This issue I’ve decided to discuss one of the most contentious topics about classic Indian motorcycles- and it’s not the correct shade of Indian Red!
OIL
Now everyone has an opinion about what oil to use in the motor. Here’s some things to make you think:
I’m not going to tell you which oil to use or which brand.
Probably most of us use a Monograde 50 weight oil.
Some of us use a filter either in the tank from IPE Kiwi, or an external filter like a Panhead Harley type. Then a detergent oil is ok as the small particles can be filtered out along with the metal particles that will be a product of wear and running in a newly rebuilt engine.
Realistically how many miles do you do a year? I must have done over 30,000 miles on the Chief in 15 years- 2,000 a year or 2 oil changes with an in tank filter. On my Scout total mileage is about 12,000 over 10 years, and most of us only ride in the better weather.
Our motors have roller bearings in the crank and main bearings, we also have no upper cylinder head oiling to worry about, so a Monograde 50 weight oil is ok for summer use. However it’s a seasonal oil and when people rode all year round they would change to a lighter viscosity weight oil on the winter like 30 weight/viscosity. In the winter I’ve had to light a camping stove under the sump to be able to start my Chief on 50 weight. But I’m talking below freezing temperatures and the bike left outside. For example VW Beetle air cooled engines used to recommend Castrol CRI 30w, and they only had a wire gauze sump filter.
You could consider a 20/50w oil like Valvoline VR1 which is recommended for air cooled V twins. One major advantage is the addition of ZDDP a zinc based anti-wear additive. Not normally found in modern oils as it’s likely to clog a catalytic converter.
Also excessive heat kills oil, it reduces the ability to stay in grade, if your motor gets very hot in summer traffic change the oil.
If you Indian is total loss oiling like the pre 1931 Scouts and Chiefs, sure 50 weight oil is fine, but I use 2 stroke oil in my 101 Scout as it’s designed to be burnt like any 2 stroke motor and it’s less likely to suffer from carbon build up in the combustion chambers. I’ve used it for 5 years now, and done as many miles as most of you, and had no problems. I did remove the oil control rings from the pistons to stop excessive oil build up in the crank cases which caused overheating.
As to your transmission, if you have a sealed primary you can use a 80w-140w modern gear oil, and a light oil in the primary chain case. Harley Davidson use something very similar to automatic transmission oil in the primary cases. Otherwise use a gear oil, for shared gearbox primary systems, remember gear oil viscosity rating is not the same as engine oil, so 90w is not like a heavy motor oil.
Like I said in the beginning, everyone has an opinion about oil. Just think about one thing, if you're low on oil on a long trip, and not much option as to which oil you can get, you would put anything available in rather than run low on oil!
Remember:
You always win with Indian Tim 
