L and H?!?!?!? Is this the thing on the left under the hood or right where the driver sits? Almost sounds like the automatic tranny fluid vs engine. Usually trannys have a low and high warm and hot, etc.
Do what ever the manual for your car says.
"CHECKING ENGINE OIL LEVEL
1. Park the vehicle on a level surface and apply
the parking brake.
2. Start the engine and let it idle until it reaches
3. Turn off the engine. Wait more than 10
minutes for the oil to drain back into
the oil pan.
4. Remove the dipstick and wipe it clean. Reinsert
it all the way.
5. Remove the dipstick again and check the oil
level. It should be between the H (High) and
L (Low) marks 1 . This is the normal operating
oil level range. If the oil level is below
the L (Low) mark 2 , remove the oil filler cap
and pour recommended oil through the
opening. Do not overfill 3 .
6. Recheck oil level with the dipstick."