The answer depends on what Chain Oiler you are using, where you live and seasonal variations, please read on.....
In brief..........If you have the TUTORO Auto you can use the standard TUTORO Chain oil all year round where the ambient temps are around 25°C in the summer.
BUT if the temperature starts hitting 29° or more then you should think about using a gear oil such as a Hypoid EP80/90 for the duration of such a hot spell.
If however you have a TUTORO Manual then you can use a Gear Oil EP80/90 all year round or the Standard TUTORO chain oil in the winter and a gear oil in the summer.
If you live somewhere where the ambient temperature is 25°C or above then you can use a Hypoid EP80/90 Gearbox Oil in either the TUTORO Auto or the TUTORO Manual chain oilers.
WARNING- NEVER USE AUTOMATIC TRANSMISSION FLUID otherwise known as ATF (more about this below)
Beware of using a Motor Oil which has a low "W" rating such as 5W-30........ 5W (where W means Winter) is designed to have a viscosity rating of only 5 (very very thin) when in a cold (read ambient) condition and a thicker 30 rating when at 100C, however in our application the oil will never reach 100C so the oil will never be thick enough to be useful.
As a guide we suggest that if you use a multigrade motor oil, whether its that old can you've had knocking around in the garage for years or an impulse purchase of the latest "Special Offer" Supermarket lube, make sure its at least 20w rated. Please bear in mind an engine oil does not have the same additives as our TUTORO chain oil.
There is an excellent article on motor oil and its viscosity here:
Our chain oil is made to order and has wear modifiers, anti-friction, anti-fling and steel coating additives - engine oils are designed to do a different job and I certainly wouldn't recommend using chain oil to lube your engine!.
What Oil should I use ?