Oil Viscosity Question - 10w30 vs 5w30 and 0w30

[101Volts]

I'm aware that if the oil is a Xw30 it's compatible with the engine. But, it'll cause more wear to have a 10w30 than 5w30 or 0w30 in theory - If the car engine can take it and not leak or burn oil, is there any reason to not use 0w30? I imagine it would make starts - Summer or winter - easier and get to lubricating the system quicker.

[jcp123]

I don't know that the thicker oil causes more wear - there's some consternation over at the Toyota forums over 0w20 being called for in Camrys in the US but thicker oils being called for in overseas markets (5w30 I believe is what many other markets specify for the 2.5l). I do like the idea of a thinner "cold spec" oil in a car; even then I played it safe with Mobil1 which claimed warrantee protection for cars calling for 10w30 and 5w30. What that says to me is that the cold spec can be played with more than the hot spec. Theoretically, any oil is better than none when you have cold temperatures, and it makes sense that if it can be more readily pumped through the engine at cold temps, it's a good thing.

Having said that, I play the cheap-o when it comes to oil for the Echo; a car as beaten up as that one sort of steers me away from spending much money on it. I got my Mobil 0w30 for $3/jug on clearance which was also instrumental in my buying it; I have one more jug then I go back to 5w30, not because I am worried about a "too thin" oil, but because I acquired some other high quality oil at 80 cents/qt.

[Isaac Zackary]

Yep, the "W" cold grade is a bit more flexible than the non "W" number. From what I understand 0W-30, 5W-30, 10W-30 and even straight 30 all have the same viscosity requirements at 212* F (100* C) and 305* F (150* C). But when it's colder is when the "W" grade becomes important.

I have a Chevy Astro owner's manual here with me. It states that for this particular engine 10W-30 is ok for summer use, but not winter use. 5W-30 is fine for all year. But if temperatures are continuously below 0* F then it recommends 0W-30.

[Mustang Dave]

My last oil change in my Mustang (11-15-2014), I switched from Motorcraft 5W-30 semi-synthetic to Mobil 1 0W-30 full synthetic. It appears to have made a slight difference in cold-weather fuel economy. I made it through this past Winter without dropping below 30 MPG.

Also, I switched my truck from conventional 15W-40 to synthetic 5W-40 last Fall. It starts much more easily in the cold, and I've gotten over 20 MPG with it for the first time ever. Oil consumption has increased to about a quart/1500 miles. Not complaining - 295K miles; original engine & clutch.

[Isaac Zackary]

Originally Posted by 101Volts

I'm aware that if the oil is a Xw30 it's compatible with the engine. But, it'll cause more wear to have a 10w30 than 5w30 or 0w30 in theory - If the car engine can take it and not leak or burn oil, is there any reason to not use 0w30? I imagine it would make starts - Summer or winter - easier and get to lubricating the system quicker.

The thing about 0W-30 is that it thickens as it gets colder just like any other oil. At running temps it's the same as any 30 oil, but of any 30 oil 0W-30 thickens less at cold temperatures. So that way for the engine, starting it up at 0° F is like starting it up at 100° F with staight 30. This is a good thing.

I don't see why any car "wouldn't take" a 0W-30 as long as it's recommended to use a 30 oil. 0W-30 still is thicker at colder temps, just not as thick, and once it warms up it's no different than any other 30 oil. I do know a few guys who swear that cold engines need thicker oil for start up protection, so they usually use straight weight oil, like straight 30. I think they should send that to Mythbusters, I personally don't think that makes any sense.

Another "concern" some people have with multi-grade oils is that multigrade oils contain viscosity modifiers which kind of take up space in the oil meaning that now you have another ingredient that supposedly might deture other ingredients from doing their job. A 0W-30 is going to have more viscosity modifiers than a 10W-30. Straight 30 has none. Personally, I really don't think that viscosity modifiers affect the oil's job of lubricating like that.

Another "disadvantage" with multi-grade oils is that they are based off of the lower grade. A 0W-30 is a 0W oil modified to not thin out as much as it heats up so that it becomes the same thickness as straight 30 at running temps. But IF the viscosity modifiers break down then soon you have 0W-20, then 0W-10, then eventually plain 0W, whereas a 10W-30 can only break down into a 10W oil. Straight 30 will not ever break down thinner than 30. Although this is true, you have to really abuse the oil for it to break down like that. This is the reason some race car drivers prefer straight weight oils. Of course they're running 350° F oil temps! With that kind of abuse I can see why a multi-grade oil might break down into a thinner oil.

[RedDevil]

I just had my oil changed.
12000 miles ago I let the dealership put Honda Green Oil in my engine.
It is somewhat thinner than 0W20.
They gave me a bottle with the remainder, and another with the oil that came out - either regular 0W20 or 5W30, as that's what the bill said on the previous oil change.

Viewing the 3 samples shows that the viscosity of the Green Oil has not been changed much over 12000 miles. It is dark as coffee but just as thin as before.
The old oil is just as dark as the Green Oil, but somewhat thicker. If I swirl it round it stops moving just a bit quicker.

I will have these samples tested professionally soon.
But by the looks of it neither oil has deteriorated much.
I got Green oil again, and am confident it will do 12,000 miles again without issues.

[Vman455]

Originally Posted by Isaac Zackary

Another "concern" some people have with multi-grade oils is that multigrade oils contain viscosity modifiers which kind of take up space in the oil meaning that now you have another ingredient that supposedly might deture other ingredients from doing their job. A 0W-30 is going to have more viscosity modifiers than a 10W-30. Straight 30 has none. Personally, I really don't think that viscosity modifiers affect the oil's job of lubricating like that.

This is where synthetic oils come in. I get a kick out of reading posts by people claiming synthetics are "slipperier", or who are sure their engine "runs smoother" on synthetic oil. The benefit is a naturally-wider viscosity range, requiring fewer viscosity index improvers that could break down over time.

Back when I frequented the Viper forums, there was an oil formulator for Texaco and Shell who posted in threads about oil choice (which, as you can imagine, came up frequently there). He ran a 5W-40 or 15W-40 diesel oil, non-synthetic, whatever-was-cheapest-at-Walmart through his Viper (factory fill on the Viper was Mobil1 10W-30 to 2004, then Mobil1 0W-40--a change made not for viscosity, but because of the higher ZDDP in the European oil when API standards changed). I started using Shell Rotella 15W-40 in mine, both the car and truck. Now, I use whatever the manufacturer put in (synthetic blend 5W-20 in my last car, regular 0W-20 now). I think people concern themselves way too much with oil selection when, for most of us, it doesn't matter that much.