Hi from the north country. I just bought a new suzuki c50 for my 60th birthday after not riding for 25+ years. this will most likely be my last bike and would to make it last. I starting reading up about all the new oils out there and and have found a lot of talk about folks using truck oil like rotella,delvac and others. I have been wading through a million pages of info but one thing is clear ,amsoil is what my local dearer sells but at over 11.00 a guart,(and my bike takes 4 and I like to change it every 1000 to 1500 miles) I'm starting to think ,maybe, this was a mistake to start riding again. In the old days castrol covered everything. Thanks for hearing me vent, But truck oil? Really? I can't afford another motor. the manual says 10-40 or 15-40 but says nothing about synthetic. I'm really confused about all this HELP!