Mobil 1 High Mileage oil not ILSAC rated - ok or bad fit for the Prius?

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slickoil

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Have been using Mobil 1 0W-20 on the 2010 Prius with ~146K. Was considering switching to Mobil 1 High Mileage 10W-30 in the future due to oil consumption issue. Then noticed that the only spec Toyota requires for the Prius is an ILSAC rating (manual doesn't specify which one), and that none of the Mobil 1 High Mileage oils have ILSAC approval. Does that mean the oil is a bad fit for the Prius, and that it would be better using a different high mileage brand that is ILSAC rated?
 
Mobil 1 Extended Performance High Mileage is ILSAC rated. [Linked Image] I wouldn't worry about it. Basically what it means is that it's not "Resource Conserving". Likely on the thicker end but still acceptable.
 
Play Twilight Zone music. Believe it or not, I just discovered that myself a little while ago, while reviewing Mobil's again-changed web site. Of course, my Prius is a low-mileage near-new car, so HM won't be an issue for me for a bit. That said, in the 2018 manual, the only oil "qualification" specified is ILSAC GF-5. No mention of SN, SN+ or what-have-you. Just ILSAC GF-5. Now, do I believe for a minute that your engine will explosively disintegrate ten minutes after you fill it with non-ILSAC M1-HM -- no, not for a minute. I'd just side-step the issue, though, by using the EP-HP, which IS ILSAC GF-5. It would be interesting to know why the basic HM lacks the spec, though.
 
M1 HM 10W-30 is a "thick" 30 grade, as it falls under the ACEA A3/B3 specification (HTHS of 3.5). I think this is a feature, not a drawback. ILSAC GF-5 oils are "resource conserving" (usually around 3-3.1 HTHS).
 
Originally Posted by PPWarrior
Have you tried a new pcv valve?
+1 An OE PCV valve.
 
Originally Posted by ekpolk
Play Twilight Zone music. Believe it or not, I just discovered that myself a little while ago, while reviewing Mobil's again-changed web site. Of course, my Prius is a low-mileage near-new car, so HM won't be an issue for me for a bit. That said, in the 2018 manual, the only oil "qualification" specified is ILSAC GF-5. No mention of SN, SN+ or what-have-you. Just ILSAC GF-5. Now, do I believe for a minute that your engine will explosively disintegrate ten minutes after you fill it with non-ILSAC M1-HM -- no, not for a minute. I'd just side-step the issue, though, by using the EP-HP, which IS ILSAC GF-5. It would be interesting to know why the basic HM lacks the spec, though.
The Basic M1 high mile oil has a 12.i viscosity and 100C when new. https://www.mobil.com/English-US/Passenger-Vehicle-Lube/pds/NAXXMobil-1-High-Mileage-Oils The EP data https://mobiloil.com/en/motor-oils/mobil-1/mobil-1-extended-performance-high-mileage
 
looking but never seen M1 extended perf high mileage yet locally. Wally's is my usual checkpoint. got some super-tech synthetic 10-30 high mileage last night, $10 less than mobil 1 similar offerings
 
Originally Posted by Gokhan
It's a dilemma because if it's ILSAC, it means it's a thin oil and it won't help with your oil-consumption issue.
Exactly. If you have oil consumption, choose the HM oil. It has a significantly higher HTHS and "may" help mitigate oil consumption. The only way to know is to try. NOTE: Some oil consuming prius engines exhibit long term success on more viscous oils. There are warm weather prius taxi operators using 10W40 and changing every 5000. I'd choose the M1, 10W-30 HM. Your location is warm enough that 10W-30 is a non issue. Keep in mind that at 60F, a 10W-30 is considerably thinner than 0W-20 at 0 deg F. [Linked Image]
 
Last edited:
Originally Posted by benjy
looking but never seen M1 extended perf high mileage yet locally. Wally's is my usual checkpoint. got some super-tech synthetic 10-30 high mileage last night, $10 less than mobil 1 similar offerings
The M1 EP High Mileage seems to be hard to find at a good price, especially given how much oil the Prius goes through. Anyone know where to get it for a good price? Given that I'm trying to reduce oil consumption, would the EP or non-EP be better? The EP is ILSAC rated, and the non-EP isn't. The Prius manual only specifies ILSAC as a requirement. Did you try the SuperTech in a Prius, or something else? Is it ILSAC rated? I'm not seeing a 10W30 high mileage SuperTech on the Wally World website, though. Do you see it?
 
Originally Posted by PPWarrior
Have you tried a new pcv valve?
I haven't tried that yet. Some other people with the same Toyota Prius issue have replaced their PCV valves. IIRC, it didn't help, but I'll double-check. About how much should a new PCV valve cost with labor?
 
I should have asked this earlier, but have you switched around with different oils yet? My 04 was over 200k, and used no oil when serviced with regular EP (5w-30), but did show some consumption when filled with AFE (0w-30, one try). My experience may be an anomaly, explainable by other, now unknowable, factors but it still might be worth some experimenting around. I was considering the EP-HM for later use, but alas, decided to strike the car from the inventory for unrelated reasons before I got to that. You might just a particular oil that holds its own against your old engine.
 
Originally Posted by ekpolk
That said, in the 2018 manual, the only oil "qualification" specified is ILSAC GF-5. No mention of SN, SN+ or what-have-you. Just ILSAC GF-5.
From a pedantic point of view, that's a fair way to word it. Technically, all ILSAC GF-5 oils are already SN (or SN+) certified. Only the reverse is not necessarily true.
 
Originally Posted by ekpolk
I should have asked this earlier, but have you switched around with different oils yet? My 04 was over 200k, and used no oil when serviced with regular EP (5w-30), but did show some consumption when filled with AFE (0w-30, one try). My experience may be an anomaly, explainable by other, now unknowable, factors but it still might be worth some experimenting around. I was considering the EP-HM for later use, but alas, decided to strike the car from the inventory for unrelated reasons before I got to that. You might just a particular oil that holds its own against your old engine.
I haven't tried any other brands of oil besides Mobil 1. Are there other brands you would recommend? My goal is to reduce the Prius' oil consumption (as much as possible by switching oil) while not risking damaging the engine in any way. Besides consuming oil, the engine runs perfectly, and I don't want to change that. wink
 
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