Hi there,

I own a 1988 Dodge Ram Van B250 with an A998/A999 automatic transmission and an 8.25 differential. I recently topped up the oil in my differential with SAE 80w-90 GL5 as recommended by the Haynes manual but I recently went through the invoices from the previous owners and I see that the oil that was previously put is 75w140.

I wanted to know if there was a real problem and if I should drain the differential? I put back 0.75 l of 80w-90.

It seems to me that the 75w140 is synthetic and that the 80w-90 is mineral.

Thank you in advance for your return.

 

The two oils will mix just fine, no need to do a drain and replace.