20W 50 is to heavy and makes your bike run hotter,go to 10W40,also running at higher speeds also tends to use more oil.

Hay I have a 1989 LS400 Iv'e dun 2000km since the last oil change and iv'e only just topped up the oil today for the first time
I ride at or over 100kmph every day for round 5-10 min and round 300km distance every week

I'd look into the oil you are using and for any leeks, it shouldn't be going through it that fast

An interesting read about viscosity and temperature.

https://www.motorstate.com/oilviscosity.htm

here 's a the poop on oil, oil flow is what lubes your motor and carries the heat away!the first num. before the W is the weight (viscosity) of the oil at an operating temp of 212 degrees .(car operating temp)the second num is level the oil is based on. the temps our air cooled motors run at tends to thin the oil (270to300 degrees) a 10W oil drops to 8-9 w,a 20w to about 15-16w ,The thin oil 10 w flows easier ,provides a thicker film between parts (due to it higher flow volume) and carries away more heat for the same reason.20 w oil being thicker provides higher oil pressure ,but doesn't get the job done!The bike runs hotter!On the hottest day of the year at the highest speeds the 10W40 is a better choise than a 20W 50.     OIL only gets thicker as it cools! 10W 40 has a viscosity of about 150 at 75 degrees 20W50 is at about 250 at 75 ,due to the second num the oil there based on.This is the reason 90% of engine wear occurs at startup (where no oil is thin enough to provide proper lubrication ) but the lighter oil will warm faster.that is one of the reasons auto makers are going to 5W30 ,5W 20 .this holds true for dino based oils.........synthetic oil is a bit different a15W 40 oil of this type is based on 15W "oil" which drops to a viscosity of about 12.5 at our operating temp. An additive package keeps it there about twice as long,and is why it doesn't have to be changed as often.IN fact if you could buy the package and put it in your oil it would never have to changed at all. The other advantage of a synthetic is as it cools to 75 degrees the viscosity is only about100w,which is still to high to lube the bike but warms much faster, reducing wear at startup.......Bottom line,  use the oil of your choise,but don't think a 20w50oil is going to do a better job than a 15w40 or a 10W40....both oils thicken with age,dino oil builds up wax(paraffins), and the additive package wears out in synthetics.

manbat... you're ass backwards.

Quote:


don't confuse "w" with weight, in 5w-40, it stands for winter, a temp like -15°C or some BS like that.
the second number is the weight at normal op temp like 212°F

I run Rotella Dino, and change it when one of the following happens.

1. 3000 miles
2. Transmission shifts hard (oil breaking down)
3. Gas in oil (repeated short trips in winter)

1 and 2 usually happen about the same time.