"The correct amount of oil" on the dipstick could be anywhere in the "full" range on the dipstick. If your oil level is all the way to the top of the "full" range on the dipstick, then if I were you I'd crack open the oil drain plug just enough that you can drain however many ounces of oil you plan to add of Restore into something that allows you to measure the amount of oil you've drained.

If the oil on the dipstick is halfway up the "full" range or below, there's no need to drain any of the oil out because halfway up the range on the dipstick means there's approximately 1/2 a quart of capacity remaining and the Restore you're adding isn't a 1/2 quart's worth of fluid.

Do NOT add any additives to your Civic. Period. Use the correct oil only.

LISTEN TO Stpaulguy.

use lucas not the restore

i got a 4cyl manual civic . 1.5L and was wondering. i have the correct amount of oil in using sythetic blend. and will adding a full can of this restorer ruin the engine because of the oil level? it says just add to engine oil . can someone help plz ty