MPG improvements

Mopar_Stev · 04-24-2011, 07:10 PM

This has been an on going experience for the past two years of what works what does not.

For the longest time, the Ram Van B2500 12-passenger, V8 5.2L/318cid Magnum, 36-gallon tank, with the 46RE, 3.92 rear, and the heavy weighted frame + 8-lug wheeled suspension has not managed to hit above 14mpg in a very long time. I just thought it was high mileage. After doing some digging (reading and experimenting) of what these ultra marathon mileager's are doing, I set out to try a few reasonable things.

We had just finished a family trip from Nashville to FL; 10 of us all packed in with the goods. From fill up to refill a few times, we averaged 18.59mpg. On the tank full that did not have the mountains, rush hour traffic, no construction, no sitting on the interstate due to accidents, the van did an amazing 19.7mpg humming along at 65mph. To see the mileage OD turn past 400 and it was just above a 1/4 tank was shocking. Usually, 340-360 miles per tank was the best this van could do.

Here's a few of the things that helped.

* Brakes
- Tune in those rear self adjusters from keeping the drum brakes from dragging.
- If the brake hoses are over 10 years or the van has sat for a very long time, replace them.
- Find a very low friction and high temp bearing grease and repack the front inner and outer bearings.
My van is using a blue lithium bearing grease from the Tractor Supply store TSC. <---DO NOT DO THIS. I just repacked again with a Molybdenum Lithium grease today!!!<--- DO THIS.
Brand: Valvoline SYN-Power P/N: VV986, It's fully synthetic, moly-fortified, temp range -40F to 400F, Meets NLGI #2 GC-Lithium complex EP grease. Exceeds all domestic vehicle applications.
- Bleed the lines very well.
- Clean the front pad guides on the calipers or ensure that the metal guide clips are not binding the pads from moving.

* Exhaust
- Recently, my CAT and muffler went bad last Fall. I had opted for a high flow CAT, high flow exhaust. Plus where the two pipes come together before the CAT, the OEM has them pinched somewhat restricting good flow. Oh, after the CAT run with 2-3/4 or 3-inch exhaust pipe.

* Tires / suspension
- Chrysler has a TSB mentioning that the load-E tires for handling, safety and mpg are ideal for the Magnum series vans that have the 8-lug wheels. The previous Yokohama tires were not ideal for my van; they wore faster, to soft on the road, traction degraded within 6 months. The BFGoodrich Commercial T/A's load range E are still doing well, traction is holding, tread wear has not even been noticed.
- Alignment is really needed too. Don't go shops with the old school alignment methods. The newer last alignments are dead on.
- Have the suspension looked over for anything that may be failing. (control arms, etc ...)

* Rear Axle
- Chrysler has a TSB out for using 75W90 now in the rears vs. the 80W90. This helps with fuel mpg. While in Georgia, we had visited Summit Racing at exit 216 on I-75. I had picked up a second bottle of Red Line 75W90 synthetic.

* TB
- Other than doing the entire TB replacement with a Fastman TB ( http://www.thefastman.com/Throttlebodies5x.asp ), I've taken the DIY approach and ground down the TB two barrels on the MAP sensor side and didn't touch the IAC side. If you do the TB barrels all around, expect loud rushing noises while at idle and possibly idle issues. Otherwise, this will improve the mpg, Hp, and throttle response. This photo shows all sides ground and smoothed down.

* Engine
- Plugs are the Autolite AP5224 (single Platinum) side gaped like racing plugs. There are at least three threads here in the B-van section talking about this topic. No sense doing that all over again.
- New 7mm or 8mm wires following the TSB for the ignition wire layouts. (critical)
- Cap and Rotor must be of the copper/brass type period. NEVER use the cheap aluminum metal material.
- Cap needs a vent plug. Reduces moisture issues.
- Running with the Purolator L30001 filter for added capacity.
- Using Castrol 5W30 and 10W30 mix non-synthetic at the present.

* Tranny
- ATF+4 only.

* Cooling system
- Replace nearly everything early this year except for the heater cores of the front and rear HVAC systems. All hoses, water-pump, fan viscous clutch, T-stat, radiator, and S-belt.

That 19.7mpg still blows my mind thinking about it.

Only two things left to push this van to 20+mpg. Summit Racing has electric water-pumps and eFans for electric cooling the RAD. Of course, I would have to replace the S-belt one more time, but to a non-standard sized one.

David's van had hit the 20mpg mark over a summer ago. It was difficult to believe. He had listed a few things that got his van there. With the steps taken on my van, it seems very realistic.

Of course not all of the items listed were towards MPG gains. Parts failed and needed replacement in the two years. Just glean what you can to help your MPG improvements.

bignoisey · 04-28-2011, 10:59 PM

Very Impressive, it sounds like you've put a lot of time in on those improvements. Which ones do you think made the most difference?

I've got a 1999 B3500 RV conversion van. Still only 60K on the odometer. The beast weighs in at 9000 lbs and the best mileage I've seen is around 11.5 mpg. Its got a 5.9L engine with 4.10 rear end. I keep the tires at 70 PSI. I don't think I can do all that you did but maybe a couple of things may help. I like the lighter bearing grease idea and also the lighter rear axle lube might help. If I did that is the heavier GVW an issue? The last front brake job I did I made sure the sliders and guides were clean, lubed and free running. But maybe I could back off the rear brake adjusters. Maybe an electric fan?
You suggest replacing the brake hoses. I've seen that in other threads. What is the reason for this?
A couple MPG improvement would make me happy. Any suggestions?

Mopar_Stev · 05-02-2011, 07:38 PM

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