Those "rubber looking caps" in the valve cover are the spark plug wire boots. At the bottom of the hole is the spark plug. The oil you refer to is engine oil.
At the end of your dipstick female part (part that stays in engine when you chkng the oil) you have a small rubber seal.
Auto trans, dipstick located at left rear of engine compartment, under the brake master cylinder, buried under one or more rubber heater hoses. Manual trans, dipstick is larger, and located on right side (passenger side) of engine compartment, behind engine, about halfway between rear edge of engine and the firewall.
Cut the tube with a tubing cutter- remove dipstick and use rubber tubing and hose clamps to reassemble dipstick tube what up.
lube the end of the dipstick and use a rubber hammer and pound it down into the oil pan.
With the engine running and warmed up all the way you should see the dipstick located on the right hand side of the engine in the back ( same side as the oil dipstick). It should have a black rubber top on it. Just pull it all the way out wipe it off put it back in then pull it back out to read what the level is.
On the 2.2 engine, it's on the front of the block behind and just to the right (when looking at engine from the front) of the oil dipstick tube. Look for an orange rubber cap on it, and a 3-wire cord that'll be wrapped up not to far from it.
Northstar engine huh? Look towards the drivers side below the big rubber hose from the air cleaner. You should see a red plastic screw cap. This is the transmission vent. Unscrew it. If your car has a transmission dipstick, and many northstars don't, it is built into the vent cap.
Cut the dipstick tube with a tubing cutter below broken dipstick and remove Use rubber tubing and hose clamps to reattach tube pieces
Mine was black rubber coated, located drivers side engine compartment, behind the engine, under tubes/wires, close to the firewall, about a foot down, below the black (plastic) covering below the windshield.
If your looking at your engine from the hood opening it on the left side right next to the oil dip stick and it should have a little metal tag or have a red rubber coating on the pull ring.
inside the rv, lift up the panel, it's a small dipstick hiding on the passenger side on the top. Mine had a rubber boot on it hiding the dipstick very well actually.
Its a little hard to see at first , but its right behind the engine at the left side , there will be a rubber dust cap first , remove that and you will se the rotating cap the has the built in dipstick on it