Winibald,

The YS will not run well on 10%-15% nitro; power, idle and response will suffer. It is even likely to overheat.
If this 10%-15% nitro fuel contains Castor oil, it will also clog up its pump. Only all synthetic oil for YS.

Dean,

Irvines may need 10%, or less nitro and could overheat from any more. They actually run very well (better) on 0-5% nitro.

Bob, Warren, Dean,

For the OS, GMS and Irvine, fuel containing some Castor oil is recommended; I believe all synthetic will void the warranty on OS engines. Although the GMS manual is inconclusive, ALL engine experts (Clarence Lee, David Gierke, Harry Higley, the late George Aldrich) said that in ABC/AAC/ABN engines, the fuel MUST contain some Castor oil (5%).
The YS 20/20 doesn't fit the bill.

Dean,

You will have to carry more than one jug, if you plan on having all your engines for a long time. Sorry.
Not too much of a hassle for your car, is it?

The Saito is the least of your problems, as it will accept any drink.