Modern Vespa

Book says 80w-90 GL3 or above I think, bought some Castrol synthetic75w-90 GL5 does it matter? Haven't opened it and can return it. What's the GL mean anyway? Thanks in advance for the good advice here.

Gl3 was then and now its gl4,gl5, it has to do with what's in it and safe for different alloys.Like rust inhibitors I guess.So what you have is fine.

Good to know, thanks.

Gear lube?

Haha might be . I've read some in depth threads here about 3,4&5 and don't remember much lol So I'm using royal purple gl4/5.yah some have both,but what I understand is anything will be ok 4,5,4/5.. It's gona be a long long long time till I change it again.

Ya, that's the way I read it, too..... that GL4/5 is an improvement over the GL 3 spec. That and the fact that GL 3 seems harder to come by these days....

I'm using the Valvoline 75W/90 synthetic. I believe I've read here before that even mineral oil (non-synthetic) can be used in the hub oil but I like the synthetic stuff cause it almost always has better properties (sheer, temp, etc.).... Costs more, that's all...

Good, and I've read here or somewhere that it's all the same as 30W. Don't want to try that though.