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Old 06-07-2011, 05:26 AM   #15 (permalink)
Join Date: Oct 2009
Location: Fort Worth, Texas
Posts: 2,442

2004 CTD - '04 DODGE RAM 2500 SLT
Team Cummins
90 day: 19.36 mpg (US)
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Nice numbers thus far!

I'd be careful about having replaced the mechanical fan if heavily loaded or contemplating towing. DODGE would have gone to them (as would makers of big trucks) for FE reasons long ago if they were capable of moving as much air as a clutched mechanical fan. They aren't. I leave mine as is for the practicality of the wide range of work a truck can perform. A truck is either income-offsetting or income-producing. If neither, then another vehicle is warranted. Frankly, the fan change is a crippling move.

In that same vein there are problems that bear investigation, especially on the 4WD models, namely, steering and front suspension component that wear somewhat fast and are re-engineered on later models. Plenty of threads on upgrading on Dodge-specific forums. (Same for HVAC performance, etc). All of these are "economy" in that we are increasing the per-mile cost of ownership, however reluctantly.

The first step for truck FE, IMO, is very careful record-keeping. Understanding the costs as expressed in a cents-per-mile format. An understanding of truck use (percentage highway vs percentage city) is only seen through records, not "what I think it is". Average mph and average mpg go hand-in-hand together. One begins by forecasting ownership life and annual miles.

For truck FE: Truck spec is first, terrain/climate is second, and driver skill is third. The first two cannot be changed, only accommodated. The third is ripe for exploitation if one can get some distance from the usual emotions around driving, primarily the convenience of 24/7/365 usage. Restrictions of use -- such as no single trips (combined trips only) -- are a good first step to see what works. And roll into that a "No Left Turn" policy such as UPS uses.

The difference between the best and worst professional drivers is 30%. Call it a one-third difference in the amount of fuel used to accomplish the same task. Same truck, same work.

Thus I have little patience or belief in aftermarket gizmos that only add to cost -- some with the propensity to shorten vehicle component life -- and the use of which tends to overshadow driver skill improvement (and the gizmo is given credit). A stock truck is the best baseline, and for a factory-delivered Dodge maybe a camshaft change plus timing advance is worth 1-2 mpg annually assuming LRR Michelin tires. (Modified trucks are so far out of spec as to be worthless for comparisons unless one can find an exact match as to spec, terrain and use).

The aftermarket gizmos also increase depreciation and add to the "initial purchase price + finance cost" line of a spreadsheet. One can go through the items mentioned each by each, but let's admit that wishful thinking is part of the "equation" (unless, again, we can corroborate the changes with a similar spec truck in a similar climate/terrain and cross-our-fingers hope that driver skill is similar and that records are honest).

For what it's worth I'd can the go-fast stuff and look to other changes as mentioned; tire spec being the single-most critical change after safety is covered. Bed cover, grille block, air dam, belly pan, etc, can all be experimented with cheaply (and some great stuff to read around here per some other owners).

Start with wheel-by-wheel weights from a certified scale when "empty" (full fuel plus driver plus normal stuff in truck), and scale again (axle-by-axle) when loaded. A stack of scale tickets is handy for comparison purposes. I did this initially to set trailer hitch rigging, but found that it was also useful in predicting FE for a given trip. IMO, if one cannot predict the mpg of a given trip, then more homework is needed. Same thinking for tire & brake life: less than 70k on either (for an on-road vehicle) then the driver is in need of remedial training.

Proper tires, proper alignment, and detailed attention to mechanical drag (system by system) is the first "real" step after complete records establishment. Maybe manual hubs will help, for example. I've seen reports of yes & no. Aero improvements are only relevant to a truck that spends enough time above 50 mph to actually recoup costs. An in-town commuter, a local contractor, is unlikely to see enough change to matter.

FE will be the percentage change of average (overall) mpg change from baseline. If my annual mpg changes from 22.48 to 23.61 mpg over 15k miles, then I am on the right track. 5% has meaning, here, where "1-2 mpg" does not. The particular "blend" of steady state highway speed versus in-town stop-n-go is nullified when looking at changes in this manner.


Last edited by slowmover; 06-07-2011 at 06:12 AM..
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