Dexron 3 and Dexron 6 are popular automatic transmission fluids used in many vehicle’s transmissions to lubricate the moving parts. While both types are used on most transmissions, can you mix Dexron 3 With Dexron 6?
In most cases, you can mix Dexron 3 and Dexron 6, especially when adding small amounts to top up. It’s ideal to empty the old transmission fluid before adding this mixture. However, mixing should only be done on transmissions that use Dexron 3 since Dexron 6 is backward compatible.
I have discussed more on the possibility of mixing Dexron 3 and Dexron 6, including the potential risks. Read on to learn more, including how the two fluids compare.
Table of Contents
Can You Mix Dexron 3 and Dexron 6?
Yes, you can mix the two types of automatic transmission fluids without causing issues with the transmission.
For instance, when your transmission, which uses Dexron 3, is low and you have a Dexron 6, you can use it to refill. Dexron 6 is backward compatible, meaning it can work in transmissions that earlier Dexron ATFs can work on.
However, refrain from mixing Dexron 3 and Dexron 6 when dealing with newer transmissions designed for Dexron 6 fluid. The lower viscosity and boiling point of Dexron 3 ATF can affect the transmission performance.
But if you’re only topping Dexron 6 with Dexron 3, use the least amount possible.
Also, I recommend you first drain the old transmission fluid before adding the mixture of the two. And change the transmission pan magnet. If you forgot to put magnet in the transmission pan, stick it outside or drain the fluid again.
Factors That Affect The Ability To Mix Dexron 3 and Dexron 6
While you can mix the two types of automatic transmission fluids, there are various factors to consider. These factors contribute to the ability to mix Dexron 3 and Dexron 6. I have discussed these factors below.
1. Compatibility
While the two types of Dexron ATF oils are oil-based, they differ slightly in formulation. The Dexron 3 is semi-synthetic while the Dexron 6 is a fully synthetic lubricant.
Both formulations give better wear protection and since both are synthetic, mixing them is easier. However, each is made to suit a specific type of transmission, and mixing both may result in less effective transmission fluid.
2. Viscosity
Dexron 3 is more viscous than Dexron 6 transmission fluid. Lower viscosity means the fluid flows easily through the gears, lubricating them. This better fluidity is among the reasons I prefer Dexron 6 ATF.
The difference in viscosity means mixing them you will make a less viscous (Dexron 3) or more viscous (Dexron 6) fluid. Depending on the transmission you are using the mixture on, this can positively or negatively impact the performance.
3. Mileage and Service Frequency
By the word mileage, I mean how long the fluid can run before it needs a complete change and flush. Dexron 6 lasts longer (between 100,000 and 200,000 miles) and doesn’t require to be frequently changed.
On the other hand, by 80,000 miles Dexron 3 fluid needs to be replaced and flushed. When you mix the two fluids you reduce or increase the fluid mileage depending on the transmission you’re using it on.
Also, you will need to check and change the transmission fluid more frequently than usual. Personally, I prefer to check and change transmission fluid after 30,000 miles, which professionals also advise.
4. Suitable Temperature
Both transmissions differ in the preferred operating temperature. Dexron 3 suits colder locations, while Dexron 6 suits warmer temperatures. Dexron 6 suits warmer locations due to the higher boiling point and flash point.
However, Dexron 6’s lower pourpoint makes it suitable for use in cold weather areas. Therefore, mixing the two will make a fluid that works in warm and cold temperatures.
5. Manufacturer’s Recommendations
Dexron is a name of various specifications of automatic transmission fluid by General Motor. General Motors says that Dexron 6 can be used in a transmission that uses Dexron 3.
So, as per manufacturers, mixing the two-transmission fluid should not be an issue. However, this is as long as the mixed transmission fluid is used on earlier transmissions that use Dexron 3. Car transmission using Dexron 6 will have issues using the mixture of the two Dexron fluids.
To avoid issues, use the transmission fluid that the manufacturers recommend.
Potential Risks Of Mixing Dexron 3 and Dexron 6
While mixing the two types of Dexron transmission fluids is feasible, there are potential risks. Mixing the two poses a risk since the two ATFs have differences I have discussed earlier. The following list contains these potential risks.
1. Reduced Transmission Performance
The difference in viscosity and formulation in the two fluids can reduce the transmission’s performance. The more viscous Dexron 3 means the fluid flows slower through the gears in the car’s transmission. These factors can reduce the transmission’s performance.
2. Lower Heat Resistance
Mixing Dexron 3 and Dexron 6 lowers the ATF stability at high temperatures since in Dexron 3, it’s lower. Instability at high temperatures means the transmission is more likely to lose its effectiveness and break down.
3. Inadequate Protection
Mixing the two also means reduced protection against friction and wear. The lower viscosity in the Dexron 6 can cause reduced protection on old transmissions designed to use Dexron 3.
You may also notice a reduced performance when the vehicle shifts and experiences slippage.
4. Obstructed Fluid Flow
In rare occurrences, the formulation between the two transmission fluids may cause chemical incompatibility. When the fluids are incompatible, they can form sludge or deposits in the transmission, obstructing fluid flow. This occurrence will negatively affect the transmission operations.
People Also Ask
If you still have concerns regarding mixing Dexron 3 and Dexron 6, here are meaningful questions that most people ask.
Should I Flush A Transmission Using Dexron 3 Before Adding Dexron 6?
Flushing the transmission is unnecessary when adding Dexron 6 instead of Dexron 3. In most cases, emptying the Dexron 3 transmission fluid before adding Dexron 6 is enough. However, a flush will be necessary if the old fluid is too dirty.
What Should I Do If I Added Dexron 3 Instead Of Dexron 6 in The Transmission?
If you mistakenly added Dexron 3 instead of Dexron 6 on your car’s transmission that uses Dexron 6, you must empty it. Car transmissions designed to use Dexron 6 will not work with Dexron 3. Get the correct fluid and add it.
Is Dexron 6 Compatible With All Transmissions That Use Dexron ATFs?
Dexron 6 ATF is not compatible with all transmissions that use these ATFs. Newer transmission types that use Dexron HP or Dexron ULV will have issues using Dexron 6. Always use the manufacturer-recommended Dexron ATF.
Final Words
To conclude on this topic, yes, you can mix Dexron 3 and Dexron 6. However, the mixture works better on older transmissions designed to use Dexron 3. Using the two types in newer car transmissions that use Dexron 6 may result in issues.
I recommend you stick to the transmission fluid your car’s manufacturers suggest you use and only mix the two where necessary. The differences in viscosity, boiling points, formulation, and suitable temperatures can affect the transmission, resulting in problems.
