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20w40 v. 20w50: does it matter?

I’m about to change my oil for the first time in 11 years (2,583 miles). The table in the maintenance manual is an arrow that begins at 10°F and extends to just past 100°F. At the left is 15w40, in the middle is 20w40, on the right is 20w50, but there are no lines to demarcate between them. It’s gotten as cold as 10 in Albuquerque a few times, over 100 10-20 times/year.

I suspect it doesn’t matter, especially considering how little I drive. I welcome your opinions - even ‘Get a horse!’

Why change it now , you still have 417 miles left on a 3000 mile oil change.


Does the truck have 78k or 378k?
Has it been driven 2583/11 miles yearly?
Or has it sat for 11 yrs?
I would use 0-40 myself. Better fuel economy

Huh? What difference does fuel economy make for 250 miles a year. More gas would be used just starting it each time than actually driving it. At any rate, ten degrees isn’t all that cold and 20 I think should not be a problem so I’d probably go for the 20-40.

It’s the hot-rodder in my soul.


2,583 total miles over than 11 years. I drive it most years, though it has sat for more than 12 months occasionally, with nothing but a hard start ever manifesting. A battery booster eliminated those.

The manual only recommends 0 for temperatures below 10°F.

The 20 was for sure; whether 40 or 50 is my question.

That’s why I said 20-40. 30 used to be common and then sometimes 40, but 50 is pretty heavy in my view, unless you are pulling a trailer in 100 degree temps.

What is it the Buddhists say? Something like: “Take the middle path”? 20W-40.

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I ran 400k miles using 10W40 oil changed every ~7,000 miles and for years fell back on that oil in everything until synthetic became an obvious improvement for automobiles. In my old flat tappet domestic trucks I use 15W40 synthetic because it seems to offer the best of both worlds in that it is synthetic while it has the additives that flat tappets need and is rated for use well below and above the .local seasonal temperature extremes.

I have for years observed that people who pay close attention to climate, oil grades and viscosity usually enjoy a long a relatively trouble free life from their cars regardless which weight they choose. Those are the people who keep up with oil changes and regularly check their oil and among them those who use 0W20 and those who use 10W30 see very little difference in engine life.

I don’t know how to make sense of this sentence. You seem to have written that as long as you pay close attention, it doesn’t matter what viscosity oil you choose.

Then why doesn’t everybody use 0w50? Doesn’t a smaller range oil perform better when used within its temperature range?

Don’t you live in Mississippi? When was the last time it snowed?

I just went to the Mart of Wal. It had no 20w40 synthetic oil, not by any manufacturer, no 20w40 of any kind, no pure synthetic over 30. I bought 10w40 semi-synthetic. My application is undemanding. I went to and see they don’t have 20w40 though they do have a pure synthetic 10w40. I guess narrowness of range doesn’t really matter much anymore.

It’s my Faulkner blood.

That seems odd for a truck this new to suggest a 15W40 oil. I would have suspected 5W30 or 5W20. I don’t know but a lot of Toyotas have gone to pretty thin oil these days.

Honestly you just need to get that old oil out of the engine. 11 years even with barely any miles is TOO LONG. With the use of this truck, the oil type probably isn’t a huge deal. It just needs to be changed so that acids and moisture don’t corrode the engine from the inside out. You probably also want to flush the cooling system and do other maintenance as well. I could see the coolant being quite bad in a truck like this.

I am going to throw out two that I would suggest.

Mobil 1 0W40 European - You can get the 5 quart jugs at Wal-Mart for like $25. This is a great oil for that kind of money. I have always been told this is more like a 5w30 but was branded this way to meet the more stringent European oil standards while keeping in line with US emissions standards.

Rotella T6 5W40. This seems a little thick for some modern vehicles if you ask me but if your truck REALLY calls for 15W40, this is a very good oil for the money as well. This is really on the thick side of the 5W40 specs so be careful. I use it in all my outdoor power equipment and have no issues no matter how hot or cold it gets. The newer stuff with hydraulic lifters seems to really like it. The lifters used to clatter and then overpump on some neglected equipment I got. I would then have to wait for the lifters to bleed down so I could restart the equipment. This went away in short order once I changed to this oil.

And then I guess I will throw in a third… Whatever conventional oil this truck calls for. If it were to suggest 5W30 or 10W30, use the 5W30. Change it at least every 3 years and made sure you run it long enough to get the engine up to temp for a while.

My gut tells me there are all kinds of other things that will need attention as well. The coolant likely needs to be changed and the brake fluid is likely getting moisture in it from sitting as well. There are likely all kinds of little things that need to be done to this truck.

That’s the point. Folks that worry about oil grade tend to change their oil. That’s the important thing, not the exact oil weight used.

In Cycle Guide their ‘ask a mechanic column’ author said the bikes that ran the longest had the owners that were always asking about maintenance. The bikes that died? Their owners only showed up when there was a problem.

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I looked up the suggested oils for a 2007 Toyota Tundra and came up with this page. It looks like they do suggest 5W20 or 5W30 as I would have guessed, rather than a thicker oil. I was unaware Rotella T6 now came in 5W30 but that is a very good oil so would have no problems using that one if you feel the need.

Get it changed!

Those who only show up when something dies are typically my worst customers. These are the people who want to spend the least amount of money but end up with a more expensive bill because they neglected their stuff. Then they complain to me about the price but it is their fault for causing the failure in the first place.

The people who are willing to have me service their stuff once a year are good. They are willing to pay and routinely spend LESS than those who are not willing to pay.

Remember I work on computers for a living but the same applies to cars as well.

I had a medical clinic that got “hacked” recently. They had no security software and their systems, including their main server had the admin account wide open with no password. It had been this way for YEARS and then got ransomed. I suspect hackers were mining the system for info for a while and then once they were done, decided to ransom it.

They were like “This can never be allowed to happen again.” I told them all the things they needed to do and it was going to be several thousand dollars. They didn’t want to replace the old Windows XP systems that had been upgraded to Windows 7 and 10. They didn’t want to pay for any other forms of security. They didn’t want to pay for any better forms of backup. The old systems were so slow that installing security software bogged them down to a crawl.

They paid me but treated me like I was trash. They were mad that they had to type a password to access the server after I worked on it as that was never required before. Somehow this was my fault and I didn’t know what I was doing. I wrote them an e-mail basically stating that this is willful negligence if you allow computer systems such as this to be wide open and unsecured and customer data gets compromised. I never heard back.

They had been using whatever fly by night company from out of town to fix their problems in the past and setup this mess! They have used like 4-5 different people who are no longer in business. I had been out there a couple years ago to fix some small problems and told them that they were grossly unsecured but they did nothing about it. People like this get what they deserve but this could impact their customers due to data breaches so is not OK.

I had a dentist a little like that. I noticed one of their machine was running XP (a year ago). I commented that ‘wow, you’re really open to hackers with that machine’. But unlike your client, he took me seriously and fixed the problem.

Look up HIPAA violation. Willful negligence could mean millions in civil penalties. The EU just passed legislation that makes individuals liable for customer’s personal data…

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It’s snowy?

I went to,, and none of them had 20w40. I guess it’s not a thing anymore. I don’t care, just noticed. There’s 20w50.

That doesn’t make sense unless the vehicle was designed for the equatorial market.

Anything meant to be in mid to high latitudes would be expected to handle temperatures far below 10 F.

Is the your chart on the right page and the left page is missing?