On my 71 BRE 510, the "Lifetime" warranty Koni Shocks failed a few years back.

Koni of America said those were from Holland or some crap like that.

Anyway, I found some stock 510 Struts and dropped in the 400cc [or whatever] amount of 80/90 Gear Dope.

Oddly enough, there was minimal difference, at slow speeds it was certainly rougher, but about 35+mpg it got normal, back to the factory .89g skidpad{or so it felt anyway}

A pal at a Kawasaki Dealer, says the Moto-X racers swap oil viscosity at minuscule viscosity increments to gain advantage.

Anyone else swap out from stock SAE 5w Hydraulic Oil ?
Or am I still in the 70's, and you all use unobtanium Oil today ?

Most are running cartridge insert shocks. Well some still have regular strut glands, but not any performance people as far as I know.

My friend in LA just bought new Konis glands last month (december). They are new old stock.

I've used Motorcycle fork oil in a set of b310 struts, I used 15w20, the other types I recall were 5w10 & 10w15. I only used about half the bottle to do the 2 struts. Was a cheap upgrade when inserts are over $100 each & getting hard to find. Makes them stiffer on compression, but rebound I can't remember, as it was done for a friends car.