CHEVROLET 1999 Corvette - Manual (Page 263)

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NOTICE:
Don’t add too much oil. If your engine has so
much oil that the oil level gets above the upper
mark that shows the proper operating range,
your engine could be damaged.
The engine oil fill cap is on
top of the passenger’s side
valve cover.
Be sure to fill it enough to put the level somewhere in
the proper operating range. Push the dipstick all the way
back in when you’re through.
What Kind of Engine Oil to Use
Look for two things:
D GM4718M
The Corvette engine requires a special oil meeting
GM Standard GM4718M. Oils meeting this Standard
may be identified as synthetic. However, not all
synthetic oils will meet this GM Standard. You
should look for and use only an oil that meets GM
Standard GM4718M.
NOTICE:
If you use oils that don’t have the GM4718M
Standard designation, you can cause engine
damage not covered by your warranty.