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MMO Piston soak Prius #4562902
11/03/17 10:13 AM
11/03/17 10:13 AM
Joined: Oct 2006
Posts: 460
Southeast
Rtstrider Offline OP
Rtstrider  Offline OP
Joined: Oct 2006
Posts: 460
Southeast
Hey everyone I'm chasing down a misfire on my wifes 2011 Prius. The issue is oil is getting into the combustion chamber and is coating the plug causing no spark/misfire. P0303 is the code. The plug looks like someone dipped the electrode/threads in a vat of oil. It's coming from underneath the plug so not an easy valve cover gasket fix frown. That means it's one of two things. The valves or the rings. I tried doing a piston soak on cylinder 3 only and still no go. I pulled the denso plug on cylinder 3, poured around 4 oz of MMO, let it sit overnight, came outside the next morning, looked down the spark plug tube, and the piston was bone dry. That means the mmo leaked past the piston. I cranked up the engine (with the plug out on cylinder 3) with a rag above the hole to see if any mmo would splash out and nothing. Is it normal for MMO to leak past the piston in 8 hours or so?

Re: MMO Piston soak Prius [Re: Rtstrider] #4562915
11/03/17 10:35 AM
11/03/17 10:35 AM
Joined: Jan 2004
Posts: 4,471
California
nthach Offline
nthach  Offline
Joined: Jan 2004
Posts: 4,471
California
Prii are known for oil consumption as they get older - Toyota isn't really acknowledging the fact but there's reports of the 3rd gen cars using oil at lower mileages. The 2nd gen cars will start burning oil around the 150-200K mark. I suspect the piston rings and lack of engine braking are causes of this.

How many miles? If you're still within powertrain warranty, might be time to have the dealer document this and do their own oil "consumption" test which involves topping off and placing tamper seals on the oil cap and dipstick for 1000 miles. Rings don't create a perfect seal. 8 hours is a long time, if it runs out within minutes with MMO or any oil you have a problem.

Re: MMO Piston soak Prius [Re: Rtstrider] #4562925
11/03/17 10:43 AM
11/03/17 10:43 AM
Joined: Oct 2006
Posts: 460
Southeast
Rtstrider Offline OP
Rtstrider  Offline OP
Joined: Oct 2006
Posts: 460
Southeast
The car has around 160k on it

Re: MMO Piston soak Prius [Re: Rtstrider] #4562930
11/03/17 10:49 AM
11/03/17 10:49 AM
Joined: Jan 2004
Posts: 4,471
California
nthach Offline
nthach  Offline
Joined: Jan 2004
Posts: 4,471
California
Sounds like she's using oil at that age. Nothing you can really do except find a good used engine from a wrecker(not a pick and pull) or rering the engine. You can try a thicker oil to slow down consumption, my 2nd gen uses less oil on M1HM.

Re: MMO Piston soak Prius [Re: Rtstrider] #4562949
11/03/17 10:58 AM
11/03/17 10:58 AM
Joined: Jan 2013
Posts: 911
California
Kool1 Offline
Kool1  Offline
Joined: Jan 2013
Posts: 911
California
What is the condition of your other cylinders? If the problem only exists in one cylinder, I would possibly suspect a stuck ring and would consider trying more MMO. Check the spark plugs from the other cylinders, if they aren't looking to good, then it's probably time for some major work.

Re: MMO Piston soak Prius [Re: Rtstrider] #4562962
11/03/17 11:12 AM
11/03/17 11:12 AM
Joined: Oct 2006
Posts: 460
Southeast
Rtstrider Offline OP
Rtstrider  Offline OP
Joined: Oct 2006
Posts: 460
Southeast
Hey Kool it's just cylinder 3. The plugs foul crazy quick on that cylinder. The plugs on the others have no issues. Should I do another piston soak with mmo at the tail end of this oil change even though mmo is already in the oil?

Re: MMO Piston soak Prius [Re: Rtstrider] #4562964
11/03/17 11:13 AM
11/03/17 11:13 AM
Joined: Aug 2003
Posts: 741
ottawa
nicholas Offline
nicholas  Offline
Joined: Aug 2003
Posts: 741
ottawa
Try BG 109 or BG EPR <Same product>

I had great results unsticking some audi rings that were seriously gummed up.

Amazon or ebay are your best bet.

Re: MMO Piston soak Prius [Re: Rtstrider] #4562968
11/03/17 11:18 AM
11/03/17 11:18 AM
Joined: Oct 2006
Posts: 460
Southeast
Rtstrider Offline OP
Rtstrider  Offline OP
Joined: Oct 2006
Posts: 460
Southeast
Hey Nicholas I'll try that at the tail end of this change. Right now we are just keeping an eye on the oil level and color.

Re: MMO Piston soak Prius [Re: Rtstrider] #4563030
11/03/17 12:49 PM
11/03/17 12:49 PM
Joined: Mar 2016
Posts: 1,651
Western S.C.
CR94 Offline
CR94  Offline
Joined: Mar 2016
Posts: 1,651
Western S.C.
Probably coked rings and plugged oil drain holes in the piston, same as with many other Toyotas (e.g., 2007-10 4-cylinder Camrys) and others susceptible to that problem. What kind of oil has been used in it? Change intervals?


2011 Toyota Prius now at 94K
1981 Mazda GLC (323) retired at 606K
1972 Subaru DL retired at 190K
1954 Chevrolet retired at 121K
Re: MMO Piston soak Prius [Re: Rtstrider] #4563051
11/03/17 01:08 PM
11/03/17 01:08 PM
Joined: Jan 2004
Posts: 4,471
California
nthach Offline
nthach  Offline
Joined: Jan 2004
Posts: 4,471
California
Originally Posted By: Rtstrider
Hey Kool it's just cylinder 3. The plugs foul crazy quick on that cylinder. The plugs on the others have no issues. Should I do another piston soak with mmo at the tail end of this oil change even though mmo is already in the oil?

In that case what I did was run Lubro Moly's engine flush with the car in maintenance mode for 20 minutes. I then changed the oil with Castrol Edge HM, the oil usage got better. About 500 miles out from an OCI, I ran a pint of MMO and changed the oil when it was time. This time I used M1HM and I saw a marked change in oil consumption.

I think running MMO in the oil will help it do its work longer than a piston soak. The Lubro Moly flush works in the same concept as BG EPR 109.

Re: MMO Piston soak Prius [Re: Rtstrider] #4563056
11/03/17 01:16 PM
11/03/17 01:16 PM
Joined: Nov 2009
Posts: 1,918
Ontario Canada
cjcride Offline
cjcride  Offline
Joined: Nov 2009
Posts: 1,918
Ontario Canada
Rtstrider, did the car get a steady diet of synthetic oil and still develop the oil burning?

Re: MMO Piston soak Prius [Re: Rtstrider] #4563077
11/03/17 01:49 PM
11/03/17 01:49 PM
Joined: Sep 2004
Posts: 7,827
Marshfield , MA
andyd Offline
andyd  Offline
Joined: Sep 2004
Posts: 7,827
Marshfield , MA
Have you done a compression test?


'16 Camry LE STP synth 0w20 and STP filter. the Fridge

1994 Ranger ,the Rat, 5w30 dino, STP filter

'16 Camry SE, Valvoline HM 0w20 and OEM filter
Thick oil is better grin2
Re: MMO Piston soak Prius [Re: Rtstrider] #4563086
11/03/17 02:01 PM
11/03/17 02:01 PM
Joined: Oct 2006
Posts: 460
Southeast
Rtstrider Offline OP
Rtstrider  Offline OP
Joined: Oct 2006
Posts: 460
Southeast
The car was new to us as of March this year. The previous maintanence was all done at the dealer. Since we have had it it's been on mobil1 0w20 for a 10k mile change (dipstick was bone dry but that was the recommended interval I found online), the next 2 changes were bulk oil 0w20 from a mechanic that was troubleshooting this issue for 5k miles, mobil1 0w20 high mileage for 3k miles untouched, piston soaked and ran a pint of mmo for 1k more miles. Oil was drained and it's now on 3.5 quarts supertech 5w30 high mileage and 1 quart mmo. This change is going to be run to 3k max or when the oil darkens (which ever comes first). The first mechanic supposedly did a compression test and said it looked good. The plan was to run mmo for the next couple of oil changes to see if that helps. I don't mind doing an oil flush at the end of this change. I had eyeballed kreen due to previous reviews on bitog but I'm game for bg and lubro moly if those are just as good.

Re: MMO Piston soak Prius [Re: andyd] #4563106
11/03/17 02:36 PM
11/03/17 02:36 PM
Joined: Oct 2014
Posts: 12,582
Idaho
CT8 Offline
CT8  Offline
Joined: Oct 2014
Posts: 12,582
Idaho
Originally Posted By: andyd
Have you done a compression test?
This !


2015 Ford F150 2.7
2018 Ford F350 6.2
Re: MMO Piston soak Prius [Re: Rtstrider] #4563130
11/03/17 03:07 PM
11/03/17 03:07 PM
Joined: Aug 2008
Posts: 21,313
ON, Canada eh?
StevieC Online content
StevieC  Online Content
Joined: Aug 2008
Posts: 21,313
ON, Canada eh?
With that kind of oil showing up on the plug I would suspect the rings are so bad in the cylinder that it would show much lower compression and if it does no matter of quick fix it going to solve the problem other than yanking out the bottom end and putting new rings in. If compression is fine suspect the valve seal is the culprit on that cylinder and that isn't an easy fix. You could try High Mileage oil in that situation.

I also wouldn't use thicker oil especially in a Prius if the engine isn't running all the time. (Not sure if that is the case with your model).


Last edited by StevieC; 11/03/17 03:08 PM.

'18 Dodge Grand Caravan GT - AMSOIL SS 5w20
'06 Santa Fe - 535,000km AMSOIL SS 0w30 / ATF
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