Oil Overfilled by 1/8 in is that a problem

the toyota book says 3.9. most oil change guys and/or techs are deathly afraid to deviate from toyota's recommended numbers for employment retention reasons (aka, not getting fired!!). this results in a slight overfill. don't blame them for following the book.

btw, those "express lube" places employ anyone under the sun to do oil changes. they pressure those guys to no end. time over quality. don't go to those places. in general techs are more experienced, more serious about their job (they've invested in lots of tools anyway) and know Wth they're doing over random oil change people.

no need to refer to these people as children, now. that's toeing the line. you go into DH's shop and talk to him like a child and he won't touch your car, ever. generally people don't like being told how to do their job.

got proof that it's bad for mpg? unless someone has documented proof, it's just another prius myth.

abnormally high head pressures/frothing won't show up unless it's a GROSS overfill. way, way over 4 quarts. 1/8 in over the line is nothing to worry about.

 

Galaxee, Might I might respectively disagree. I have had my oil over filled 3 times and each time I take a MPG hit. You get better MPG between 3.5 and 3.9. When the dip stick is between the half way point and the top it does better. It appears to make a difference. 4 quarts does not cut it. I hate to be derivative but that has been my limited experience. I am awaiting the 10k double blinded crossover study! We will all be able to rest easier then.

 

IN the back of my 06 manual for the prius.. it says 3.7... maybe they lowered it?

I little shoudn't hurt, I'm sure the engine is much tougher than that.. but I would expect that less pressure would be easier on the engine than more...
I looked around a bit... its hard to find much documentation on the subject... most of the bad is where someone made a gross error and put way too much... myself.. it seems common sense if it improves mpg, then its easier on the engine as it has less internal resistance.

If the prius veterans say a little less helps.. I have no reason to challenge it.

 

the 05 says 3.9- maybe they corrected it then. good.

okay.

let's try looking at the converse situation here. less lubrication is also harder on the engine than more. insufficient lubrication would cause increased friction and therefore lower mpg. and probably seize your engine if severely deficient.

it seems common sense if it improves mpg, then its easier on the engine as it has less internal resistance.
but here you're using reverse logic. i asked if you have proof that a slight overfill decreases mpg. you're working on the assumption that it does, and basing your logic upon that. do you see what i'm trying to point out? my point here is that i have seen no documented proof. where is the proof? i am a scientist. i do not believe until i see.

 

The real thing I see as credible evidence is the better mpg prob means the engine is happy!

 

oh all right. quit your smilin' at me, you're taking the wind out of my debate sails

:lol:

 

eh, last minute additional thought:

who knows if an ounce of oil is gonna really make the engine UNhappy? that's what i wanna know.

 

How could I have forgotten crossover. I will retire while I flagellate my self. There I am renewed... I will not make that mistake again. All two of the three times where during the summer and relatively stable temps and I lost 3-4 MPG over what I got after I pulled off the excess. Each time I was more like a quarter of an inch over or maybe 3/8. Clearly I had 4 quarts. In fact one time the person who did the fill said I had 4 quarts. After pulling off 1/2 quart or so (not exactly measured) but the dip stick was a bit more that half way over the half way mark. A very minimal study to be sure. Placebo effect? Not sure. Clearly a double blind crossover study is indicated. Shall we writ a RFP to the NIH. 2.6 M should be enough to do the study and well be comfortable for each of us while we do it. MD/ PhD candidate should push us over the top! Do you know any republicans my contacts are all democrats and for the present that will not cut it.

 

I see it as kinda like loosening your belt.... It just "feels" better.

 

heck, i can get an MD/PhD candidate, they're all over the place here.

scientist? republican? HA HA HA!!!!!

i personally think we should look at around 3.5 M...

 

I like 3.5 but I already have the MD and you are the Candidate that should put us a leg up. Now all we need is someone in the Bush Administration who does not hate us. How can we spin this?

 

Wow.. Hdragas... you tempt me..... I have a drill with a little pump "you can pick one up at the marine store.... maybe even auto store" and the drill acts to spin the pump. One hose goes down into the dipstick tube and the other into a cantainer....

I intend to fill 1/4 inch below the full mark with my next oil change, but I may just pull some off beforehand to see what happens?....

In your most humble opinion... :lol: what would you expect to see from 1/8 too much to 1/4 below the fill mark as far as mpg improvement?.... any guesses?

 

Your tire pressure seems excessively high. 44 is the max cold pressure for OEM tires. Although you might add a mile or two per gallon, you run the risk of damaging your tires or losing traction because the treads won't be able to grip the road. Tom and Ray Magliozzi suggest no more than 3-4 lbs over recommended, max.

 

DH's hypothesis is that the mpg drop is due to this:

excess oil will return through te PCV system into the intake, and what gets into through the air intake will be burned with the gas, which isn't so hot for mpg, and what doesn't get carried with the air into the cylinders gets pooled in the bottom of the air intake. modern air intake manifolds are designed to direct airflow in a certain manner. the oil in the intake changes the airflow pattern, changing how well the gas is dispersed.

as far as oil overfill relates to pressure inside the engine, it's known that increased pressure inside the crankcase wouldn't affect mpg. extra oil inside the engine cannot physically restrict engine operation. it would, however, affect the oil leak situation. (blown out seals from too much pressure and in extreme situations, oil blowing past valve seals)

 

I wonder what is the actual mechanism that allows for better mpg with less oil then?

 

no oil in the air intake.

 

Sorry, I missed it the first time.... I can see how that makes sense...

 

That is plausible.

I think we covered this before, but how about *rate* of fill? That is, if the shop has a bulk lube dispensing system and the reel for the hose doesn't have a restrictor orifice in it? The orifice looks like the jet in an oil-fired furnace, and is used to limit the fill rate from the 3-5 gpm put out by the bulk oil pump.

Although it's somewhat hard to see, the PCV system in the Prius *might* be sensitive to a rate of fill that floods the top of the cylinder head. On something like my old 1984 Ford F-150, the PCV is on the passenger side valve cover, and the oil fill is on the driver side.

I can pour in 6 litres as fast as I want and have never had any problems with my 302. With an inline motor, the PCV will be more exposed.

As far as my Prius, whether I put in the book amount or 3 litres even, I haven't noticed any difference in fuel economy.

 

My car has the oil right at the full mark. What options can one use to pull out 1/2 qt. of oil? I have visions of trying to ease a thin stream of oil out and the plug dropping out. If it's a hassle, I was thinking of changing the oil at 1000 mi. to get rid of the break-in oil. But if it's easy, improving gas mileage would be nice. We're at 38.2 now.

 

As far as drawing out small amounts of oil, there are little hand pumps you can buy at auto parts places that can pull the oil out through the dipstick.

I have an oil sample kit that I use to sample the used oil from my Prius, and I draw it out through the dipstick tube. Companies like Mityvac even make oil change gadgets that will draw the oil out the dipstick tube:

http://www.mityvac.com/info_sheets/07300.pdf

Why do you want to change the oil at 1,000 miles? Completely unnecessary and a waste of time/money. You can search the forum for topics I've posted on used oil analysis, this motor is very easy on oil.

Matter of fact, the EU market Prius running the "proper" ACEA spec motor oil has a 12 month or 16,000km oil change interval, with no ill effect.