Why it might be important to clean out the oil pan and pickup with a head gasket replacement,

I think @Mendel Leisk is suggesting to use the bottle with a "U" shaped tip to suck up residual oil left on the bottom of the oil pan below the drain hole.

 

I believe the drain plug points toward the center of the car.

If you raise the passenger front of the car, you'll get more oil out of the pan.
But, the few ounces of old oil is not a problem.

 

Thanks. Yes, that's what I finally figured out after multiple trials and errors with help of @Georgina Rudkus. If I finally get to do an oil change DIY on my own PP, I will try to remember to raise the front passenger side higher. But, the chances are I will not get to do the oil change myself on that car before I trade it in. Still have two free Toyota Care dealer oil changes and the car has only 4kmiles on it 6 months after purchase.

 

I don't see any asymmetry in the drain bolt loc, and really: if you're raising the front play it safe, use safety stands on the SAME notch on both sides is best.

 

Yes. Probably won't bother though, just musing.

 

Yeah, probably not much of a difference in total amount draining out. But I think the volume of the oil under the highest point of the drain hole flange would be slightly smaller if the drain pan is tilted such that the oil is now not covering the entire bottom of the pan. But it is not worth the risk as you say.

One additional thing is that, if I ever DIY the oil change on my PP, then the first time I will do it, I will be installing a Fumoto drain valve. That's what I did on our Pathfinder Hybrid. It makes the oil change so much easier and no fuss with a wrench or torque value and no oil spill or cleanup of messy oil drain container. Connect a short hose attachment, with just a twisting open the valve, the oil goes down directly into a 1.25 gal plastic jag I use for a waste container. I wanted to do the same for my son's Honda, but because I stripped the outer portion of the oil pan thread, I can no longer use a short-threaded valve. They don't make a longer thread one.

 

Hmmm ... That might explain why, when I drained the old oil using a suction pump the last time, instead of removing the plug, the dipstick showed a lower level than usual after refilling with the usual volume of fresh oil.

Relatedly, the relevant service manual page (which I saved a few years ago, thanks to Mendel posting it) shows "Dry Fill" oil capacity of 5.0 qt. (4.7L), compared to 4.4 qt. (4.2L) normal fill capacity with filter change. People tend to assume most of the difference is hung up elsewhere in the engine, but maybe most of it is trapped in the pan?

 

Hi folks, thx Georgina, for posting the picture. I took that pic so can vouch for it. In my testing, i discovered over 16 ounces of oil, remain in pan. i suspect its like 16-18 ounces. My original guesstimate was 8-10, but volume is much higher, after testing. To compound matters, there is a little notch on the front inside of the pan hole collar, near the threads. During a drain, the surface tension of the fluid prevents it from flowing nicely through the notch. Basically the fluid bulges into the notch toward the hole but doesn't start flowing out because its stuck in the notch, leaving probably a few more ounces than 16-18. So a dryfill of oil is about 5qt because this equals the wet fill (4.4qt) + 18oz remaining in the pan.

My original interest in this "issue" stemmed from a video, showing some guy doing a head gasket swap, pulling pan, and showing 16 oz of slop/sludge in there. I wondered, is that common under a normal running car? Sludge is probably heavier than oil. if I leave 16 ounces of sludge in pan after oil change and it dilutes with fresh oil, but still contributes to engine wear and caramelizing of the rings, could it be important to get that sludge out of there? Well, I don't have evidence now, and supposedly there isn't a lot of sludge in the pan bottom - usually. But.... I have a OCC installed on one prius, and I collect no oil - just a layer of oil-water and then another layer of most likely water. See attached pic. This means if coolant leaks, oil in crankcase will mix with it over time, forming this odd mixture, which should probably be completely evacuated - i.e., drain oil pan completely. So I endorse georgina's original proposal.

Draining completely during oil change: 16-18oz is about 10% of the total oil, and if its dirty, after ten changes that would be roughly equal to ignoring one 5k change after 50k (if you do 5k OCI). or one 10k change after 100k (if you do 10k OCI). in other words, the particles in that residual oil would contribute to wear in the amount of 10% of normal, over the life of the car. Another way to look at it: if your engine dies at 140k, it could have made it to maybe 154k for example; 200k, and you are looking at another 20k miles. Additionally, if metal particles sink to the bottom of the oil, then that last 10% is going to be the worst 10%, so it might actually equal 10-20% in true damaging ability. My current thinking is that if its easy to extract that last 16oz, why not do it? Oil is cheap and engines are expensive, right? Its easy to say it wont hurt the engine to leave, but then why change oil? and to what amount is it not going to hurt the engine? I believe this is another Prius design flaw, which, if corrected could extend the car engine life another 5-10%. Thats a big win, if you look at 500,000 cars sold.

Drain Plug position: Why incorporate a design flaw into the design? The position of the plug has been accurately posted. Its to the back and "tucked" up behind the pan at about 45 degrees. My feeling is Toyota did this to avoid the rare occurrence of a rock or debris smashing into the bolt and potentially degrading its quality, resulting in an angry owner on a forum like priuschat saying how stupid it is to put an oil drain plug facing the bottom of the car. So they made a trade off.

Drain ideas: Mendel posted a suction bottle with about a 1/4" OD tube. Thats a good idea, but that tube angle is not going to get down into the pan enough, and a 1/4" OD is going to be too frustrating. Tilting the car is another idea, but I don't think you can get enough tilt out of it to make it work. I tried to jack up front a bit higher on last weekends oil change and it didn't get extra anything out. So I believe a custom bent tube with at least a 3/8" O.D. is worth trying. it needs to be more of a U-shape, rather than a V-shape.

Pela extractor: I have one of these pela 6000, which I used on my VW's to pull oil via the dispstick tube. Haven't tried it on Prius though:

Pela Products | PELA 6000
https://pelaproducts.eu/pela-6000/

I'm not sure if anyone has experience using that on prius, but this might be a good thing to try as well. Keep in mind, these things can occasionally get stuck on the dipstck tube and then you have a real nightmare on your hand. And yes, some VW's have a stupid engine gravel guard, which is harder to remove than the prius, so that's where the hole idea started. Prius has the same feel, but the guard is relatively easy to remove.

Magnets in the Pan: I think the Prius rings, cylinder and block are aluminum, right? If so, a magnet wont help much in getting a fair amount of the common wear particles. The dealer tried to tell me there was a magnet in the pan, but I forgot to check before mailing my pan off!

in the end, I'm thinking, create a suction bottle with the correctly-formed suction tube to just pull that last chunk of oil out. If its easy, its probably worth doing. So use mendel's suggestion, but we need to get a more u-shaped and thicker tube. If I can get another pan to test, ill probably try to fabricate something.

 

Get a bottle sim to the pic I posted, then push on an extra piece of tubing. Rigid wall tubing tends to have a curve, being dispensed from a roll: take advantage of that, to orient that curve towards the bottom of sump. Also cut the end of tube diagonally, to parallel the sump bottom.

 

Or get some thin copper tubing (fridge line?) and bend it into optimum elbow, using one of those tube bending tubes to prevent wall collapse.

 

I like attaching a bigger tube to the suction bottle idea. some ~3/8" thicker wall polyethylene tubing duct-taped to the suction bottle tube. And yes, cutting the tip to the correct angle is another good one. Just make sure the tube is securely fastened to the suction bottle so it doesn't fall off in the pan! LOL

The hole diameter looks to be about 1.1cm, so max size OD tube would be about 7/16" if it didn't have to bend to reach. So I think maybe a 5/16" OD max, or something like that.

 

They may have had some reason behind. It’s made of sheetmetal which has limitations but that cannot be the reason. Checked Honda 20A2 pan and its casted and drains completely.

 

????

 

You mean they designed it accidentally so that it wont drain completely? No.. 100years ago that might have happened. But not today. If you look carefully, even that Honda pan has a recess in the center. That’s not there because of human error

 

???????????

 

Btw, it appears all modern Toyotas have this kinf of oil pan. Just checked Camry pan and it appears to leave even more residue to the bottom.

I’ll be visiting dealership next week to get discs replaced. Their bubble gum shall surely stop when i tell them the findings

 

Happy Fall weather folks. I took advantage of the not-too-hot, not-too-cold weekend to do some oil changin'. I decided to risk a bit and bust out the Pella 6000. See pics - it's basically a manually-operated oil vacuum-pump for marine engine oil changes. Since you cannot jack up a boat to drain the oil, this system is designed for top-down oil "drains". I used it in my old golf diesel, which had a similar frustrating engine bottom cover, as the Prius; but the golf oil filter was top accessible. So in the golf, I would just pull the oil out the dipstick tube, using the Pella 6000 extractor (with its flexible tubular "dipstick"), change the filter from the top engine bay. and never have to crawl under the car!

Anyway, moving to the Prius, I decided to make some measurements and do an experiment. My big concern with the Pella is primarily: will the extract-tube get stuck in the dipstick tube, requiring a big engine repair to extricate it. There can be some sharp internal edges and corners in the block; and the extract tube is much thicker than the thin dipstick. Also, the extract tube is coated in some sort of rubber with a metal core, meaning it's going to be a big pain to pull out if it does get stuck. So having said that, I said "what the hell" on the older 2010 and gave it a try today.

WARNING: if you do this on your car, read my poor-man's tips/advice - keeping in mind, that I'm not a professional auto-mechanic, and don't want to take any liability for issues. And no husband wife jokes here!

1. Lube up with oil, the Pella extract tube very liberally.
2. Insert the tube slowly and pull back every 1-2" to make sure you have some backout options - at each point down the "dipstick tunnel".
3. if you encounter any harsh stopping point, don't push the tube farther, as it could flex and curve in the block/pan area, but then could be potentially stuck in there around a tight bend or milled out corner of aluminum.
4. Having looked at the inside of a pan - see prior pictures - you can see, that the extract tube will probably not get hung up on the pan.
5. If the tube does get stuck in the engine block, spin it a bit while trying to pull it out. that works well.
6. if you have the drain plug out or oil filter off, and the tube gets stuck, check those orifices to see if tube popped out in any way. its unlikely it popped out the oil filter recess, but the drain plug hole might be a possibility.
7. Regardless of the "Pella" system you try, use my measurements as a guide. In my case, the O.D. of the extract tube is about 7.5/32", as measured with my crude micrometer. I would like to round up to 1/4" but since tolerances could be tight in this operation, I'm hesitant to do that.
8. Lastly, if you desperately need your car the next day, think twice about doing this, at least until you have a few OC's under your belt with this method.

Having warned the hell out of the process, it didn't really seem too bad! here are some observations, results:
1. First, if you eyeball the route of the dipstick tube from under the engine, where the tube connects to the block, you can see it's a fairly straight shot down to the pan, probably without much internal bending or obstructions.
2. I had the front of the car jacked up 6" higher than the back, meaning there was a pretty good slope on the oil pan toward plug hole.
3. Before doing the Pella extraction, I did a normal drain of oil from the drain plug.
4. The tube went in fairly smoothly. I managed to get it about 4-5" farther than the length of the dipstick itself. See my comparison picture to gauge how much extra tube went in.
5. I did get a little hung up on something near the end of the exploration, but it wasn't too bad and I could pull the tube out relatively easily by twisting it.
6. I managed to pull out some more old oil, even after a drain! This oil seemed thicker than the drained oil, but this is highly subjective. I may have been just happy to pull out more oil this way! At most, I believe this was about 3-4 oz oil, that probably just couldn't drain from the pan, due to the bad design - even with the extra 6" of slope.

Final comments:
1. Why did I only get 3-4 oz of extra oil from the Pella, when the oil pan can hold up to 16oz of oil after a drain? I had the car jacked up 6" in the front, with a big downward slope toward the back of the pan or the drain plug hole. I most likely managed to drain about 10-12 oz of extra oil with this slope. A normal level oil change in a shop is at a disadvantage because the lifts never work the car on a slope. I guess this might be the only one advantage of a DIY oil change with poor-mans tools and ramps, or blocks.
2. Would I do this again? Given that I got only 3-4 extra oz of bad oil, I'm not sure I would do it again. A big advantage I could see would be in doing on-off 5k/10k oil changes, where every second one leaves the filter, but pulls the old oil. in this case, I could do a top-down Pella change at 5k, and then at 10k, drop the plastic engine cover, pull the plug and filter, like usual. Not futzing under the car every 5k would be a big plus to me. Also, if you change oil every 6 months and you only have like 3k-4k miles on the oil, it might be a good idea to just extract it out the top and forget about the bottom futzing around, just for the filter. another scenario I can see is if you are on a trip or just bought a used Prius somewhere: You could take the Pella and easily doing an oil change - probably at a rest stop somewhere with probably a knife and some towels. The last case I can see is if you actually work on the car level and are paranoid about leaving an extra 10-16oz of old oil or think there might be some water in the pan - water sinks! So the last 16 oz, is likely to be water - if you have any in there.
3. Hot/Cold engine oil changes, water!: this experiment got me thinking about water/oil (salad dressing). water sinks, oil stays on top, unless you shake the hell out of the bottle. Given that the pan can hold an extra 16 oz of fluid after a level-drain, you really need to shake up the salad dressing before changing the oil. I suspect this is the real reason Toyota recommends warming the engine up before the drain. So if you have a head gasket leak, you should definitely Pella extract the pan even after changing the oil - or at least jack up the front at least 6-8" to drain as much crap as possible out of the engine.

Hope that helps anyone thinking about this and provided a bit of weekend entertainment. I'll probably turn this into a work document and share it more formally later.