i have aw32 in the hydralics of my cat excavator and i was told aw46 will mix with it ,
as i replaced some cylinders and need to top off.
is the okay? any adverse affects? is it true that the number is just viscosity? thanks

Yes, the number is the viscosity. What viscosity does the excavator call for? I would try to stick with the recommended viscosity. Mixing in a little of a slightly higher viscosity should not cause any problems though.

Hello, Feam.

I would like to add that it is NOT wise mix different brands of lubes, if you are going to mix an ISO VG 32 with an ISO VG 46, the lubes must be the same brand, altough rare, there is the chance that different brands cause problems due to incompatibilities in the additives.
Regarding viscosity increase, Mike has cleared better than i could.

Dear Feam,
Yes the numbers are the viscosity grades and in your case you are intenting to top up, and you can be sure that if the same brand and poduct type are mixed will not give any adverse reaction. even if you top up 50% of the capacity the viscosity would still be at around 38- 39 CST and should not be a problem.
Collins David

Thanks for info , it is is two different brands.
catterpillar brand is in there now i will top off (maybe 40% ) with local castrol .
Machine calls for varying viscosity for working temps so thats not a problem i never work in winter. Should i drain system and put all new? If i drain do i hve to clean with something?
its a 30 gal system. Thanks for all the help.