I've always heard that adding to much oil will cause problems so I have always been careful in that regard. A few days ago a friend asked me what kind of problems it would cause and I had to say "I don't really know". I just considered it a fact and never questioned it.

So, now I'm asking.
What kind of problems come with overfilling the crankcase?

 

If it's filled to the point that it touches the crankshaft throws, the oil can be whipped and aerated into a foam that can cause loss of oil pressure.

 

Pete,

A "friend asked"........

Do you have a guilty secret to confess here about your recent XJS maintenance?

Recommended oil capacity is a compromise between the overfill extreme Mike has described and the opposite where the pump draws air because the level is too low. A really serious overfill could cause hydraulic lock as the pistons are on the downstroke against an incompressible fluid level.

Graham

 

Not that I personally did this, but I know someone that did this very thing. This happened to a 79 Dodge Colt. The oil light came on and due to it being a recent oil change, the oil was hard to see on the stick (no light was available). So, a quart of oil was added to the engine and the oil light went out. Shortly there after, the oil light came back on. Figuring that the oil was really low, an additional quart of oil was added. Again, the oil light went out. Shortly thereafter, the oil light came on yet once again. The driver then said "@#$%^ it" and added in 4 more quarts of oil. The motor ran fine and was driven down the road. The driver then noticed that the streetlights he could see seemed to be flicking on and off. That was when it was realized that the motor was burning a ton of oil (due to be over filled) and was blowing tons of black smoke out the back. The car was driven another 40 miles (to get it back home) at which point almost 10 quarts of oil was drained out of a motor that only took 4.5 quarts to be completely full. Upon the refill, all ran fine.

So, yes, the car's mileage dropped like a rock. But, long term, can't say anything else was caused. So, going a quart or two over in most engines I don't think will cause anything significant to happen. Do I recommend doing that. Not really. But, this is just one case where things got taken out of control and all was good in the end other than a slightly lighter wallet.

 

Ha! Actually, we were talking and he was surprised when he saw me grabbing the second 5 qt. container and warned me about overfilling. He's an old American car guy and never uses more than 5 qts. for a change. That got us started on the "what if" discussion.

Thanks to all for the responses. I had to look up "hydraulic lock". Sounds pretty nasty.

pete

 

Pete, hydraulic lock is one of those things that if you experience it, you will know. If you think you may have, then you didn't. It is a very obvious thing when it happens, especially when things are moving and they suddenly come to a stop.

 

Hydraulic lock from an overfilled crankcase is very unlikely to happen on a multi-cylinder engine. As one piston descends, another is rising. The net volume inside the crankcase remains virtually constant.

 

Hydraulic lock is most often a result of one or more cylinders becoming filled with a fluid, often coolant, but could be fuel, or even water if the engine is submerged. The fluid can not be compressed, so with the valves closed the piston can not rise.

 

...most of the posts here are correct but it will increase presure on gaskets, seals and o-rings. Inversely, for being 1 quart low increases the engine temp by about 500 degrees F.

 

Gross overfilling can cause oil foaming as noted above.

However, slight overfilling will cause no damage and has been specified by Jaguar in the past.

Search for the discussion on the oil level specification on the Silverstone special edition.

In short, Jaguar specified 1 liter above the full mark on the Silverstone edition. It is thought that this recommendation was made to combat oil starvation in cornering.

To implement that recommendation, make sure you are using the right dipstick. The factory has issued two different dipsticks for the 4.0L engines. The later dipstick has the full mark 1 liter above the earlier dipstick. The 1 liter additional is specified as against the later dipstick, so 2 liters above the earlier dipstick.

I run the Silverstone specification without ill effect.

++

 

I am looking for an answer to a burnt oil or fuel smell in the cabin. Seams to be stronger when the cabin heater is on. Any advise?

 

It's an inline six so I'll defer to those with direct experience.

BTW, the Silverstone thing is in relation to the V8 4.0L not the six.

 

SteveByz, when you run the heat-A/C, you are pulling in air from the engine bay (unless on recirc). So, if you have any sort of burning oil smell being produced in the engine bay, you will smell it inside the car. With that being said, it can be something as simple as you spilled a little bit of oil when adding some and it happen to run down and touch the header. You could possibly have a small oil leak from a valve cover that is dripping down on to the header. If we are talking about an X-Type, it could be simply that you overfilled the transfer case and it is now leaking down on the exhaust header. If you can tell us the year and model car we are talking about, we can give you more detailed possibilities of what you are experiencing as we know most of the common issues that these cars suffer.

 

To make mayonnaise, use cooking oil, & some seasonings and blend till done. Overfilling an engines crankcase where the oil makes contact with the crankshaft at high speed will make black mayo. I seen this done on a small diesel powered water pump that ran for long extended periods. The oil pump could not pump the black mayo that eventually formed, and the engine wore itself out and seized. I know a lot of lawn mower engines use splash lubrication, but they use a small dipper for that purpose. Not the crankshaft itself. Another case where little is good and a lot is not.