A reader asks: Do you have an SAE 50 heavy duty Diesel Engine Oil for trucks that meets the API CF-2 specification?

AMSOIL Synthetic 20W-50 Premium Protection Motor OilOur answer: We do not have a “straight” SAE 50 diesel engine oil. But we do have a heavy-duty 20W-50 that would be ideal for any application requiring SAE 50. AMSOIL SAE 20W-50 Premium Protection Synthetic Motor Oil covers the API CF-2 specification along with a multitude of gasoline and diesel engine specifications. This is a heavy-duty engine oil that is suitable for older diesel truck applications.

Although it is labelled as a 20W-50, this product is very shear stable and can easily be used for applications suggesting SAE-50. “Straight-weight” oils have been supplanted by multi-grade engine oils.

Straight grade oils were once specified because early renditions of multi-grade oils were prone to shearing. They would thin-out and break down under stress, heat and long service. This is why some older heavy-duty applications suggested straight grade oils.

High-quality, modern synthetic engine oils (such as AMSOIL SAE 20W-50 Premium Protection Synthetic Motor Oil) do not use “viscosity index improvers”. Viscosity index improvers are motor oil ingredients that expand with heat to prevent the thinning of some lower quality multi-grade motor oils. Viscosity index improvers are still used by some lesser oils. AMSOIL 20W-50 has world-class resistance to shearing, boil-off and consumption, so it will stand up as well as any straight grade SAE 50 motor oil.

AMSOIL SAE 20W-50 Premium Protection Synthetic Motor Oil pours down to -36°C, providing remarkable cold weather oil flow for a 50-weight oil.

Long Service Life

AMSOIL SAE 20W-50 Premium Protection Synthetic Motor Oil is formulated for long service life of up 15,000 miles (24,000 KM) for severe service. Up to 25,000 miles (40,000km) for general use.

Covers Many Diesel And Gasoline Engine Industry Specifications

  • API CI-4 +, CH-4, CF, CF-2
  • Caterpillar ECF-1
  • JASO MA (Motorcycle)
  • MAN 271/3275
  • MTU Type 2
  • Cummins 20071, 20072, 20076, 20077
  • Volvo VDS-2, VDS
  • Mack EO-M+, EO-M
  • ACEA A3/B3, E3, E5
  • MB 228.1, 228.3, 229.1
  • Detroit Diesel 93K214

We can sell AMSOIL SAE 20W-50 Premium Protection Synthetic Motor Oil at wholesale prices in Canada and the United States. Contact us for prices using the form on this page.

A reader asks: Do you carry an ATF that meets the DEXRON HP spec? I’m having trouble finding a transmission fluid that meets that specification.

AMSOIL Signature Series Fuel-Efficient Synthetic ATF


Our answer: Yes we sure do. AMSOIL Signature Series Fuel Efficient Synthetic ATF is a high-quality upgrade over AC Delco DEXRON HP. This product also covers the DEXRON VI spec. DEXRON HP ATF is specified for the Hydra-Matic 8L90 eight-speed automatic transmission. The HL90 unit is found in late-model, high-performance GMC, Cadillac and Chevrolet cars, trucks and SUVs.

We can sell the world-class AMSOIL Signature Series Fuel-Efficient Synthetic Automatic Transmission Fluid at wholesale prices and ship it right to your door from warehouses in Canada and the United States. Our wholesale prices smoke the prices of AC Delco Dexron HP ATF found at GM dealers. Contact us using the form on this page or call us at 1-800-748-5781.

AMSOIL Signature Series Fuel-Efficient Synthetic ATF Features

  • High-tech wear control
  • Smooth shifting
  • Optimized fuel economy
  • Outstanding cold weather performance
  • High resistance to extreme heat and heavy loads
  • Prevents transmission shudder
  • Outstanding prevention of varnish and deposits

A reader asks: I have a 2008 Dodge Ram 2500 with the G56 six-speed manual transmission. My truck is fairly stock. I’m looking to replace the ATF fluid in the transmission with gear oil. Mercedes builds these transmissions and recommends MobilTrans SHC DC SAE 50 transmission oil in Europe. This product is hard to find in North America. Do you have an oil that matches up?

G56 6-Speed Manual Transmission

The G56 manual transmission for Ram Heavy-Duty trucks. (photo credit: dieselhub.com)

Our answer: Chrysler’s suggestion of ATF+4 automatic transmission fluid in G56 manual transmissions has been an ongoing controversy since this manual transmission was first added to heavy-duty Ram trucks back in 2005. But despite the internet chatter, the experts we spoke with all agree that ATF is still the best option for G56 transmissions. AMSOIL Technical Services and G56 experts like Midwest Transmission Center Inc. agree that there isn’t any upside to using thicker transmission oil. For over a decade, Chrysler has steadfastly maintained that an automatic transmission fluid meeting their ATF+4 specification is correct for the G56. Consider also that Ford has been suggesting ATF in the manual transmissions of their Super Duty pick-ups for several years. This is not a situation unique to Ram G56 transmissions.

Why Is ATF A Controversial Choice For G56 Transmissions?

The G56 transmission is made by Mercedes-Benz in Europe. North American Ram owners have noted that a heavier oil is suggested for European trucks equipped the G56. This is why many Ram users explore the option of using a 75W-90 or even an SAE 50 transmission oil. Some internet sources are actually making the suggestion to overfill the transmission with heavier oil to dampen noise and enhance protection. Heavier oil and over-filling is a recipe for elevated transmission temperatures.

Overall, a common assumption is that Chrysler chose to use ATF in the G56 because it was cheap and readily available. The other commonly held belief is that ATF is simply too thin to provide adequate protection. We see no evidence that this is the case. Remember that Mercedes and Chrysler were part of the same corporation when the G56 was first mated with Ram trucks. After exhaustive testing, Chrysler could have specified any oil they wanted, but they still suggest ATF+4 to this very day. If ATF was causing havoc in G56 transmissions, there would have been a specification change by now.

Why Did Chrysler Go With ATF In G56 Transmission in North America?

Four reasons.
1. Capable wear control
2. Smooth shifting
3. Resistance to extreme cold
4. Cooler operation compared to thicker oils

While European G56 applications may use much thicker oil, North American trucks are exposed to extreme cold that isn’t a factor in Europe. Consider that both SAE 50 weight oil and 75W-90 gear/transmission oil have a drastically thicker viscosity than the ATF+4 recommended by Chrysler.

SAE 50 Transmission Oil

  • At 40°C, SAE 50 is 388% thicker than ATF+4
  • At 100°C, SAE 50 is 257% thicker than ATF+4

75W-90 Manual Transmission Oil

  • At 40°C, 75W-90 is 228% thicker than ATF+4
  • At 100°C, 75W-90 is 185% thicker than ATF+4

Remember that gear oils use a different viscosity scale from engine oils. A 75W-90 gear oil can fall into the SAE 40-50 weight range.

As the numbers above show, both SAE 50 and 75W-90 are a lot thicker in viscosity than an ATF+4 transmission fluid. In cold weather, ATF will provide much smoother shifting performance.

Why Some G56 Transmissions Fail

The alleged G56 transmission problems generally do not stem from oil related issues. A common problem is clutch failure due to increased horsepower (from major engine mods) or heavy towing beyond the load capacity of the truck. Transmission experts we spoke to insist that the use ATF is not a cause for transmission failure in G56 units.

Will Thicker Oil Dampen Vibration?

The G56 transmission coupled with the Dodge Ram heavy-duty chassis and drive train can be prone to noise and rattles. But this has more to do with the various drive train forces and mechanical activity resonating through the aluminum transmission body than the viscosity of the lubricant. Thicker transmission oil has a minimal effect on issue.

Does Oildepot Sell An Oil For Ram G56 Transmissions?

Our best option for the G56 manual transmission is AMSOIL Signature Series Synthetic Multi-Vehicle Automatic Transmission Fluid. This ATF+4 formulation ticks all the boxes for what is needed in a G56. AMSOIL ATF is formulated to resist shear-down and oxidation in the face of extreme heat. This keeps the transmission free of deposits and varnish. At the other end of the temperature spectrum, Synthetic Multi-Vehicle ATF has a cold pour point of -53°C. So shifting is easy and consistent during extreme winter weather. If you’re going to use ATF, why not use a world-class formula? We can sell AMSOIL ATF at wholesale in Canada and the USA. Contact us using the form on this page for more information.

We would be happy to sell you a thicker oil. But unless you are drag racing, sled pulling or have extreme modifications, our research suggests that ATF is just fine for normal operation.