If you have driven the car, change the oil each month.
The premise for this is that Oil is actually the heart and soul of an air cooled engine. It not only contains the lubricant but it also cleans the system and removes the fine metal debris that any engine creates.
Since it (the engine) is small and it runs at a high level of heat and speed, this little stuff can quickly age your engine so, the extra $40 a year in the additional oil change is VERY cheap insurance (especially since there is no real oil filter on a stock VW.
So.. that's MY take on oil changes.
Your noise may not be oil.. it sounds more like engine knock. Check your timing or your distributor advance.
.How to figure out its time to change engine oil ?Well there will be a dip stick(check around the engine or refer an online manual for that) and follow these steps
#1 turn of your engine, wait for 1 minute
#2 pull the dip stick and wipe it clean with a clean cloth
#3 now insert the dip stick again, and pull it out
#4 identity till where the oil is present on the stick
#5 if you observe that dip stick, you will find 2 holes on it(the hole nearer to your hand in which you are holding the stick) is the OK limit of your oil. the other hole(farther from your hand) is the minimum limit, if oil level is below this you need to refill your oil immediately to avoid any engine damage
and regarding your problem at high speeds,may be the piston head is hitting the values which gives that sound or it can be the rumbling sound due to lack of oil, check you oil level and if it is OK and still the sounds persist then you need to tune your engine.
If your are lucky enough it can be solved by changing the oil.How to figure out its time to change engine oil ?How many miles since the last oil change? Thank goodness 69 Bugs are easy to repair.
