How much oil is too much oil?
How much oil is too much oil?
Author
Discussion

omniflow

Original Poster:

3,592 posts

174 months

Wednesday 27th November 2019
quotequote all
I've overfilled the oil in my car. It's a 3.2V6 Alfa engine. The oil is higher than the high mark on the dipstick by about 1/3 of the distance between the high and low marks on the dipstick.

Do I need to siphon some out, or will it be ok to drive?

Pericoloso

44,044 posts

186 months

Wednesday 27th November 2019
quotequote all
It's surprising how little oil added to an engine can make a big difference to a dipstick.

I reckon you're okay.

Probably 0.5 litre too much.

Tony1963

5,808 posts

185 months

Friday 29th November 2019
quotequote all
I’d be syphoning some out. I wouldn’t be able to enjoy the engine with that overfilled oil on my mind.

Many years ago I collected a rental car that had been overfilled. Blew the head gasket while cruising on a motorway at 70 ish.

Why risk it?

HJG

580 posts

130 months

Friday 29th November 2019
quotequote all
Drain it back out until the correct level.
You'll be churning it up in the sump, creating unwanted aeration. Worst case in a big overfill is a hydrolocked engine (crank pulls piston down but so much oil beneath the piston that it can't move and crank pulls rod and gudgeon pin straight out of the piston).

xjay1337

15,966 posts

141 months

Friday 29th November 2019
quotequote all
Tony1963 said:
I’d be syphoning some out. I wouldn’t be able to enjoy the engine with that overfilled oil on my mind.

Many years ago I collected a rental car that had been overfilled. Blew the head gasket while cruising on a motorway at 70 ish.

Why risk it?
Really?

Maybe if it's brimming out the top of the engine.
Or perhaps head gasket is a completely unrelated fault.
Very unlikely over filling engine with oil

I run 1L over fill on my car without issues and have done for 20k miles.

0.5L or so is NOTHING do not worry about it.


GreenV8S

30,999 posts

307 months

Friday 29th November 2019
quotequote all
That sounds like a relatively small amount of excess oil and I wouldn't expect it to cause any problem.

The main risks are that the oil level at rest reveals a leaking gasket (you'll notice that soon enough) or that the oil covers the windage plate and starts getting beaten up by the crank - in that case you'll get rising oil temperatures, falling pressures, power loss and excessive oil blow-by. If you don't get any of those symptoms, you're fine.

I don't have the same car, but when I go on track I routinely overfill by half an inch to reduce oil surge and have never encountered any problems from that - I think the max fill level always has a considerable margin of safety in it.

Tony1963

5,808 posts

185 months

Friday 29th November 2019
quotequote all
xjay1337 said:
Really?

Maybe if it's brimming out the top of the engine.
Or perhaps head gasket is a completely unrelated fault.
Very unlikely over filling engine with oil

I run 1L over fill on my car without issues and have done for 20k miles.

0.5L or so is NOTHING do not worry about it.
I’ve no idea about the details. I was given a replacement and was on my way.

One litre over? No way. No point, unless it’s drinking the stuff.

The OP’s engine isn’t one I’d go experimenting with. If it was an old hulk of a knackered donk, maybe. But jeepers, I’m not recommending an engine rebuild, just the removal of half a litre!

xjay1337

15,966 posts

141 months

Saturday 30th November 2019
quotequote all
Tony1963 said:
I’ve no idea about the details. I was given a replacement and was on my way.

One litre over? No way. No point, unless it’s drinking the stuff.

The OP’s engine isn’t one I’d go experimenting with. If it was an old hulk of a knackered donk, maybe. But jeepers, I’m not recommending an engine rebuild, just the removal of half a litre!
Yes. 1L over.
Due to trackdays and concerns with these engines about oil starvation.
It's also got a larger oil cooler.

Many of the hardcore Nurburgring users do this as well as race teams.
0.5L over is nothing to worry about and I wouldn't even bother draining it out.

If you don't know about the details then don't use it as an example. It spreasds mis information.

Oil level isn't really related to head gasket failure in any way. Do you think oil pressure could ever be higher than the pressure within the cylinder itself?
Unless the oil level was high enough to go up to the piston rings . But that would be 3 to 4 L over on a 6L capacity engine.

So OP has nothing to worry about. However, if it would play on his mind which is fair enough , then drain the extra.
But he doesn't need to!

HustleRussell

26,128 posts

183 months

Saturday 30th November 2019
quotequote all
In my view, an overfill of 0.5-1l is probably not going to cause any kind of issue to the engine itself. However the engine does breathe it’s own crankcase vapour and an overfill will cause more oil to get into the inlet. This just makes a mess really. I’d reduce the level simply because it is overfilled and it’s easy to reduce it.

Tony1963

5,808 posts

185 months

Sunday 1st December 2019
quotequote all
xjay1337 said:
Yes. 1L over.
Due to trackdays and concerns with these engines about oil starvation.
It's also got a larger oil cooler.

Many of the hardcore Nurburgring users do this as well as race teams.
0.5L over is nothing to worry about and I wouldn't even bother draining it out.

If you don't know about the details then don't use it as an example. It spreasds mis information.

Oil level isn't really related to head gasket failure in any way. Do you think oil pressure could ever be higher than the pressure within the cylinder itself?
Unless the oil level was high enough to go up to the piston rings . But that would be 3 to 4 L over on a 6L capacity engine.

So OP has nothing to worry about. However, if it would play on his mind which is fair enough , then drain the extra.
But he doesn't need to!
That all makes sense, especially for your track car with high g cornering etc. And maybe you wouldn’t worry, maybe most people wouldn’t. But... I would smile. Knowing my luck there’d be a weak point somewhere and it’d all go wrong.