Not filling the oil to the top mark (on dipstick)

[uart]

How much do you think you'd have to overfill the oil in order to get excessive oil drawn up into the throttle body or intake manifold?

I own a 2005 Pruis and over at Priuschat forums I'm often getting into disagreements with people who only fill their oil to about half way (between empty and full marks) on the dipstick. They say that if the oil is too full it increases drag on the crank and can cause excess oil to get drawn into the intake.

I don't overfill but, but obviously I like to take it to the top mark on the dipstick. I'm pretty sure you'd have to significantly overfill (not just fill to the top mark) in order to get any bad effect like the above.

See for example this video : http://www.youtube.com/watch?v=7XvaDjKNHoI&feature=player_embedded

Notice how he's specifically saying not to fill it all the way. The fill spec is 4.1 quarts, which is probably a dry fill spec since 3.6 to 3.8 normally gets me about there on a drain and refill. A heck of a lot of people over at priuschat actually say to only use 3 quarts, which doesn't quite get you even half way on the dipstick. This seems like a totally daft idea to me, to deliberately leave yourself nearly a quart short on a refill.

What's peoples opinion on this.

 

[The Critic]

Technically, any point between min and max is acceptable and requires no attention.

Also, I have started seeing a few cars where adding the mfg specified capacity does not get the oil level to the max mark. For instance, on my friend's Fit, adding the specified 3.8 quarts will allow the oil level to reach 2/3 of the way between min and max. The quick lubes and dealers both fill that car with 3.8 qt, and do not bother to bring the level up to the max. When I confronted the dealer, I was given the line from the owner's manual-- that any level between min and max is acceptable and that they were not going to fill it to the max mark.

But to answer your question, I have noticed that some of the recent Toyota models will overfill if you add the amount listed in the manual. On the second-gen Prius, if you add 3.9 qt, I have found that this will bring the level past full. So, adding slightly less is actually a good idea in this case. As for an overfill impacting fuel economy, I have not tested this theory. However, remember that because a Prius is a high-mpg vehicle, even a small percentage loss in fuel economy translates to whole number losses in mpg, so people may be making a big deal out of something that is normally a moot point.

 

[uart]

Yeah the manufactures spec (4.1 quart dry, 3.9 quart refill) will get you overfull on the Prius. It's a common compliant that oil changes at the dealer almost always result in a fill to about 1/4" above the top mark on the stick. The used to happen to me all the time at the dealers, but now that I do my own changes I put it right on the top mark. Surely that should be a problem?

 

[rg200amp]

Anything between the max and min lines on the dip stick is fine.

What else is there to say??

I like to keep the level right under the MAX line.

 

[Bottom_Feeder]

Originally Posted By: uart
They say that if the oil is too full it increases drag on the crank and can cause excess oil to get drawn into the intake.

Hogwash. The oil level would have to be WAY over the full mark, like probably more than a quart or two for it to be high enough to be in constant contact with the bottom of the crank, frothing the oil and causing a minor amount of drag. I'm sure this rumor was started by some anal-retentive hyper-miling Prius owner at a fansite who knows just enough about cars to be dangerous.

The oily intake is an issue I can see being possible if the Prius engine has some sort of poorly-designed PCV system (entirely possible), but I'm also quite sure that it's more or less harmeless since a very small amount of oil is going to get into the cylinders past the rings and valve seals on every combustion cycle anyway. He's doing more harm pushing fuzzy shop towels down past the somewhat delicate throttle plate with metal tools! That small amount he cleaned up by doing so was a waste of time since you can only assume that there's more oil in the other areas of the intake manifold that you can't see by just opening the throttle plate.

 

[ARCOgraphite]

I had a yaris with the 1nzfe and it was a bit peppier with 1/2L low, but noisier. Car was driven HARD and this was only noticable with the engine in the upper rev range and hard cornering. The engine is happy with its required 3.5litre fill which brings it to max on the dip stick checked cold sitting overnight on a level parking spot. Check cold without a wipe and reinsert. OTOH, Subarus require a wipe and slow and careful reinsert.

 

[Indydriver]

Originally Posted By: Bottom_Feeder

]Hogwash. I'm sure this rumor was started by some anal-retentive hyper-miling Prius owner at a fansite who knows just enough about cars to be dangerous.

Agree 100%. The reason you should fill to the max line is so that you have some room for oil consumption while keeping your engine within normal operating parameters. As for the dealer who isn't refilling to the max operating volume, this is simply a cheap and potentially dangerous cost reduction (margin enhancement) technique that is cheating their customers and putting those who don't monitor oil level frequently (most) in danger of operating with below spec oil quantities before their next change. I'd find a new dealer.

 

[QuOk]

Filling my daughter's 2001 Prius results in the car throwing codes.It happened to me before i read about it:
""P3191 means the "engine did not start". P3190 means "poor engine power". Toyota recommends checking the basics first: air, fuel delivery & injection, spark & timing, compression. They also state incorrect oil level or even incorrect oil viscosity can cause these codes.""

When i lowered the level everything was fine.

 

[demarpaint]

Originally Posted By: Indydriver
Originally Posted By: Bottom_Feeder

]Hogwash. I'm sure this rumor was started by some anal-retentive hyper-miling Prius owner at a fansite who knows just enough about cars to be dangerous.

Agree 100%. The reason you should fill to the max line is so that you have some room for oil consumption while keeping your engine within normal operating parameters. As for the dealer who isn't refilling to the max operating volume, this is simply a cheap and potentially dangerous cost reduction (margin enhancement) technique that is cheating their customers and putting those who don't monitor oil level frequently (most) in danger of operating with below spec oil quantities before their next change. I'd find a new dealer.


I Agree! What confuses me is this. Lets say for the sake of argument an engine calls for 5 qts of oil with a OEM filter. Unless the engine casting is significantly thicker or thinner, or the oil pan is deeper, or the filter is larger or smaller by a significant amount, adding 5 qts is not going to harm the engine. It would be full. At that point I would start the engine, let it sit overnight and note where the oil level is on the stick, and that would be the full mark for my engine. You can even make your own full mark if its off.

Something else to consider, the fill tube could have been shoved in a little deeper or less, which would have an impact on the oil level. But if the mfg states to add 5 qts with an oil change and OEM filter, then 5 qts will do it. Changing brands of filters, no problem, just fill to the prior level and call it a day. JMO

 

[uart]

Originally Posted By: ARCOgraphite
The engine is happy with its required 3.5litre fill which brings it to max on the dip stick checked cold sitting overnight on a level parking spot.


Yes that sits pretty well with my experience too ARCO. 3.5L (equals 3.7 quarts) is just about spot on what it takes for me to get right on the top mark.

Quote:
Agree 100%. The reason you should fill to the max line is so that you have some room for oil consumption while keeping your engine within normal operating parameters.

Yeah that's exactly the point Indydriver. Any level between the low and high marks is "ok" in terms of the immediate health of the engine, but to knowingly under-fill 0.7 quarts at the very start of an OCI is silly. Who knows for certain when they're going to get some unexpected consumption or a slow leak or whatever, so in my mind underfilling 0.7 qts is like throwing away at least half of your safely margin.

 

[uart]

Originally Posted By: QuOk
Filling my daughter's 2001 Prius results in the car throwing codes.It happened to me before i read about it:
""P3191 means the "engine did not start". P3190 means "poor engine power". Toyota recommends checking the basics first: air, fuel delivery & injection, spark & timing, compression. They also state incorrect oil level or even incorrect oil viscosity can cause these codes.""

When i lowered the level everything was fine.

That's interesting QuOk. Can you tell us exactly how much it was overfilled and how much oil you needed to drain?

With the Gen2 Prius (2004-2009) the specified fill is 3.9 quarts but as pointed out above you generally only need 3.7 quarts to hit the full level on a typical drain and refill (with filter).

Most dealer service departments just fill the specified 3.7 quarts without checking the level. When I used to get my services done at the dealer it would be 1/4" over filled almost every time without fail. That small amount of overfill never caused a single problem for me, (though I still prefer to get it right on now that I do myself).

 

[TFB1]

Many high performance engines(I ain't talkin' Pruis here) have a windage tray between the upper region of the oil pan and the crankshaft... It's purpose is to prevent the turbulence of a high RPM crankshaft from whipping the oil in the pan, which can push oil into the upper areas of the engine... Plus the rods/crank whipping through a oil bath, robs a bit of horsepower(you economy folks think mpg loss)... The higher the oil level in the pan, the more likely turbulence will displace the oil, on a engine without the windage tray running a little low is a possible solution... I suspect most Prius owners just "think" they need to run the oil level a bit under full...

As far as fill, if the engine has a decent size oil pan, a quart low isn't going to cause a problem... Last OC on my '07 Grand Marquis in Nov '10, I put in five instead of the six it holds, been a quart low for the whole time and I haven't added(checked a couple days ago, still on add)... On that engine, even two quarts low wouldn't cause a problem...

 

[friendly_jacek]

Originally Posted By: rg200amp
Anything between the max and min lines on the dip stick is fine.

What else is there to say??


Not always. I posted about my interesting experiment with 1ZZ-FE engine back in 2009. Based on the same reading uart did on priuschat, I filled oil halfway between high and low to see it there is affect on MPG. There was none, but engine started oil consumption (at 65,000 miles or so) at that very same OCI and next oil change revealed 5-10x more metal powder on my magnetic oil drain as normally. I eliminated other possibilities
and kept oil full since. Oil consumption is present since, but metal on magnetic drain went back to normal again.

Only recently discovered, that Toyota admitted that the original dipstick had wrong markings and they should be 10 mm higher!

The half-way oil level turned out to be below low and caused damage to rings!

I bet many corollas are consuming oil for that very reason.

 

[Mr Nice]

I just round to the nearest 'whole' quart, no problems if my oil level is slightly past the max mark.

 

[QuOk]

UART:
I had it too the top mark on the dipstick,Maybe a hair over.
Took out 1/2 quart to get into the lower middle range of dipstick.

 

[RF Overlord]

I agree 100% with what uart and Indydriver said about oil reserve capacity. I'm not referring to the Prius specifically, but it seems to me that deliberately underfilling the crankcase and reducing your safety margin is silly. Even if you're the sort who regularly checks the oil so the chance of it dropping below the "add" mark is low, it just doesn't make sense to play with fire like that, especially with a motor that has a very small oil capacity to begin with.

Now if the manufacturer specifically authorises such a change due to manufacturing or design error, that's a different story.

 

[Eddie]

+1 Any level between the Add & Full line is acceptable. Since the crankshaft does not "dip" into the oil unless severely ever filled, that is a non issue. Lots of self-appointed experts will offer advice without ANY data or good references. Just go with the manufactures recommendation unless the manufacture has a TSB concerning oil level. JMO. Ed

 

[RF Overlord]

And another thing...I distinctly remember the owner's manual of a previous car stating that the manufacturer's quoted oil capacity was "approximate" and that the actual quantity should be determined by the dipstick. IOW, it didn't matter whether it took 5 quarts exactly or 5.5 or 4.9, when the oil was at the "full" mark, that was the correct amount.

 

[QuOk]

For the non believers:
Oil Level,Viscosity TSB

From my experience full mark on the dipstick is too much.
Many others have found this to be true.(2001-03)
Later models not as sensitive.

Any on these models just having a dirty throttle plate can even trigger the dreaded triangle of death lights.
Scared the [censored] out of me when it happened.Cleaned the TP and
all was fine.

 

[uart]

Originally Posted By: QuOk
For the non believers:
Oil Level,Viscosity TSB

From my experience full mark on the dipstick is too much.
Many others have found this to be true.(2001-03)
Later models not as sensitive.


Yeah I've seen that TSB. The prius detects the cranking speed and will throw that code if it cranks too slow. It doesn't directly detect the oil level or viscosity in any way. It simply means that IF the oil is way too thick (and the temperature very low) or IF it is really badly overfilled then the engine might crank to slow and cause the issue.

The reason why the Prius is cautious about sensing cranking speed and "tripping out" if it's not spinning freely is because it's basically got a monster 15 HP starter motor (mg1) that could inflict serious damage if it persisted trying to crank an engine that's somehow seized or otherwise unable to spin freely.

Notice that the TSB still recommends 3.9 Quarts as the correct fill volume. So I'd hardly say that it provides any supporting evidence at all for the premise that 3.0 quarts is preferable. That TSB certainly doesn't imply in any way shape or form that there could be a problem if the Prius filled with the correct grade of oil to the top mark on the dipstick.