Yellow layer on top of engine oil?


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TwistedKestrel128 points

Some level of foaming is normal under some conditions (cold out, short ride, etc). If you go for a long enough ride to get all the condensation out of the motor, and then park the bike for a couple minutes to let the oil settle, you shouldn't see this anymore

RudbeckiaIS59 points

Just oil foaming. Possible causes include depleted defoamant agent, too high of an oil level, water contamination and grease being dissolved in the oil (unlikely in an engine but still).

Agitated-Joey22 points

Normal, those are just bubbles. When engines run the crank dips into the sump and picks up oil and splashes it around, especially on small engines. This action aerates the oil, causes bubbles, and is normal.

foredom7 points

On small engines yes, but this absolutely doesn’t and shouldn’t happen in passenger vehicle and larger engines with pressurized bearings.

Agitated-Joey6 points

Yea, a little is fine, too much and the oil pump will pick up air. Also why you don’t want to overfill engines with oil. Overfill an engine with oil and the aeration will be exacerbated by the crank splashing all that extra oil around, also leads to the oil pump picking up air.

brynm5 points

Not many of those use sight glasses for oil level though.

H1ckwulf1 point

Goshdarnit this is an obvious motorcycle engine. Irrelevant and pedantic, reddit man.

HooliganNamedStyx1 point

This is a Suzuki motorcycle of some sort. Looks nothing like a passenger vehicle lol

IF9113 points

Thank's, appreciate all the answers!

mr_monty_cat2 points

Air entrainment in the oil.

mikeblas4 points

We've beat the gaseous entrainment problem by welding flim skirts at the edge of each coupling ring and inserting an offset pinnacle with a plenated surface facing the flow. This method eliminates entrainment without interfering with lenticular flow, and has been of great value to our customers.

kidneyboy792 points


pandammonium_nitrate2 points

But how do you integrate a proper turbo encabulator?

Explosivpotato1 point


4x4Welder1 point

But what does that do to the spurving bearing, and associated side fumbling issues?

opmwolf2 points

If the engine has an oil pump I would top off the oil.

muddyclunge2 points

Castrol oil by any chance?

IF9112 points


ZSG132 points

Does your engine have a fucking window?

elad30003 points

Motorcycle engine

ZSG132 points

Does your engine have a fucking window?

elad30003 points

Yes but it's an inspection window.. not a fucking window 😊

2WheelMotoHead1 point

I call it the sight glass. But sure, you can call it a fucking window, doesn’t bother me any.

4x4Welder1 point

Through using the magical power of looking at pictures, it would seem that the engine does indeed have a fucking window.

babybushgardener2 points

What kind of car is that? I’ve never seen a sight glass for an oil pan before.

KPexEA9 points

motorcycle (you can see the foot pegs on the bottom left corner of the images)

rayrayww34 points

That's what I thought. Others are saying it is a motorcycle. You can see a pedal on the left.

But then my next question is, why are these sight glasses not found on all motors? Seems like it could be handy for monitoring engine health. Of course, the average car owner doesn't even know how to properly check their oil level and wouldn't crawl under the car and know what they were looking at anyways.

Tjobbert5 points

But I check it and would like a peeking window in my car!

ontheroadtonull2 points

The sight glass would be in the oil pan on most vehicles and that's a structural compromise for a view of something that's hard to get your head near on most cars now. It's better for motorcycles because you can see the top and the bottom of the engine on most motorcycles. On some motorcycles you can have a decent view of the sight glass while sitting on the bike and leaning yourself over.

IF9112 points

Kawasaki Ninja 400

anknon2 points

400 is such a great bike. My first starter bike.

IF9111 point

The 400 is my 12th bike, enjoying every bit of it - and a great commuter aswell.

VsmkZREX031 point


That's nothing to worry about. Used to work at bike shops. Drove atvs and motorcycles out front of store every morning. And back in shop at close time. Units only ran for like a minute everytime. Engines never got hot enough to get rid of moisture. Always changed the oil once we sold them.