Amsoil ISO vs SAE weight ratings

[Craig in Canada]

There isn't another perfect place for this, so I thought I'd put it here for starters.

I was ordering a couple of products from Amsoil (my first Amsoil purchases) and I noticed something odd. I was shopping for compressor oil for my air compressor which calls for ISO100/SAE30 and a possible high quality non-detergent SAE30 for pressure washer pump. It seems that all Amsoil applications quote ISO ratings that are "one grade off" from every reference I see elsewhere in the industry. Their PCK claims "ISO100/SAE40", PCJ "ISO60/SAE30", "ISO150/SAE50" etc... Everywhere else I've seen ISO100=SAE30, ISO150=SAE40, ISO68=SAE20.

Why is Amsoil the only company with this discrepancy? Various other google searches show lots of references to ISO100 being SAE30.

 

[Pablo]

I believe this belongs in “Heavy and Industrial Lubrication”, "Heavy Equip. and Industrial Oils"
The difference is that SAE rating ranges (from engine oils) are approximations of 100°C viscosity and are for ball park use only. ISO viscosity ratings are at 40°C, and are what Amsoil uses. Check this out:

http://www.amsoil.com/products/industrial/whitepaper7.pdf

 

[wgtoys]

For gear oils the 40 degree C number is probably much closer to typical use conditions than 100 deg. C. All this implies is that Amsoil's lubes have a shallower viscosity vs. temperature curve than do conventional oils, which is what one expects of a good synthetic. I would choose products based on the ISO number for an air compressor or pressure washer pump.

 

[Craig in Canada]

Ahhhh.

So, because 'most' compressor lubes are conventional there's a larger viscosity change between 40C and 100C.

Makes sense. I just hope the PCK I have on order for my ISO100/SAE30 compressor isn't too heavy.

Thanks,
Craig.

 

[Don Stefanik]

Criag.
Over the years I have sold cases and cases of the PCK for compressors that call for sae30.
No ill effects.
If on the other hand your compressor is outside then for the winter months you may want to use the AMSOIL ATF. It has worked out well in those applications.

 

[Craig in Canada]

Don: wouldn't the ATF have lots of detergents etc... which the compressor manufacturers are trying to get you to avoid? Why not a reduction to ISO68 or another thinner PC oil for colder months.

It so happens that my wee compressor does spend a fair bit of time in the cold and doesn't get used heavily, meaning it doesn't warm itself up well even when in use.

 

[Don Stefanik]

As far as detergents I don't think that is a problem.
I'm not too sure just how much detergent is in our ATF. It was AMSOIL who suggetsted the ATF to me for out side applications.
I also had a customer who used ATF for years in their Rotary Screw compressor with no ill effect.
I believe what the compressor companies want is for the oil to be able to mix with any water that get's into the crankcase. After all a compressor get's very hot and then cools down making condinsation in the tank.

 

[bruce381]

compressors depending on type have problems with ANY ash forming deposits so normally a NON metalic or NON ash oil is needed that is why non detergent is recomended.

Also
ISO VG grade is taken at 40C
motor oil are run a 100C
so with a high VI oil like amsoil you could have a ISO @ 40C of say 100 and a SAE @ 100C of a 40 because of the dif temps thay are tested at and the effect of a higher than "normal 95 VI".
bruce

 

[Craig in Canada]

FYI, stuck with the Amsoil PCK (ISO100). The explanation for the discrepancy makes perfect sense once I heard it from someone else

Thanks to all who replied.

Craig.