Too Much Oil in the Engine – Can it Damage Your Car?

Let me take you back to my teen years when I had to take care of my daily driver and my Dad’s daily driver/working car (I would eventually get it as he upgraded, of course). One night my dad got home from his job as an on-the-road salesman and told me:

“The Mercury is running a bit warm, can you check?”

I said sure and proceeded to head out with the keys where I popped the hood and then I ducked inside to start it up. Within a moment, the temp gauge buried itself with the H(ot) of things. I looked at the oil pressure (this was the 60s and most cars with decent engines had oil gauges. The gauge sat right on the bottom bump stop.

I looked at the dipstick and it was bone dry. Suffice to say, I took another one of our cars (we had three at that time, one wasn’t running) and I ran to a buddies gas station where I purchase 5 quarts of 5W-30 and poured in 4. The dipstick read low so I added the fifth and everything was fine.

Now, if I had added a sixth to be sure or for whatever reason, it would have been wrong. Dad drove this vehicle for another nearly 60,000 miles before I inherited it. I gave up the ghost with more than 100,000 on the clock. The reason we dumped it was simple, the tranny was gone and we didn’t feel like investing anything in the vehicle.

With that said, let’s come back to today and go to your question and the answer is yes, too much oil can harm your car’s engine. Why is this so? It is simple, your car’s engine is made to run with a certain internal pressure that is at equilibrium as you drive. It’s not too high or too low.

If you add an extra quart of oil to the engine, it throws things way out of what. The increased pressure can easily harm various delicate parts because of the increased pressure. For instance, let’s take an engine oil gallery (it is like a capillary in your hand or foot or elsewhere). The galleries surround the engine doing double duty as they carry away excess engine heat while, at the same time, lubricating the engine. These oil channels, if you will, are meant to run at a certain pressure. Now, if you increase that pressure by lets say 3 or 4 psi, things start literally flying through the internals. Now imagine if a huge deposit breaks loose (like an ice flow) and it cruises along the galleries until it finds a gallery too small.

At this time, the oversized deposit blocks that gallery and in a reverse cascade, it starts to block up galleries all the way back to the engine intake. At this time, the blockage takes on even more significance because you can’t find it easily and it must be cleared.

In this case, it is possible that you will have to have the engine drained so you can clear this. Once it is drained and ready, you’ll need to have the galleries run to clean things up.

Honestly, it is too big a job for a casual driver; a mechanic has to strip the engine down and clean things out when he has access. When he has finished, he has to reinstall the various pieces to get your engine running. Usually, the parts are new and it will cost somewhere around $2,500 to take care of the work.