Oil on max level

[HertsBiker]

...doesn't seem any good on any of my revvier machinery. They all run better mid point or on minimum. Any reason manufacturers would recomend what is virtually an over full crank case? anyone else run mid point in preference? any harm to running on minimum?

[Crusoe]

on the max when hot or cold? Lots of performance cars need the oil to be measured warm and then they go below the max when they cold down, being at max when cold could be over filling.

[Codswallop]

A lex said:

Mine is currently leaking as the previous owner did indeed fill it to the max!

Annoying.

Is it leaking to the max?

'Cos it's a self service feature otherwise. My car self services roughly every 6,000 miles.

[Tango13]

Depends on the engine, Hondas RC30 actually needed to run 1/4" over the full mark to stop it destroying its big ends.

[littleredrooster]

A lex said:

If its filled to the top the engine has a propensity to blow the crank seals...

I've heard this so many times over the years; I'd love someone to provide a plausible explanation of how this can possibly happen. Oil seals provide a seal against pressurised oil. That's what they are designed for, that's what they do. It matters not whether they run submersed or not, I still fail to understand how an internal oil level can induce failure.

[Dimski]

Tango13 said:

Depends on the engine, Hondas RC30 actually needed to run 1/4" over the full mark to stop it destroying its big ends.

I overfill my Locoblade with oil to help oil surge. A bike leans into corners, a car doesn't. To the full mark, + 250ml IIRC.

- ETA This is specific to my situation, it's not standard practice. OP, I'd assume you're best off with an answer from someone who knows about your car in particular!

Edited by Dimski on Tuesday 6th December 13:34

[FreeLitres]

Only just fill to the minimum. Saves weight.

[HertsBiker]

littleredrooster said:

I've heard this so many times over the years; I'd love someone to provide a plausible explanation of how this can possibly happen. Oil seals provide a seal against pressurised oil. That's what they are designed for, that's what they do. It matters not whether they run submersed or not, I still fail to understand how an internal oil level can induce failure.

my 400cc single blows oil out the breather when thrashed, but only when the oil is above half way! stupid design.

[DB89]

I know the vtec system in my Civic Type R rely upon oil pressure to work correctly, so I'm keeping it one the max.

[NateWM]

Ditto. My Accord also relys on oil pressure for the VTEC engagement, so that's one reason. Another is because if you let the level get below half way, the camshafts aren't lubricated properly and can "wear" out quicker.

[k15tox]

Can't imagen the engine blowing any seals unless you've put about 2 litres to much in.

Too much oil pressure will get vented by your crankcase breather and put into the inlet

[Jimbo.]

Another is because if you let the level get below half way, the camshafts aren't lubricated properly and can "wear" out quicker.

Surely as long as the oil pickup is covered, you're fine?

[Kenny-Mack]

i found my old 200SX didn't like running near min, basically on min i would see pressure fluxuactions on the oil pressure guage, so my theory is minimum was actually below minimum because that really shouldn't happen!

[littleredrooster]

k15tox said:

Can't imagen the engine blowing any seals unless you've put about 2 litres to much in.

Too much oil pressure will get vented by your crankcase breather and put into the inlet

Vastly overfilling to the point where the crank is frothing the oil could cause massive crankcase pressurisation; this would be vented out of the breather not the seals, but it is not oil pressure which causes this.

[Classic Grad 98]

Jimbo. said:

Surely as long as the oil pickup is covered, you're fine?

Yep- until you go round a corner and the oil sloshes to one side of the sump, and the pickup draws air.

The loss of performance is caused by crank windage. If I fill my engine to 'MAX', I lose at least a second a lap!

As others have said, 'Max' level is a safety margin for those who never check their oil level.

[stek]

Oil pressure is oil pressure, so long as the pick up is in oil then I can't see how being at max will blow oil seals (Merc)