Lude Generation

So I've always put 10w40 semi in my lude and black wagon

But when I went to performanceautoworks last year Rich put 5w40 Fully in it.
I'm about to buy more for a oil change as its due.

whats the benefit of either?

5w is thinner when cold, than 10w.
That's the only difference in viscocity.
Honda recommend different viscocities depending on which climate (ambient temperature range) you are in. So you can use 5w, but 10w is actually the best overall match for the UK ambient range.

Fully synthetic is more aggressive in cleaning and can stand up to extreme use better. It's not normally a good idea to put fully synthetic in a high mileage engine that has been run on full mineral all its life. In your circumstance, fully or semi should be fine.

See here previous discussion on that and I posted up the Honda schedule for oil viscocities on the lude.

5w only becomes specified if ambient temps go below 20^C (and it doesn't offer 5w-40 at all as a recommended viscosity range, with 5w-30 only to be used in h22's if temps don't go above 0^C)

10w40 semi erection oil in used engine.

10w40 fully synth in rebuilt engines.

Aye