I'm of the opinion that changing the engine oil every 2000 - 3000 km's (1240 - 1860 miles) is a waste of perfectly good serviceable oil, especially so if you're using a high quality, full synthetic oil. An interval of 3500 - 4500 miles (5600 - 7200 km's) would seem more reasonable for those who put on a lot of miles per year. .
Actually its not .
i am engineer i talk based on tested results.
i have friend who is motorcycle mechanic and sometimes i repair / revive bikes with him.
When you change your oil every 2k-3k internal of your engine becomes super clean that increases engine life about % 15 -% 20. when you multiply % 20 with the cost of replacing your engine ( go ask your car mechanic how much it would cost) and by % 10 of your engine replacement cost you can afford easily 2k-3k oil change. Even you do it with cheap oils your engine becomes cleaner and when you went to breakdown to replace engine parts ,you simply replace far less parts and actually save money.
Only hinderance is that you have to change your oil frequently which is extra effort and time .
i change the oil and filter of my bike myself. if you are doing same you can also buy oil from direct distributor with big quantity for cheaper price.
Tip: same occurance also apply to cars. if you replace your oil by %25 km of the suggested amount you save engine life and part.
All manufacturers are same ; they all tell you "sufficent "or"average" care maintenance for your belongings. No manufacturer wants a bike ,car ,fridge ,shaver ect to last forever they just want you to buy again of same item in couple year(because they are all capitalist). When you can open inside of what they produce and sale to you and able to take countermeasures for their "planned obsolence" (go check that term what it means its a very long article) your property will last longer with less cost.
for example : to improve life of the sockets i sokaed all of them with wd 40 and covered with electric insulation tape. which will cover them with oil firm delay / inhibit oxidation and cover against water . so no more socket replacement issues for me nor short circuit issues. This trick is not even written in service manual.
as conclusion i suggest no one to replace oil every 8000 miles (oh my god you will kill your engine seriously and how come it writes 8000 miles in your user manual ? mine says 8000 km.) if you just dont want to bother with frequent oil replacement 5000 kilo meter should be your max out limit. Also as maximum every 10k you should change your oil filter.
side story:well ...according to my mechanic friend he actually poured salt instead of oil into hondacbr250r and run for 2000km . As he told me this bike(cbr250r) will even run with salt instead of oil .... ofc i did not tried myself
i hope this information will be useful for you. Also make your own research about it . Check with real results. Make calculations and see how it would be. According to my calculations in my country it will be beneficial. ( i dont know about your country. if oil costs alot and engine parts are cheap it might be useless for you its like chain maintenance vs chain replacement issue)