Most diesel guys aren't going to swap to synthetic lubricants in their drivetrain just to see better fuel economy numbers. They're going to do it for the added level of protection, better lubrication properties, lower operating temperatures, and increased drivetrain longevity when towing or hauling heavy loads. For us, the fact that our '07 1/2 Cummins often tows a 10,000-pound trailer through the mountains one week and endures 125 degree heat the next, made the decision to upgrade our lubrication a no-brainer.
| pml Amsoil Products atf And Lubricant
We chose to convert our Dodge's transmission, transfer case, and rear axle to synthetic lubricants from Amsoil. We reasoned that swapping the lube in the front axle wasn't necessary, since we run a Dynatrac Free-Spin kit up front, and the only time the front differential is turning is at the boat launch. We obtained a good supply of Amsoil synthetic 75W-90 gear lube for our rear axle, and Amsoil universal automatic transmission fluid for the transmission and transfer case.
Then we put in a call to PML for one of the company's slick, increased-capacity rear differential covers and its increased-capacity transmission oil pan. Not only do the PML products hold more fluid, the cast-aluminum construction and built-in fins improve cooling by transferring heat from the fluid better than the factory steel pans. And the company's thick castings and quality machine work result in a leak-free seal and a perfect fit.
As soon as our odometer passed the 15,000-mile barrier, we drained out our dino oil and topped off our crankcase with Amsoil's synthetic API CJ-4 engine oil that our 6.7L Cummins DPF requires. But we also added Amsoil's BMK-11 bypass oil filtration system.
Most diesel owners have heard of a bypass filtration system, but in case you haven't, a bypass filtration system does not have to pass the full volume of oil from the oil pump through a filter, so it's able to filter to a much finer degree. A regular full-pass factory-type filter is able to filter to roughly 15 to 30 microns, depending on the brand and quality.
A bypass filter element, such as the EABP100 used by Amsoil, can filter down to 2 microns. In a modern, emissions-laden diesel such as ours that's pumping EGR particulate and other nastiness back into the engine oil, in theory, the bypass filter's ability to scrub the engine oil cleaner should result not only in better engine longevity-but also in a cleaner combustion and fewer regeneration cycles.
While we really didn't see any improvement in mileage, we're much more comfortable knowing that our expensive engine, transmission, transfer case, and rear axle are much better equipped to handle the rigors of heavy towing.
The Mileage Report
Here's the running tally for each installment of this series. Mileage numbers are generated on the same 250-mile mixed freeway and city street circuit and are hand-calculated by noting miles driven and fuel used from the same pump at the same fuel station. Numbers are the average of at least three test circuits.
* Stock.......................................................................................
15.55 mpg
* S&B cold-air intake..................................................................
16.31 mpg
* S&B cold-air intake, Snugtop Xtra Vision.................................
17.30 mpg
* S&B cold-air intake, Snugtop Xtra Vision, Toyo Open Country A/T..............................................................................................
16.20 mpg
* S&B cold-air intake, Snugtop Xtra Vision, Toyo Open Country A/T, Dynatrac Free-Spin.....................................................................
17.13 mpg
* S&B cold-air intake, Snugtop Xtra Vision, Toyo Open Country A/T, Dynatrac Free-Spin, Fitch Fuel Catalyst......................................
18.55 mpg
* S&B cold-air intake, Snugtop Xtra Vision, Toyo Open Country A/T, Dynatrac Free-Spin, Fitch Fuel Catalyst removed, engine flash from AV to AX, Amsoil lube...........................................................................
16.77 mpg
* S&B cold-air intake, Snugtop Xtra Vision, Toyo Open Country A/T, Dynatrac Free-Spin, Fitch Fuel Catalyst removed, engine flash from AV to AX, Amsoil synthetic transmission, transfer case, differential, engine oil, and bypass filter............................................................................................
17.02 mpg
Hidden Benefit.............................................................................
1.47 mpg
