fuel mileage

[derek_m]

2011 rcsb hemi 3:55 gears 2wd and 20"s. 5 speed tranny and 89 octane fuel.

was getting around 19-20mpg on average.

decided to try an experiment on last tank of fuel. any time i was below ~45mph i put the truck in tow/haul to shut off mds. results was an average of 21.4 mpg. went 492 miles and it took 23 gallons to fill it up.

i thought this was pretty interesting, figured i would share.

 

[AirborneSilva]

Must keep the motor in a sweet spot for fuel economy.

 

[HemiRoar]

i turned my mds off when i got my tuner. i was getting about 18L/100 km stock which is around 13 mpg i think, as of last night it read 16.2L/100 km which is 15'ish mpg. go figure. so i can agree on the increase in gas mileage without mds.

AND that 4 cylinder drone has been replaced by the low key V8 o/d rumble when cruising at highway speeds and its completely quiet when crusing anywhere from 50km/h to 80km/h (30 - 50 mph).

 

[lelikmed]

I can't drive below 45...... I mean anywhere ....

 

[Arctic-Rodz]

I can't drive below 45...... I mean anywhere ....

not even at school zones

 

[loveracing1988]

I watch the mds come on on mine and the fuel mileage goes up by 2 to 3 mpg's according to the EVIC.

 

[JimE]

I watch the mds come on on mine and the fuel mileage goes up by 2 to 3 mpg's according to the EVIC.

Yup! I think they got the idea behind the MDS logic programming exactly backwards for most drivers. In essence when the MDS is inactive the transmission is often unnecessarily downshifting to a lower gear, which of course is going to increase fuel consumption. Keep an eye on the tach and watch the RPMs go up and/or drop as the transmission changes gears. For most drivers never pulling a trailer or having a lot of weight in the bed, once a speed of 30 mph is achieved miles per gallon it would be lot better if the transmission went to the highest gear never downshifts until the vehicle is moving less than 30 mph. We should be realistic, RAMs, like all similar vehicles, are designed to be a work vehicle and not as great economical general family transportation for the most part. Personally I wouldn't use any Pickup as a daily long distance commuter vehicle.

 

[audio1der]

Thanks for sharing this!
I look forward to turning MDS off once I get a tuner and seeing if we get the same result.

 

[loveracing1988]

Yup! I think they got the idea behind the MDS logic programming exactly backwards for most drivers. In essence when the MDS is inactive the transmission is often unnecessarily downshifting to a lower gear, which of course is going to increase fuel consumption. Keep an eye on the tach and watch the RPMs go up and/or drop as the transmission changes gears. For most drivers never pulling a trailer or having a lot of weight in the bed, once a speed of 30 mph is achieved miles per gallon it would be lot better if the transmission went to the highest gear never downshifts until the vehicle is moving less than 30 mph. We should be realistic, RAMs, like all similar vehicles, are designed to be a work vehicle and not as great economical general family transportation for the most part. Personally I wouldn't use any Pickup as a daily long distance commuter vehicle.

I have a 8 speed also, it seems to want to keep the rpm's as low as possible and the mds on as much as possible... I've seen the mds come on at 15 mph quite a bit. I've actually slowed down to 65 mph going back and forth to work and the instant mileage went from 17 to 19 going 70 to 19 to 22 going 65,d's is on pretty much all the time except going up hills and when I am running into the wind.

 

[JimE]

I have a 8 speed also, it seems to want to keep the rpm's as low as possible and the mds on as much as possible... I've seen the mds come on at 15 mph quite a bit. I've actually slowed down to 65 mph going back and forth to work and the instant mileage went from 17 to 19 going 70 to 19 to 22 going 65,d's is on pretty much all the time except going up hills and when I am running into the wind.

A curiosity about V8 engines is when a transmission is at a 1:1 output to drive shaft nearly all of them will be producing their best fuel economy at between 1700 and 1900 RPMs. Doesn't seem to make any difference the displacement of a given engine. Variation is typically from ambient air temperature and density. We'd all get great gas mileage with the ambient air temperature at around 55 degrees and 90 to 100 percent humidity. With that said, the tach with an 5.7L Hemi with a six or eight speed tranny should be showing only 1500-1600 rpms on pretty flat land with the cruise set at 70, even with a 4.10:1 rear axle. Outstanding! For once a vehicle manufacturer actually got transmission gearing concepts more or less right.

For what it may be worth, we have a Hyundai Genesis V6 (non turbo) 5 speed auto and it has virtually the same transmission control features as our Rams. But because it is a V6 the engine rpms are considerably higher than the 5.7L Hemi at the same miles per hour and because of that the Genesis' fuel economy is only marginally better than the Ram truck. Of course that smallish appearing car is anything but light weight, coming in at roughly 4,000 lbs.

Back to 4th Gen Rams. One has to be really careful around town to not accidentally be seeing those RPMs taking off like a skyrocket when starting from a dead stop. 0 - 30 mph seems to be almost instant when not towing anything, assuming you don't have a slower less responsive vehicle in front of you. A Ram 1500 or 2500 will not fit into the trunk of any car!

 

[Saltillo Express]

this is good stuff. The MDS is certainly a feature. Albeit an annoying one. We rode around for years with the 360 engine giving us what, 10, maybe 11 miles to the gallon? Don't miss that at all. Now I complain if I'm not getting 16 around town in the '13.

 

[JimE]

this is good stuff. The MDS is certainly a feature. Albeit an annoying one. We rode around for years with the 360 engine giving us what, 10, maybe 11 miles to the gallon? Don't miss that at all. Now I complain if I'm not getting 16 around town in the '13.

The truly sad thing is had the engineers in Detroit pulled their heads out of their anus over fifty years ago no one would have ever suffered miserable fuel consumption even with big block engines. Seems the dummies never had an understanding of what is referred to as "power transmission" in most engineering circles. There was never a legitimate reason for 10-12 mpgs and lower with any vehicle being used by the typical consumer.

To give one an idea of what I mention, I collect vintage automobiles and among those are three Lincolns with 460 4V engines all with basic C6 transmissions. I have been toying with the idea of swapping the transmission in one of them for the 1995 version of a E4OD transmission used in F-250 trucks and E-150/250 vans. Given it is possible to tweak a 460 to yield 20-21 mpg on the highway I figure the swap will result in 25-27 mpg. highway. Cost will be around $1,200 without a rebuild, plus labor since I'm too darn old to wrestle trannys in and out of a vehicle without a lift and transmission jack.

 

[Saltillo Express]

Jim very interesting. I too collected vintage (junk) vehicles. All Chrysler though. I once put a 46RE into my '66 D-100. Remember those? Big bug eyed tanks? Anyway, I got it to go in and out of OD with a solenoid switch. Got it to around 20 mpg.

Was the 460 Ford the one they put in that 2 door lincoln continental back in the 70's?

 

[JimE]

Jim very interesting. I too collected vintage (junk) vehicles. All Chrysler though. I once put a 46RE into my '66 D-100. Remember those? Big bug eyed tanks? Anyway, I got it to go in and out of OD with a solenoid switch. Got it to around 20 mpg.

Was the 460 Ford the one they put in that 2 door lincoln continental back in the 70's?

All Lincolns manufactured between 1969 and 1977 and some '78s had a variation of the 460. The ones I have tweaked to hit over 20 mpg highway were not well documented and only a few were produced and place into '76 Mark IVs. They were also very high performance versions capable of moving a nearly 6,000 pound car at 190 mph, so I was told by a Ford executive that was involved with one of Iacocca's pet projects that lead to their production.

Though I have always admired and appreciated MOPAR drive trains my 2012 Ram 2500 HD with a 5.7L is my first MOPAR Product. I've always thought the most opulent and beautiful interior ever placed in any car was found in the 1960 or maybe it was 1961 Chrysler Imperial. Made Caddies and Lincolns look like cheap junk.