Lube Mixing

This is a bit of a hot potato,
for us we would get the MSDS on both lubricants and toss thenm in the lap of the gasket/seal supplier and ask him the ensure compatability,

Rob S

Generally speaking most of the critical seals are of the synthetic type Viton or Neoprene and not affected by hydraocarbons or lubricants. When it comes to synthetics it is a different type of ball game altogether, as many of these synthetic products are no longer truly speaking hydrocarbons. They could be petroleum by-products or even glycols, polyglycols, Phosphate esters and so on.

It is best if tested individually. Simple layman tests could be done on site by immersing the relevant seals in the "oil" in a glass container and observing change over 4 to 5 weeks. Usually "seal swell tests" are conducted for most brake fluids as indicated above.

Much of the damage actually occurs in the presence of water or moisture.

Hussam Adeni

Sorry for the late reply.

There is nothing like a Iso Grade 55. It might be 46 or 68, otherwise it might refer to the viscosity at 40 C.

If both are Alkylbenzenes there is a high probability for them to be miscible and compatible and not react chemically. If you had gaskets compatible with alkylbenzene, there is no risk for the gaskets. The only risk I see is the use of the lower viscosity; However, if it was just a top up, there is little chance of a big problem.
Worst problem is that a mixing might happen to you again in a more challenging case.