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Differential Oil Recommendations
Many RC cars today use oil filled diffs, and depending on the car there might be one, two, or three of these in a car. Differentials play an important role in a car, so it is therefore important to rebuild your diffs regularly. You can also gain a lot by adjusting the diff action by changing oil viscosity.
You can tune the drivetrain of your RC car to influence the way your car behaves when entering corners and rolling on idle. Keep in mind that regular maintenance and making sure the car functions mechanically as it should are even more important than tuning. Differences in suspension, wheel angles and poor movement of the suspension affect the car’s performance and eliminate the benefits gained with tuning.
Only after you’ve made sure that the chassis and the drivetrain are functioning correctly, you can start tuning the car the way you want. In this article, we’ll discuss differential oils and how they affect your car’s performance.
In RTR cars the diffs have a lubricant grease as default, with which basic steering capabilities are achieved for hobbyist purposes. The diff maintenance should be carried out 2–3 times during the season. In other words, check the condition of the diffs 1–2 months after the first runs of the season and replace the default grease with suitable differential oil. While doing this, also check the condition of the diff seals and replace them if necessary.
The oil’s viscosity will affect the car’s cornering capabilities at different points during cornering. The diff oils have a significant impact on your car’s performance.
For example, the basic set up for 1:10 4x4 buggy or short course we recommend is 5000 cSt in the front, 5000 cSt in the center and 3000 cSt in the rear. With this setup, you’ll achieve neutral behavior while cornering and during acceleration when exiting corners. The 5000 cSt oil is thin enough for the car to corner without throttle, but thick enough for steering during acceleration. The 5000 cSt oil in the center makes the car behave neutrally in mid-corner and at the end it allows the power transfer to the front wheels. The 3000 cSt oil is thin enough to allow easy cornering and thick enough for accelerating because it makes the other rear wheel retain traction.
If you want your car to accelerate a little faster when exiting corners and better cornering with throttle, we’d recommend 7000 cSt oil in the center diff. This will change the car’s behavior in mid-corner and when exiting corners.
When driving on high-traction surfaces such as mats, you can use thicker oils for the diffs, for example 7000 cSt in the front, 7000 or 10 000 cSt in the center and 3000 or 5000 cSt in the rear diff. The high-traction surface allows for the use of thicker oils.
That is just an example and basic guidelines for differential setup. Check from your car manual what oil is recommended for your car.
Effects of Differential Oil Adjustments:
Front Differential:
Using thinner oil:
- Increases steering into corners (off-power)
- If oil is too thin the steering may become inconsistent, especially it can lose forward traction (and steering) during acceleration out of corners
Using thicker oil:
- Increases stability into corners during braking
- Increases steering on-power at corner exit
Center Differential:
Using thinner oil:
- Front wheels unload more during acceleration
- Easier to drive on rough tracks
- If a high-power engine is used you could waste too much power and sometime “cook” the oil in the center differential because it “overloads”
- More off-power steering
Using thicker oil:
- Better acceleration
- Increases on-power steering (reduces understeer)
- Better suited on high-bite, smooth tracks
- Too thick oil gives more over steer
Rear Differential:
Using thinner oil:
- Increases cornering traction
- Increases steering into corner
Using thicker oil:
- Decreases rear traction while cornering
- Reduces wheelspin
EuroRC Team Recommendations:
For 2WD buggies and truck outdoor use 2000-10000 cSt oil. For indoor racing 10K is ok. High power brushless setups may benefit from thicker, up to 30K oils.
For 1:10 4WD Short Course trucks the basic set up we recommend is 5000 cSt in the front, 5000 cSt in the center and 3000 cSt in the rear.
For 1:8 Bashing trucks such as Corally or ARRMA, our team recommends 10000 cSt in the front, 7000 cSt in the center and 5000cSt in the rear. If you want just to pop wheelies use this setup: 15000 cSt Front, 15000cSt center and 10000cSt rear.
For crawlers: Use thick grease such as marine grease for crawler gears.
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