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what is the difference in the oils?

Posted by febc775 (My Page) on
Tue, Oct 2, 07 at 21:45

i was wondering the differences between 10W30 ad 10W40


Follow-Up Postings:

RE: what is the difference in the oils?

about 7 cents a quart, at the corner parts store by me.

RE: what is the difference in the oils?

I've been wondering if I really need to use 5w20 in my engine like it says. Wouldn't 5w30 work just fine on an engine with 140,000 kms?

RE: what is the difference in the oils?

Hi Tim.

In short, NO. But if you really want to dig deeper it depends. Look in your owners manual and see what it says there for the recommended oil. Sometimes a heavier oil will be allowed under certain conditions. For some engines the 5W20 actually already is the "heavier" oil and you may be able to go lighter. One thing to think about is 5W20, as originally specified is at the least a partial synthetic blend, if not a full synthetic.

Just to give you an idea of how complicated this actually gets, some hybrids are so sensitive to engine oil viscosity, that too heavy of an oil can cause a no-start, and a trouble code to set because it looks like a mechanical engine problem to the onboard computer. Taking that into account, you can easily see how someone really could not answer your question in a simple fashion.

RE: what is the difference in the oils?

The difference between 10 W 30 and 10 W 40 is that 10W40 has more viscosity extender.

Somewhere in the dim past of my memory, it seems that a car company blamed 10W40 for some of its cam shaft and lifter failures and recommended to go no higher (with viscosity extender) than 10W30 for most of its engines.

RE: what is the difference in the oils?

Think of it like this

5/20= water
5/30= sugar water
10/30= maple syrup
10/40= cold maple syrup
20/50= karo syrup

Now a new/fresh engine is tight, a older engine will get a little looser.

Now imagine yourself swimming in a pool of all of the above. Its gonna be harder to swim through the 20/50 than the 5/20. Therefore new engine might benifit from 5/20 because its easier to turn in 5/20 than any if the rest. If its turning easier than its saving fuel.

Now another aspect to this, is where you live. Lets say you live in canada where its 10 degrees F, that 10/30 is gonna thicken ALOT, Therefor not getting oil to your upper engine very fast therefore its running without oil up there for a min or so. So in cold climates you would run 5/30 and in warm climates a 10/30 is recomended.

When a engine gets older it might start to use oil, the engine gets looser and the oil gets by the rings. When it starts using oil up the weight of oil.

Thats about a 1/4 of what I could explain to ya but that should be sufficient.

RE: what is the difference in the oils?

The subject of engine oil is far more complicated than just how thick the oil is. Additive packages required by various engine manufacturers differ greatly. Take at look at VW engine oil specs. VW originally listed their "502" 0w40 full synthetic certification as the only oil allowed for certain engines. API SM did not meet this standard, but under the threat of a lawsuit (similar to the one Mercedes lost) VW took a temporary step back and allowed the API SM oil. The result was a very high number of engine failures, specifically camshafts locking up in the cylinder heads.

Rules about oil;

Follow the manufactures guide book for whatever engine you are dealing with.

Pay attention to not just the API/ILSAC ratings but the actual O.E. specs.

Use the temperature guide in your owners manual to choose the weight of oil you should be running. Run that weight (those weights) of oil for the entire lifetime of the car. It is NOT OK to go heavier than the spec as the engine ages. Sure, cylinder wear is likely occuring, and you could use more oil. Check it and add as required! Your camshaft bearing surfaces in the cylinder head should not be wearing, too heavy of an oil could result in excessive wear and a failure in this area.

Change your oil more often than just when the maintanence light comes on. 3mo/3000 isn't broke, stop trying to fix it. I see a lot of engines fail for lubrication issues, where people are waiting to change the oil when the car finally tells them to, that could have been prevented by another $100-$200 worth of oil changes. I also see warranty companies that bounce their claims at the slightest hint of the failure for the owner to maintain a car.

With today's engines that have Variable Camshaft Timing, which is engine oil controlled. Variable Displacement, "VTEC for you Honda/Acura fans",.Cars with complete cylinder cancelling, (Dodge Hemi 5.7 , Chevrolet's V-8 5.3l and V6 3900 LZ8, Honda's 3.5l, and the Accord Htbrid) all of which are operated by solenoids that control oil to rocker arm pistons, or to the lifters which when activated cancel cylinders reducing the engines displacement, for both fuel economy, and emissions controls. I can't stress enough how important it is for the engnie oil to stay clean, as well as be the correct viscosity.

I don't have any more time to spend on this subject right now. Grab some books, and start reading. Real ones, not those written by the "25,000" oil change group. They have never been correct IMO and in this day and age, they couldn't be more wrong.

RE: what is the difference in the oils?

To a normal car person man, all you said right their is going to confuse them more than help. Im not saying your wrong, just gonna complicate how they think. Thats why I kept mine simple.

RE: what is the difference in the oils?


What is a normal car person? How does being accurate and correct confuse more than help?

In your first response you tried to pass off tips like (quote)"When a engine gets older it might start to use oil, the engine gets looser and the oil gets by the rings. When it starts using oil up the weight of oil." as good information. If anything is going to confuse somebody it's advice like that!

Some of what you wrote is just accurate enough to be believable from an uneducated point of view. Sure the higher the second number in an oil weight viscosity, the thicker the oil is, and ambient temperature does play a role in pour point as well.

Try this, Take a quart of 10w40, 0w40, 10w30, 5w30, 5w20, and 0w20 each and put them in a freezer for about 6 hours. (-5 to 5f).Then time how long it takes to pour the quart of oil out of each bottle as you take them out of the freezer. Report back on exactly what you find.

Repeat the test with the oils at 100f. See if you can really measure a significant difference between the oils.

The actual testing is done by having the oil flow through a specifically sized orifice.

The first number is often confused as how fast the oil will pour at 0f. It actually has to do with the friction that the oil has at that temperature compared to a straight weight oil. 0w40, 10w40, 20w40 are all 40 weight oil. They have significantly different friction charateristics at 0f.

Lastly, don't take offense to the fact that a subject as simple as oil is far more complicated than the "average car person" understands. After 30+ years of fixing cars, I still study this subject all of the time, as well as everything else that has to do with today's cars. The information about the VW camshaft problem is something I just read about in the last three days. Recently I had a car in for an emissions failure, a 2003 Nissan Murano. The failure was catalyst efficiency montior, and variable camshaft timing (VCT) system failure. Essentially, the VCT problem is because of a lack of proper oil change frequency. The engine is sludged up, and the only correct, complete repair is a full teardown, clean and rebuild or else simply replace the en gine. The catalyst problem is the convertor has failed, because of engine missfire related to the camshaft timing control problem. If the guy had listened to real technicians, giving out correct information he would not have been in the situation of having a car just short of being paid off and needing some $6000.00 in repairs!

So if it's too complicated for someone to understand how to properlly maintain a car, then they have choices. One is to find a real shop with a good technician and follow the guidence they give. Or they could try and simply run around looking for the "best price" hoping they can find both a bargain, as well as someone that takes auto service seriously enough as a career to invest the time required to truly know all of the details required to get it right.

Or of course, they can believe all of the 1/2 truths out there, and simply believe that if a guy has a wrench in his hand he is uneducated, and probably a rip-off. Then they can rely on information they get off of the web, and go about vehicle ownership, just like the guy with the Nissan.

BTW, the old pay me now or pay me later commercial? There is a twist. The guy with the Nissan simply traded it in, took a beating on the cars value and dumped all of the negative equity into his new Honda. Hope he is happy with that $600.00 a month payment he should never have needed to make......

RE: what is the difference in the oils?

The higher the number the thicker it is. Thicker oil makes a better seal and lubrication, but it takes longer to heat up and may create too much oil pressure (gaskets break).

Ambient temperature and engine design affect what type you use.

In Australia, older cars use 20w40 or 20w50. You can get 20w60 but I wouldn't use it because it'd blow your gaskets, okay maybe on an old Holden or Austin engine.

*In theory* an older car (particularly if the engine is reconditioned) works better with thicker oil because the oil passages and clearances are wider, but then the gaskets are weaker too so not necessarily.

IMO I don't think 10w40 or 10w30 would make that much difference (esp. if you live in an area that doesn't snow).

RE: what is the difference in the oils?

Mr. John g:

I am a 'normal' car owner. Please consider this:
I live in Iran. Almost all of the mechanics and oil change personnel in here are uneducated. At most, they have a diploma. Since none of them speak English, they can't even read the labels of oils to understand for what car or what climate it is recommended. I however do speak English and can search on the web. So for me, as an IT Technician, it is not possible to "find a mechanic who knows what he's doing" as they all have "heard" what is good and what is bad. Generally speaking, more expensive oil is better (that's the mentality here), and you go with your own budget. At the moment, there are 4 major brands of oil sold in Iran: Total, Castrol GTX, Shell Helix and another Iranian brand. My car, Peugeot 206 recommends using Total. Today, when I wanted to change my oil, I asked the mechanic and he said well we have 20/50 (he refered to it as "the red can" and 10/40 "refered to it as grey bottle") which one do you want ?! Since I don't have the time to read hundreds of pages on oil properties and viscosity and how car engines work, I used the internet to find a quick help for this. vahomeowner's answer was basically what I needed. I believe I have made the right choice with getting the grey 10/40 Total oil as it's going to get cold soon and it helps having a thinner oil in the sub zero (centigrade) degrees of the winter months in Tehran. Your complicated answer, and mentioning "find a good mechanic" cannot help, sorry ! Especially when you are not in the US of A, and you know, there are others in other parts of the world....

vahomeowner: Thank you for a simplified answer. It was spot on.

RE: what is the difference in the oils?


You need the internet to choose the wrong oil for your car, because the mechanics in your country are uneducated?

Next time try looking in the owners manual. But then again just think, with your education maybe you should become a mechanic. Surely you would do better than all of those other people. People just like me, people with only a high school diploma........

RE: what is the difference in the oils?

Want to know a little about engine oils? Start here.

Here is a link that might be useful: Valvoline Oil website

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