Excellent Chart, TY for posting.
How cold for 10w-30?
- Thread starter Chris142
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Usually zero degrees F. with conventional. Being synthetic, you can go to -10. That is what my manual states for my vehicle.
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I’ve run Motul 4100 Power 15w50 through an Indiana winter in my Subaru that recommends 5w30 and had no problems. Cranking is a little slow, but that’s partially because Subaru insists on undersizing battery capacity. Pretty sure it gets colder here, unless like someone mentioned, you’re up in the mountains. I’d run 10w30 without any concerns. 
The coldest I've started an engine with 10w30, was somewhere in the -36° to -40°F range. That was in a 3rd gen 4Runner with the 5VZ-FE engine, a strong battery (Optima, the good one before Johnson Controls bought them) and Mobil 1 10w30. It cranked a little slow, but started pretty easily. I owned it for 20 years after that. It ran great when I sold it.
I'd use 10w30 in your 1GR-FE without the slightest concern.
I'd use 10w30 in your 1GR-FE without the slightest concern.
If it is the correct spec for that temperature range as specified in the owners manual then I wouldn’t worry about it. If you have ever disassembled an engine you know that a film of motor oil stays on the parts for a long time, more than sufficient for start up while the engine builds pressure in a few moments.
Absolutely nothing unusual noted running dino, synth, or a blend in -20 Fahrenheit conditions from a cold start. 1979 SBC 350 in a yard plow truck.
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When I was in college I toasted my starter in my first car, a 1989 Mazda 323, when it was -7'F. I roll started it to get home but the starter never worked again.
That all said, the starter was likely on its way out. I was running whatever oil my dad's mechanic put in, probably dino 10w30, and it was the 90s so oil wasn't as good.
My 80s dodge 318 plow truck has rotella 10w30 in it and doesn't like it below 10'F, but it's a gimpy POS with direct-drive starter. Your FJ should be fine.
That all said, the starter was likely on its way out. I was running whatever oil my dad's mechanic put in, probably dino 10w30, and it was the 90s so oil wasn't as good.
My 80s dodge 318 plow truck has rotella 10w30 in it and doesn't like it below 10'F, but it's a gimpy POS with direct-drive starter. Your FJ should be fine.
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I ran Mobil-1 EP Triple Action 10w30 last winter in our Hyunkias'. Temps varied in & around Zero degrees here during a dozen or-so Michigan overnights and not an inner engine rattle - nor slowed crank start, all winter-long.
If I abandon my multi-Amsoil Trials after 2024, I'm running that same 10w30 oil year-round in the Kia 2.0 also.
If I abandon my multi-Amsoil Trials after 2024, I'm running that same 10w30 oil year-round in the Kia 2.0 also.
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More concerned about the oil fed timing chain tensioner
In Apple Valley - I wouldn’t worry. Do you get up into the mountains? Does the truck see below zero temps? If the answer to that last question was “no” then run the 10W30.
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To remove any doubt, I ran SAE straight 30wt. in a 5.3 Silverado for years. My son drove it to north TX once when the temps got into the low 20's. If straight 30 handled that, a 10w-30 won't even blink.
For your edification, poor a couple oz sample in a vial or pickle jar and place it your home freezer chest overnight . I find it (QS FS) pours and swishes easily. Should be a piece of cake lubing the CCT.
What 10w30?
My Hawaiian mother in law has a bone to pick with you! According to her, going out when there is snow on the ground causes instant death.
I find it interesting that as one goes down the chart, the oil is thinner at colder temps.
Anyhow. I had 10W30 in my Tundra one summer, come fall I could hear the cranking difference. Changed it. Didn't want to deal with it, but, we can occasionally see -10F in wintertime. Maybe that Tundra had a bad battery (most likely did--but I used it for several years after that, so just how bad was it?). Strangely the 10W40 in my 4 wheeler doesn't impact cranking at all in cold temps, then again I use an over sized battery.
I did have 30 in a lawnmower once, and learned real quick that I could not pull start that when temps got 50F or whatever (waited too long for the last mow). Multi-viscosity only after that!
My guess, you're fine, it doesn't get that cold there, and when it does, as long as you have a good battery, no issue. If your battery is getting older, you may notice it quicker. Me I'd save it for summer use and find something for winter, but I'm in a different clime so what I do isn't quite relevant.
Oils are allowed to slip a winter grade as they age, so 0°F (-18°C) seems like a good limit for 10W-30. With fresh oil -25°C isn't much of a challenge
The oil has to be thinner as the battery becomes weaker, if you want to get th engine started anyway...
It makes sense, I just found it odd, that's all. I mean, they could have picked a viscosity and then held that number as the temps go down. But instead, as temp goes down, viscosity goes down too. Which, as you indicate, is good as the battery's ability to provide amps goes down too.
Now that I think about it, I wonder if the curve for viscosity drop matches the typical curve of battery amp drop... that'd only make sense.
I think the KV100 is an easy obtainable reference for lab work way back 100 years ago; and engine ran open to atm radiator with water at op temp.
What I don't get is the KV40 reference point, why it is not the NIST NTP of 15C which is closer to a recognised ambient.
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