Re-geared and free-spinned the 3500 4x4 diesel

[slowmover]

I guess I meant to point out out that even though my truck spec, climate & terrain (the Cummins order) is ideal, that you're quite close overall.

[skyking]

Yes, not bad.
It is a complicated time of year for collecting data. Yesterday was all dry roads, which can be hard to come by around here. The trip south is tentatively scheduled for Saturday, and that looks dry too.
Do you find it difficult to totally top off your truck? For these short tests, I think it is necessary to get accurate information. The last two gallons are a pain to get in there.
It is far more difficult than the beetle, for example.
For long term tank to tank data I will just let the pump click off.
The next trip after that will likely be across the mountains on my newly acquired LT245/70r17 Dean Wintercat SST studded snow tires.
Wintercat SST - Winter Tire from Dean
I picked up a set yesterday on that road trip for $250, with low miles and a recent date code. The seller threw in the tire chains that went with it.
Those big Nittos are fine in loose and compact snow, but I have my doubts on ice. I have 3 sets of rims, so I figure for a total cost of $330 including mounting, it is cheap insurance for those winter months. They will last for many years at only 2000~3000 miles a year.

[skyking]

What happened to that post?

[skyking]

Did a run across the mountains Wednesday. Up over White pass, through Yakima and back across I-82 to Ellensburg and over Snoqualmie Pass and back home.
Roadway mostly bare and wet, temperatures in the mid 30s to mid 20s.
About 11,000 feet of elevation gains total
Tires were some old Michelin 265/70R17, about 31.2"
1680 RPM @ 60 MPH
23.55 MPG

[slowmover]

As to filling. Irrelevant for most part. For consistency, same pump at same station parked same direction. Install into filler same way. Turn off at first click.

I wouldn't ever try to get as much fuel into tank as possible.

It's the average that matters.

Fun to try tank by tank, but unless one is running same highways as I was (commuting), we're hoping for a representative snapshot. Further tanks will prove the numbers.

Easiest fill method is best. Repeatability. Thus, earliest shutoff plus same pump.

[skyking]

I have some local driving to do, and another test run on Saturday on flatter ground. I will "fill to the click" when I get on the highway and repeat as suggested.
Running around in town I only get about 17 MPG at best.

I calibrated the ABS at 31.2" for these particular tires. This resulted in
60 MPH = 1680
65 MPH = 1820
The smarty touch allows calibration in 0.05" increments, approximately 0.16%
I set an initial guesstimate and run 20 miles of mileposts and do some math, pull over and make a correction. That is usually all it takes.

I am picking up some 2011 alloy wheels. These are the lightest factory Ram wheels at ~20 pounds. They have the stock Michelins on them, probably calibrate at 31.5" or so.
The latest LTX are called Defenders now. They are 31.6" according to the manufacturer.


Yesterday, The conditions were far from ideal. I was stuck at 20 MPH all the way up White pass behind some trucks, and the overhead dropped down to 14 MPG. Ouch.

Speaking of the overhead display, it is MUCH more accurate with fresh injectors. Before, it was quite optimistic. I figure it like this:

The computer only knows duration and pressure to figure out MPG. I think the old slobbery nozzles put out a whole lot more fuel in a given duration+ pressure than the new nozzles. The other day I ran I-5 up to Lake Stevens and back, and got 23.4 MPG. The overhead was at 23.2 for almost the whole trip.

[Hersbird]

Originally Posted by skyking

Did a run across the mountains Wednesday. Up over White pass, through Yakima and back across I-82 to Ellensburg and over Snoqualmie Pass and back home.
Roadway mostly bare and wet, temperatures in the mid 30s to mid 20s.
About 11,000 feet of elevation gains total
Tires were some old Michelin 265/70R17, about 31.2"
1680 RPM @ 60 MPH
23.55 MPG

That's really good for that route. How do you run the downhill? I'd be way too chicken to EOC on those roads.

[skyking]

You can't EOC these trucks safely. No brake and no steering boost is insane. They have hydroboost systems, so key off = instant loss of braking and steering.
With my beetle it has an accumulator and I can get 6 good brake applications in before vacuum boost goes away.
As it turns out, EOC is a bust on these diesels anyway. Either it is coasting at miniscule idle fuel, or DFCO at no fueling.
As for that run, I let the cruise control do almost all the work.
I rolled off Snoqualmie and bumped the cruise up to 65 MPH.
The smarty touch can tell me requested CC speed, which is handy for testing. Pin the CC close to an excact MPH, it does not matter which one. One click up = 2 mph
one click down = 1 mph
Easy to set an exact speed.

[skyking]

I scored some of the lightest wheels around, the stock alloys off the 2011 4th generation Ram. The same Michelins on those alloys is 61 pounds, for a total reduction of 92 pounds of rotating mass. I will report the results.

[slowmover]

Originally Posted by Hersbird

That's really good for that route. How do you run the downhill? I'd be way too chicken to EOC on those roads.

As with skykings reply, the same is true for gear choice around town. Higher rpms on some roads -- non-limited access -- as need to rapidly decrease speed isn't optional. So, a slower than speed limit choice (say, 37 in a 45) as rpms at 17-1800 is no real penalty, and need that engine drag to slow quickly. Rpm drop gear to gear is significant. Have to always be aware of tactics necessary to have it work in ones favor. An 8000-lb truck, even with great 4-whl disc brakes -- can only stop so fast. Same for lane changes and the like. Same lane and steady rpm win out. But slower travel speed is necessary.

I took Diesel Daves challenge years ago and brought city mpg from 18/19 to 22/23 by tightening up habits. It was mainly a matter of fewer miles. But it was in being rigorous about trip planning that the savings really added up. 22/23 city at a time when Hwy was 24/25.