A reader asks: I am looking for a two-stroke injector oil that is the same quality as the Evinrude XD50 Synthetic Blend 2-Cycle Oil. Is AMSOIL HP Marine the closest match? I’ve got an older outboard, but still looking for a decent injector oil.

Our answer: A fairer comparison would be AMSOIL HP Marine to the full-synthetic Evinrude XD100 2-Cycle Oil. HP Marine will definitely be an upgrade over the semi-syn XD50.

AMSOIL HP Marine Synthetic 2-Stroke OilHP Marine is a 100% synthetic 2-stroke oil and is very much an elite product. It is at the pinnacle of two-cycle oil technology. The best part is that at our wholesale prices, it can be less expensive than the synthetic-blend XD50 oil.

AMSOIL has performed extensive testing in Evinrude ETEC engines versus XD100 and the results were very impressive. Even using the “lean setting” in ETEC, HP Marine delivered superb wear protection.

Some may consider HP Marine to be overkill in an older outboard. We would suggest that it’s low-deposit, low smoke, clean burning, low friction contributions would be welcome in any outboard engine. But we do have another option.

An Even Less Expensive Full Synthetic Option To XD50

For those wanting an even less expensive option for older outboard engines, we do have another full-synthetic 2-stroke oil. AMSOIL Synthetic 2-Stroke Injector Oil offers features like low smoke/odor, optimum throttle response and synthetic wear control. It is suitable for DFI (direct fuel injection) outboard engines, as well as older snowmobiles or AMSOIL Synthetic 2-Stroke Injector Oilpersonal watercraft. This Synthetic 2-Stroke Injector Oil is a great value and a top-notch performer in older 2-stroke outboards.


Either AMSOIL HP Marine or Synthetic 2-Stroke Injector Oil would be an upgrade over Evinrude XD50 Synthetic Blend 2-Cycle Oil. Both AMSOIL products can deliver a performance upgrade at a better price (with our wholesale programs) than the oils found at Evinrude dealers.

Contact us for a wholesale price list using the form on this page. We can ship synthetic outboard 2-cycle oil to any location in Canada or the United States at a great price.

A reader asks: I’ve got a 2012 Cadillac Escalade that calls for a 75W-85 API GL-5 gear oil in the rear differential. AMSOIL’ s application guide suggests Severe Gear 75W-90. Is this correct? Can I safely replace 75W-85 with 75W-90?

Our answer: Yes, 75W-85 gear oil can most definitely be replaced by 75W-90. In fact, we know that some GM dealers will use 75W-90 gear lube in applications where Chevrolet/Buick/GMC/Cadillac suggests 75W-85.

Why Does GM Suggest 75W-85 GL-5 Gear Oil In Some Cars And Trucks?

We can only speculate on why GM specifies 75W-85 for some vehicles. Here are our theories.

  1.  To boost mileage. Auto manufacturers have to meet government-mandated fuel economy standards across their product lines. If a car maker doesn’t meet these fuel economy targets, they can be subject to big fines. These fines can be in the tens of millions of dollars. That’s why automakers are going to lighter oils in the engines and transmissions and differentials.
    You may not notice the fraction of a mile-per-gallon improvement because of the thinner oil in your diff. But the automaker bean counters do and they are banking on every trick in the book to boost collective fuel economy.
  2.  A 75W-85 GL-5 gear oil is relatively rare. Therefore, consumers will feel that the safe choice to go back to the dealer for service. There will be a natural fear to deviate from the exact viscosity in the owner’s manual. Again, we know for a fact that some GM dealers simply use 75W-90 anyway.

AMSOIL SEVERE GEAR® 75W-90 Synthetic Extreme Pressure Lubricant

Why Use AMSOIL Severe Gear 75W-90 Instead Of AC Delco 75W-85?

  1.  Very close viscosity. Most diffs were designed with 75W-90 in mind. Going to 75W-85 was a fuel-economy-boosting endeavor. AMSOIL Severe Gear 75W-90 is designed to replace, 75W-90, 75W-85, 80W-90, SAE 80 or SAE 90 gear oils. It can replace any of these with no worries or risk.
  2. No fuel economy penalty. As AMSOIL Severe Gear 75W-90 is an ultra-low-friction synthetic formula. There will not be a measurable loss of fuel economy by going with this slightly thicker oil.
  3. World-class wear control. Severe Gear 75W-90 is formulated to provide elite wear protection. It is designed to withstand high horsepower, heavy loads and extreme heat or cold.
  4. Reasonable cost. At our wholesale prices, AMSOIL Severe Gear Synthetic 75W-90 is about half the cost of AC Delco 75W-85 API GL-5 Gear Oil.

What About Limited-Slip Additives?

If your GM car or truck has a limited slip rear axle, definitely pick up a bottle of AMSOIL Slip-Lock Differential Additive or the AC Delco Limited Slip Axle Lubricant Additive. AMSOIL Severe Gear contains limited-slip additive, but we find it’s still a good idea to add about 2/3 bottle of limited-slip additive for good measure. If using AC Delco 75W-85 GL-5 Gear Oil, add the full bottle of limited-slip additive.

KTM MotorcycleA reader asks: A lot of motorcycle owners use Shell Rotella T6 diesel oil in their engines/transmissions. Is there any downside to using diesel motor oil in motorcycles? As Shell Rotella can be found fairly cheap, why would I want to use the more expensive AMSOIL Motorcycle Oils?

Our Answer: Diesel motor oils can provide (somewhat) adequate service in motorcycle engines and transmissions. But diesel oil used as a motorcycle oil won’t necessarily provide good value. Even if it has a lower price tag.

Dedicated motorcycle oils have a precise base oil and additive package combination. This balance of ingredients delivers specific protective and performance characteristics. This chemistry will not be found in diesel motor oil.

The reason that diesel engine oils can be used in motorcycle engines is that they do not contain friction modifiers. The friction modifiers found in passenger car motor oils (for gasoline-powered car/truck engines) will quickly glaze wet-clutch plates.

Here are some of the features of AMSOIL Synthetic Motorcycle Oil that are not a consideration in the design of diesel engine oils.

Motorcycle Oil Vs. Diesel Engine Oil In Transmissions

The biggest knock on diesel engine oils in this case is that they are not formulated for motorcycle transmission use. When used in common sumps (for both engine and transmission), diesel oil can be prone to sheering down and losing viscosity. Some diesel engines have timing gears, but this is nothing like the concentrated thrashing of a motorcycle transmission. The meshing of gears in motorcycle transmissions can rapidly sheer down oils that are not equipped for that type of use. Therefore, this rapid thinning will also hurt the diesel oil’s ability to protect the engine in common sumps.

AMSOIL Synthetic Motorcycle Oils are loaded with ingredients that withstand heavy transmission use. AMSOIL is also famous for lowering transmission friction for buttery smooth shifting. This factor alone is well worth the step up to AMSOIL.

Wet-Clutch Performance And Longevity

Diesel oils may not cause clutch plate glazing, but they are not formulated with wet-clutch performance and preservation in mind. AMSOIL Synthetic Motorcycle Oils are formulated to fight clutch fade and provide consistent clutch “feel”. They deliver steady clutch performance under high heat and extreme loads. Dedicated motorcycle oils will maintain the correct frictional properties over long service intervals.

Motorcycle Engine Oil Withstands High RPM And Heat

High revving motorcycle engines can red-line anywhere from 5500 rpm to well north of 10,000 rpm. They can also generate extreme heat. AMSOIL Synthetic Motorcycle Oils withstand extended periods of high RPM and extreme heat. The low-friction formula provides cooler operating temps. AMSOIL has performed extensive testing to prove that their motorcycle oils can be exposed to long periods of extremely high heat (over 500°F!) and high RPM without breaking down.

AMSOIL Adds Anti-Rust Protection To Motorcycle Oil

When designing their synthetic motorcycle oils, AMSOIL borrowed anti-rust and corrosion technology from their Marine Engine Oils. Engine internals are protected from moisture ingestion and long periods of off-season storage. Diesel engine oils would not contain this level of anti-corrosion ingredients and would not be as effective at protecting engine parts from rust.

Service Interval: Some Motorcycle Oils Are Extended Drain Capable

AMSOIL designs their V-Twin and Metric Motorcycle Oils for long service intervals. They can stay in service for up to double the interval as suggested by the engine manufacturer. AMSOIL formulates these oils to withstand the heat, transmission gear thrashing, high RPM. They also have the capacity to hold clutch, transmission and combustion deposits in suspension over this interval. Diesel engines oils are not designed to provide this length of service. As mentioned, the meshing of gears in transmissions will quickly sheer down diesel motor oil and reduce its service life.


As we’ve shown, the formula for motorcycle oil is different from the chemistry required for diesel engines. Diesel engine oils are missing several key components. As a result, this can compromise wear control, performance and engine oil life. AMSOIL Synthetic Motorcycle Oils provides superior performance, better engine and transmission protection and longer service intervals.

Diesel engine oils like Shell Rotella may be cheap, but that’s about it. A good synthetic motorcycle oil like AMSOIL is about the most cost-effective upgrade one can make to a motorcycle.