Optimum oil level=less resistance

[C3H8]

most car company's say NOT to add oil unless it is BELOW the add line, just as Frank Lee said.

The reason for this, however, is not always clear. i know from personal expierence that most automobile oil pans can phgysically hold more oil then recomended without the oil level touching the crankshaft. Add to that, that when the motor is actually running, oil is being pumped through the engine and draining back, so the oil level in the pan will be less.
So why would they say not to add oil if not below the add line? It could be as frank lee said, wind age and the like. however being that the oil level in most engines is not even close to the crank, i would hazard a guess that they simply want to reduce the total amount of oil consumed. (if you add a quart a few days before getting an oil change, for example, the added quart is probably wasted). I think they say this so they can claim to the epa their cars use less oil. I don't think it has any part in fuel economy. All automobile engines use positive displacement oil pumps. As long as the pick up tube is submerged in oil, and the crank isn't whipping it up from grossly over filling, then you are good to go. It is only on splash lubricated engines, that oil level dramatically effects horsepower and fuel economy. for example, 5hp briggs and stratton racing go carts. People who run these things typically run them with as little as 16 to 12 ounces of oil. These engines get lubrication from a dipper on the bottom of the con rod which flings oil everywhere. This is called splash lube.

keep in mind this is only my guess. i always keep my oil topped up. if i am going on highway trip i will even overfill by a quart or so.

[Frank Lee]

I know on small block Chevys the oil is VERY close to the windage point.

[Arragonis]

Originally Posted by C3H8

So why would they say not to add oil if not below the add line?

I think it is now because of cats. If you overfill the excess oil is blown out via the relief valve and vents via the exhaust where it gets into the cat and basically knackers it. My TDI Fabia has stickers all over the place warning about this as did my petrol FIAT Bravo and Ford Mondeo.

I hate cats. And I hate catalytic converters.

[Jyden]

Originally Posted by Frank Lee

Jyden: you have no, and cannot obtain, any proof of that.

Yes I do

Not only does the oil circulkate more, it will also be at a higher temp, which will tend to break it down more quickly.

I've been running BMW motoercycles for many years, and fitting a bigger oilsump which hold more oil, does three things. One - it mean I can go longer before oilchanges, and two I can run whith more stable oil temps in the engine. Thirdly theres less wear on the engine due to improved lubrication and cooling.

It's a well known fact for these engines, and I dont see why it should be any different for cars.

If you have less oil to do the same job, you will wear it out quicker. Everytimes it circulates it wears a little, and less oil also means e somewhat reduced cooling effect, as the oil stays a shorter time in the sump and has less time to cool down.

This is also why some vicihles are equipped with an oilcooler.

[Arragonis]

Is the BMW cycle air coolled ?

[C3H8]

almost all bmw are aircooled. The K series are watercooled. but most are air. My r1100s boxer cup race bike has no watercooling. what it does have, is a massive oil cooler in the front fairing right under the headlight.

my pops r1100R has dual oil coolers on top of each opposed cylinder.

on both bikes, there is a clear glass lens so you can actually SEE the level of the oil. and when the oil level is low, the bikes run noticeably warmer according to the temp gauges.

Boxer Cup:


R1100R:

[Rockstock]

Thanks for the insight. I never thought I would dare let the oil get down to the fill line, but that makes sense that the engine will still get proper lubrication at that level. As far as over heating, I've never seen the temp gauge move at all once it is up to normal operating temperature, so on this application less oil won't affect the temp. It definitely makes sense that the oil will brake down faster, but in reality the current oils on the market will last way longer than 3,000 miles. I've even started to notice oil changing guild lines switching from 3,000 to 4,500 or 5,000 miles from auto makers and aftermarket companies.

I'm really interested to see what the increase in mileage will be. I expect on my normal route average trip mpg will go from about 42 to 48 bases on initial results. I'll post my findings in a couple of weeks after I have a bunch of observed drives to compare.

[Frank Lee]

Originally Posted by Jyden

Yes I do

Not only does the oil circulkate more, it will also be at a higher temp, which will tend to break it down more quickly.

I've been running BMW motoercycles for many years, and fitting a bigger oilsump which hold more oil, does three things. One - it mean I can go longer before oilchanges, and two I can run whith more stable oil temps in the engine. Thirdly theres less wear on the engine due to improved lubrication and cooling.

It's a well known fact for these engines, and I dont see why it should be any different for cars.

If you have less oil to do the same job, you will wear it out quicker. Everytimes it circulates it wears a little, and less oil also means e somewhat reduced cooling effect, as the oil stays a shorter time in the sump and has less time to cool down.

This is also why some vicihles are equipped with an oilcooler.

Driving with less oil in the engine wears out the oil quicker, so this willf orce you in to change oil more frequent.

OK you have brought up a situation where your point is likely correct.

Still, 99.9% of us with automotive lumps- esp. American ones- do not have engines stressed highly enough for this to be a factor. ESPECIALLY if one is driving in eco mode.

[Frank Lee]

Originally Posted by Rockstock

It definitely makes sense that the oil will brake down faster, but in reality the current oils on the market will last way longer than 3,000 miles. I've even started to notice oil changing guild lines switching from 3,000 to 4,500 or 5,000 miles from auto makers and aftermarket companies.

No road vehicles with oiled brakes that I'm aware of.

I jest.

But "starting" to notice change intervals >3000m?!? COME ON! It's been longer than that for decades! It's not the oils as much as it is the widespread use of EFI, which does a better job of not dumping huge amounts of gasoline into the sump.

[Rockstock]

Uh, yeah I meant break not brake

But still I agree that the oil will not break down before a normal oil change