Why Is Overfilling Oil “Bad”?

[DaniBoy]

I have read that “overfilling” the oil, especially on the 998 is bad. I don’t understand why it would be so critical when these bikes are a dry sump system. In my feeble mind, it would seem that in a dry sump, the engine will only draw the amount of oil from the reservoir that it needs, and it circulates through the motor/transmission and back into the reservoir. How much over is too much? 8 oz? A pint? A quart?

 

[Albec]

In some cases, overfilling can result in some moving engine parts being somewhat submerged in oil when they shouldn't be. While these moving parts are submerged, they can create an oil/air foam that can cause issues with the oil pump. Bad things can happen when the oil pump has an issue suppling oil to the engine, very bad.

 

[BajaRon]

In some cases, overfilling can result in some moving engine parts being somewhat submerged in oil when they shouldn't be. While these moving parts are submerged, they can create an oil/air foam that can cause issues with the oil pump. Bad things can happen when the oil pump has an issue suppling oil to the engine, very bad.

True of a wet sump system, but not going to happen with a dry sump system. The problem with the Spyder, especially the 998 motor, is that the crank case vent system is poorly designed. Even filled properly, you will get too much oil vapor into the airbox. If overfilled, you can get a good amount of liquid oil into the airbox. We've seen air filters completely soaked with engine oil.

The oil vapors gum up the throttle bodies and, especially on the Fly-By-Wire models (2010-2013 RT), that will give you a good deal of grief. There are cheap and simple ways to prevent this problem detailed in posts here on Spyderlovers. If I get time I'll come back and link to those.

The 2nd thing that can happen is you'll start to get gasket leaks. They can happen anywhere. But valve cover gaskets seem to be the weak point. Not a cheap or easy fix.

As for how much is too much. I don't really know. But I highly recommend staying with the mark on the dipstick. Why experiment to see at what point bad things start to happen?

 

[Peter Aawen]

True of a wet sump system, but not going to happen with a dry sump system. The problem with the Spyder, especially the 998 motor, is that the crank case vent system is poorly designed. Even filled properly, you will get too much oil vapor into the airbox. If overfilled, you can get a good amount of liquid oil into the airbox. We've seen air filters completely soaked with engine oil.

... <snip> ...

While ^ that bit is normally true, it's not always the case and there are worse things that can (and DO) happen!

For instance, if a Spyder, with a full & correct oil fill, then spends some time sitting and not running, and now the operator wants to go for a ride, but without following the correct 'get it up to temp' procedure, checks the oil (engine off & all cold) only to find the dipstick shows little or nothing on the stick at all, because the oil that was in the reservoir has drained back into the engine & its pick-up points... So the owner adds more oil until the dipstick shows the level is right up to the Full mark. That might initially end up as a messy engine, but do it again, and it's not likely to end up resulting in anything as minor as a really messy Spyder engine, or even just blown gaskets &/or seals!

Yes, this is more of a problem with the V-Twins, but it does still happen on some 1330's! If the quantity of oil added isn't too much, the scenario Ron describes above is the usual result. But that's not all that happens if the quantity is more than 'just a little', or when the next time the owner checks the oil level, they still do it when everything's cold so that at least some of the oil has drained from the reservoir and is filling the galleries & pooling in the pick-up points, and then they fill the reservoir to the Full level AGAIN!! And don't even THINK that can't happen even once, cos it does happen, sometimes a few times before suddenly, things start going pear shaped rapidly!! It happens Waaayy more often than you credit!

As to 'how much is too much extra oil', there's no really definite answer to that. Most bikes will get away with 'a little', but some don't even seem to tolerate that, doing everything Ron's described above very quickly the oil goes much above the Full level on the dipstick when checked using the correct procedure (especially those Spyders with 998 motors!) Some bikes will seemingly get away with more excess oil than that, maybe even seemingly surviving a 1/2 a quart or more. But really, anything much more than that correct level is likely to mean that there's rotating components inside the engine that are at least splashing around in oil when they shouldn't be! And you also need to worry about where and how much of the oil that starts out pooling in the air filter goes once it becomes enough to actually start draining anywhere - if you're lucky, it might all drain out and simply make a mess outside the engine, or maybe it'll blow a gasket and leak out that way; but if there's any oil in the air filter, some of that is going to end up in the air intake. A little oil in there might get sucked into the engine and be burned off fairly readily with no ill effect, but how much will it take before it's too much to burn properly?? And don't forget that the more oil you get in the air filter, the more oil will likely end up in the intake tract, even if only initially as a fairly wet 'vapour', so that eventually, at the very least end up with a messy and clogged intake tract, killing performance, fuel economy, and choking the engine of oxygen; but eventually, if left unresolved, you will end up with some liquid oil in the cylinders... We all know that oil doesn't instantly ignite and burn off readily at engine starting temperatures, but do you think anything more than saaay, a teaspoonful of liquid oil will compress much?! If not, what's going to happen to that, it's gotta get out somehow, or at least the now solid slug of oil under pressure does, and if it's enough, it'll need to do that before it burns &/or the exhaust valve opens, too! You can be assured it'll take the easiest way out, usually thru a piston top or a valve seat!

Then there's all the other stuff that could be going on at the bottom end to consider too!! Now you'd think that because wet-sump engines basically always mean there's going to some oil splashing around the crank shaft & con rods, that shouldn't be a problem at all... but the reason some engines run dry sumps is because the designers wanted to minimise engine height (no need for a deep oil pan below the crank); minimise oil surge issues, windage, or the pick-up sucking air due to oil slop & surge when cornering or manoeuvring, especially if doing that fast/hard/aggressively, so no biggie here); they also very likely wanted to avoid any performance sapping 'slapping and splashing around in a pool of oil' in the components that they want to spin fast and smoothly, cos all that 'splashing & slapping' stuff adds drag and imposes repeated impact onto those important parts, parts that, since they weren't designed/intended to handle slapping into a pool of oil all the time, the designers could make lighter to help the engine spin even faster (could be a biggie here); and then there's also the fact that pumping oil directly from a reservoir into the places needing oil is a much better way of ensuring that oil arrives at the appropriate pressure and flow rates for the components that really need it; and probably a few more things besides. All good stuff, IF that's what ends up happening and no-one over fills the engine with oil!

But when you add too much oil to a dry sump engine (and asking 'how much is too much' is basically the same as asking 'how long is a ball if string'), you start bringing at least one if not a few of those things that were supposedly 'designed out' back into play; and even before you add much more in the way of 'too much' oil that can be catered for simply by blowing it out thru breather vents or bursting seals, you've probably started reducing your engine's performance capability simply by having more power sapping splashing and component slapping going on; and the more 'too much oil' there is, the more you're likely to be damaging important internal components that had been designed lighter because they were going into a dry sump engine and so weren't expected to need to beat the crap out of a puddle of oil on every rotation, or run in a cloying pool of oil and kill your performance amongst other things!!

Did I ask you about how much oil compresses already?? Cos it DOESN'T compress much at all!! So you really don't want too much more oil in than (maybe) 'just a little' too much in there, and even that much is really questionable!! A messy engine & blown seals or gaskets is the BEST you can hope for!

 

[djh3]

As mentioned, gaskets start to leak, and oil for some reason even on wet sump bikes ends up in the air intake. As the crank splashes the oil it vaporizes and the PCV (crankcase vent system) recycles gases back thru the air intake.

 

[Cobranut]

Once I established the correct amount of oil in mine via the overly complicated factory procedure, I figured out my own quick level check.
I start the bike before a ride, let it idle while I remove the access panel, and check it with the engine idling.
It works out to be just above the lower level mark on the stick. If it ever got below that, I'd add a bit, but it's never seemed to use any oil so far.

I have a dry sump on my race car, and it's checked with the engine hot and idling, as that's the only sure way to know there's no excess oil in the crankcase. The level isn't as critical on a dry sump anyway.

 

[Little Blue]

My Tip: Check your Spyder oil level the 'Correct Way' and then enjoy.

Life is to short for me.
Ryde Healthy and Stay ahead of your game.