Has anyone been using any other brand of coolant other than BMW high priced rip off brand?
BMW don't make coolant and charges a hefty price to put there name on some. I know of people who use Prestone coolant and had no problems.

I've been using the local no-name brand from the wee shop up the road and never had any problems. We stuff it in the car too. Ethylene glycol is just ethylene glycol, however you package it. Just be sure to use distilled water to stop clogging up the system with limestone/peat/add your local groundwater contaminant here.

I use the green Nulon, that is a brand name, but any of the brand name are good.

I use Engine Ice. 
A bit pricey but it addressed what I was looking for, namely cooler idling/city riding. Markedly effective.

I have been using the standard local antifreeze, branded Partmaster (an auto parts supply chain). No problems.

Remember that what these K bike motors are is essentially a shrunken version of a car engine flipped on it's side and chucked in to a motorcycle frame with not a lot of difference mechanically as far as cooling requirements are concerned

In fact they probably run a fair bit cooler than a car version with the exposure to the rushing air and a lot less weight to push around than a car

I don't over think things as far as this model of bike goes

I use normal antifreeze, Ryco Z418 oil filters instead of the beema expensive ones and a higher detergent diesel engine oil just as a precaution to perhaps slow down the sludge buildup that affects the starter clutch

Dai wrote:I've been using the local no-name brand from the wee shop up the road and never had any problems. We stuff it in the car too. Ethylene glycol is just ethylene glycol, however you package it. Just be sure to use distilled water to stop clogging up the system with limestone/peat/add your local groundwater contaminant here.

 Yep, any brand or generic will do the trick. I buy 50/50 and call it good. I could care less about the brand on the container. I think I last purchased O'Reilly's auto store self labeled anti freeze here in the states. It is a little less expensive and probably made by Prestone or some other major brand.

The best anti freeze is pure water. Add anything else and it becomes less thermally efficient. You need to use anti freeze because it is also corrosion inhibitor and antifreeze. The coolant does not give a monkeys whether it is in a car or a bike, but the K engine has nothing to do with any car engine.
Better to let the engine run at the correct operating temperature so anyone who tells you that a coolant can cool better than water is talking rubbish. Why would you want it to run cooler, you will only damage the engine if you don't get it up to operating temperature every time you ride it.