1990 RM250 advice

cant tell ya the scientificals but I owned an 88 cr250 and ran golden spectro for a couple seasons, honda hp2 for a couple, castor 927, amongst others. the only problem i ever had is when I used the 927. it was when i ran out of fuel and used my cousins. same ratio but i was misfiring so bad i think it caused my seal to blow out. when i disassembled the clutch all i had to do was push the seal back in. I would stick my neck out and say pick a reputable widely available brand, price and smell you prefer and stick with it, youll be fine

I've been using Motorex 2t oil in my bikes for the last 10 years, and have never had any problems. It is synthetic.

Go with Ipone, on race day thats all you can smell when the 85's are on the track. (smells like strawberries :cool: )