Please read to the end before jumping to a conclusion !!!!
I was always under the impression that Car oils and Bike oils were different, the main being friction modifiers added to Car oil..
Another point being "Engine Oil" which is fine in a car, truck, whatever, but in a bike, it it also the gearbox oil. cars use hypoid gear oil, something you wouldn't put in an engine.. So oil for a bike has to be able to stand up to gearbox use...
Then there's the wet clutch, again, something cars don't have, so an oil for a bike has to suitable for wet clutches..
There has been cases of clutch slippage when using full synthetic car oils.
Now, even though all the above seems to make sense, I have heard of many people recommending nothing more than regular car oil, having used it for years with no problems..
Oil has only 2 main functions.. 1/ to lubricate. 2/ to aid cooling. Any oil worth it's salt will perform both of these without question.
The main thing to note is the viscosity of the oil being used... too thin, and it won't lubricate properly, too thick, and it won't flow, and create too much friction. always check the handbook for the correct grade for your area. Cold climates use thinner oil than Hot climates.
Whether you want to use Bike oil or Car oil is your choice, neither will cause any damage so long as the correct grade is used, normally 10W/40.
The only thing that may have concern is the wet clutch, and if you do get any slippage, just change the oil.
If as Wally says, Heron Suzuki always recommended GTX, then that's good enough for me..
As a comparison, I drive a Lexus GS300, and for the transmission, The handbook, and workshop manual states that ONLY Toyota T-1V fluid is to be used........ So can you tell me why the Lexus dealers always use cheap Dexron fluid... Profit and all that..
John