keeping oil at full vs between high and low marks?

[friendly_jacek]

I always kept oil at full mark. However, Prius forums report decreased MPG with oil at full and especially above full. This makes sense since more oil = more drag and lower oil temp and higher viscosity.
I consider using lower oil levels in winter for short trips to help keep oil temp higher. There is no issue with oil consumption in my car whatsoever.
Any drawbacks from lower oil levels?

Please empiric evidence only and no bashing.

 

[StevieC]

As long as you are in between the low & max/full level your engine will be fine.

Be very careful if you intend to lower it and do regular checks to ensure it doesn't fall below the safe "low" line.

Also keep in mind that having less oil in your engine will shorten the OCI because there is less additive.

 

[CharlieJ]

I like big sumps. I put 5 quarts in my 3.

 

[Nayov]

Hypermilers run their cars a quart below the "add" mark. I don't know how much they gain but that's insane. I just round off the quarts that makes the level between add/full (eg, Sentra cap is 3.2 but I always just put in 3 quarts; level never goes down within the 5K OCI).

 

[demarpaint]

A qt below the add mark? That would be down 2 qts in my car? Is the risk/reward going an extra 5 miles on a tank of gas worth it? An engine can run all day long w/o issue being low 1 qt of oil, but why risk it? Down 2 qts in a small sump engine is insane.

I fill mine to the full mark, and get 5 miles less/tankful of gas.

 

[Nayov]

Originally Posted By: demarpaint
A qt below the add mark? That would be down 2 qts in my car?


Technically, you'd only be down a quart (still unsafe, long term).

Now, keep in mind that hypermilers are about "bragging rights"
so they will go to extremes.

 

[BuickGN]

Originally Posted By: Nayov
Hypermilers run their cars a quart below the "add" mark. I don't know how much they gain but that's insane. I just round off the quarts that makes the level between add/full (eg, Sentra cap is 3.2 but I always just put in 3 quarts; level never goes down within the 5K OCI).


That's called not seeing the big picure. More frequent oil changes or the possibility of engine damage far outweigh the poteneial .000001mpg increase.

 

[dwendt44]

Some engines seem to like being a half quart low or similar level other than FULL.
I've had one like that.
If I left it a half quart low, it would stay there, add to the full line, it would burn/use that half quart and stay at the lower level.

 

[BuickGN]

Originally Posted By: friendly_jacek
I always kept oil at full mark. However, Prius forums report decreased MPG with oil at full and especially above full. This makes sense since more oil = more drag and lower oil temp and higher viscosity.
I consider using lower oil levels in winter for short trips to help keep oil temp higher. There is no issue with oil consumption in my car whatsoever.
Any drawbacks from lower oil levels?

Please empiric evidence only and no bashing.


My thought is that as long as the oil is not coming into contact with the crank counterweights, there will be no difference between full and low.

The only argument you could make is that less oil will heat up and thin out quicker.

Being the oil nerd that I am, I've checked the engines I've rebuilt with water in the oil pan with the recommended amount or sticking the dipstick into the block to see exactly where the level would come to. Most that I've seen would take 3+ quarts over to actually come into contact with the crank.

 

[Kestas]

Oil also cools the engine. Again, the risks outweigh the benefits. They'd be better off losing a few pounds off the driver.

 

[Geonerd]

Originally Posted By: BuickGN


My thought is that as long as the oil is not coming into contact with the crank counterweights, there will be no difference between full and low.

The only argument you could make is that less oil will heat up and thin out quicker.

...most that I've seen would take 3+ quarts over to actually come into contact with the crank.


That sounds about right.

Hypermiler OCD puts BITOG member's symptoms to shame. They will do darn near anything to squeeze out another 0.1 MPG, and don't seem to mind trashing the car in the process. Visit the forums at http://www.cleanmpg.com/ and be ready to cringe...

 

[Mark_S]

My car is listed as having 5 quarts capacity. When I change the oil and filter, it comes up to the full mark on the dipstick. After about 3,000 to 4,000 miles, it's down a little less than 1/2 quart, so I top it off until the next oil change. I try to keep it simple.

 

[BuickGN]

Originally Posted By: Geonerd
Originally Posted By: BuickGN


My thought is that as long as the oil is not coming into contact with the crank counterweights, there will be no difference between full and low.

The only argument you could make is that less oil will heat up and thin out quicker.

...most that I've seen would take 3+ quarts over to actually come into contact with the crank.


That sounds about right.

Hypermiler OCD puts BITOG member's symptoms to shame. They will do darn near anything to squeeze out another 0.1 MPG, and don't seem to mind trashing the car in the process. Visit the forums at http://www.cleanmpg.com/ and be ready to cringe...


I'm not ready to go over there yet. It may cause me to go to a very dark place lol.

 

[ekpolk]

Originally Posted By: Nayov
Hypermilers run their cars a quart below the "add" mark. I don't know how much they gain but that's insane. I just round off the quarts that makes the level between add/full (eg, Sentra cap is 3.2 but I always just put in 3 quarts; level never goes down within the 5K OCI).


I think you're painting with a pretty broad brush. "Hypermiling" is not one "thing" in and of itself, it's a group of techniques, some quite reasonable, some, as you suggest, pretty out there. I've become pretty good at what might be called "reasonable, situational hypermiling." No, I'm never going to run my engine critically low on oil (theory might be that lower oil vol will increase oil temp, thinning the oil, nutty, but true), I don't lose sight of the fact that my time is more valuable than saving a cup or two of fuel driving to work, and most importantly, safety and consideration for others take precedence over hypermiling (e.g. no pulse and glide if it messes with other traffic, etc.).

 

[GMorg]

I routinely run 3.5 quarts in a 4.5 quart sump.
3.5L V6, 2005 Montana SV6.

Older thread when discussed before:

http://www.bobistheoilguy.com/forums/ubb...true#Post671543

 

[BuickGN]

Originally Posted By: GMorg
I routinely run 3.5 quarts in a 4.5 quart sump.
3.5L V6, 2005 Montana SV6.

Older thread when discussed before:

http://www.bobistheoilguy.com/forums/ubb...true#Post671543


I read that post and I was about to say how crazy it was but I see you change more often to sort of make up the difference.

You have a drag racing background and I saw how you said you mark the pans. I've done the same thing to see at what point the counterweights are going to whip up the oil.

In my experience, it takes a signifigant overfill to make this happen.

My question to you is what are you gaining assuming the crank never comes into contact with the oil at the factory fill level?

 

[element_42]

Originally Posted By: dwendt44
Some engines seem to like being a half quart low or similar level other than FULL.


That's just poor engineering or dipstick calibration.

 

[element_42]

Originally Posted By: BuickGN
Originally Posted By: GMorg
I routinely run 3.5 quarts in a 4.5 quart sump.
3.5L V6, 2005 Montana SV6.

Older thread when discussed before:

http://www.bobistheoilguy.com/forums/ubb...true#Post671543


I read that post and I was about to say how crazy it was but I see you change more often to sort of make up the difference.

You have a drag racing background and I saw how you said you mark the pans. I've done the same thing to see at what point the counterweights are going to whip up the oil.

In my experience, it takes a signifigant overfill to make this happen.

My question to you is what are you gaining assuming the crank never comes into contact with the oil at the factory fill level?


Good question. Imagine how low the sump must be when the oil's actually being pumped and is elsewhere in the engine, one hard turn and you're sucking in air which can cause all kinds of problems from the pump and air in the galleries to having momentarily dry bearings

 

[Captain_Klink]

Once the engine is running, the oil is in circulation, meaning a lot of oil is in the top of the engine doing its job. That's why I always keep it full right to the top, maybe 1-2mm over the top.

 

[y2k345]

Originally Posted By: Captain_Klink
Once the engine is running, the oil is in circulation, meaning a lot of oil is in the top of the engine doing its job. That's why I always keep it full right to the top, maybe 1-2mm over the top.

5mm here