decent mechanic. There are a lot of decent mechanics out there that can at least do basic trouble-shooting. I know most people on here just bash all shops, or don't want to pay a shop. However they will blindly throw hundreds of $ of parts at a rig hoping they get lucky.

 

[Dusty]

There are a lot of decent mechanics out there that can at least do basic trouble-shooting. I know most people on here just bash all shops, or don't want to pay a shop. However they will blindly throw hundreds of $ of parts at a rig hoping they get lucky.

I've seen countless times when a problem was later resolved by replacing a bad newly installed aftermarket part. Someone in the family that stubbornly insists that all OEM parts are nothing more than more expensive versions of aftermarket, got bit last year with a problem that he could not fix. Frustrated, I sent him to a knowledgeable tech. friend of mine with a scope who found the brand new aftermarket crankshaft position sensor was the culprit in 20 minutes.

Regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33-gallon fuel tank, 18” wheels. Build Date: 3 June 2018. Now at 101155 miles.