I'm starting to see alot of newer cars using 5w-20 instead of the usual 5w-30. Anybody know the reason for this switch?
Is it for fuel economy?
Is it for fuel economy?
Newer cars with 5w-20
- Thread starter RockerGuy
- Start date
invictus43
Well-known member
No.
care to explain?
invictus43
Well-known member
Ok. I think people remember "the old days" when it was the right thing to do to run 20W-50 in their race engines. Times move on. Thinner oils have better additives than older oils ever had. Engines are built with tighter tolerances and better materials and allow the use of lighter oils. Most engine wear occurs at startup..thinner oils flow better at startup (the high number in the viscosity). Oil also cools..modern engines are better at getting rid of heat making the oil's job easier. Better fuel economy is part of the equation. I think the important thing is to respect the change interval, including the time interval if you're not driving that much, and don't worry about using thinner oil edit: as long as it's the viscosity specified by the manufacturer. These motors still go a long way, no worries.
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The engines have been designed to work with that viscosity. For one thing, to my knowledge, they're for the most part using roller cam followers to eliminate the camshaft / flat-tappet lifter sliding interface that many engines have historically had.
0w20 or 5w20 are NOT suitable to be used in engines for which they were not originally specified.
I have a VW diesel engine which requires 5w40, and even 5w30 has been found to drastically shorten camshaft and valve lifter lifetime (and quite a few people have found this out the hard way). Flat-tappet lifters on that engine. The 2009-onward engines have roller cam followers.
Honda published an SAE paper in late 1990's that outlined the fuel economy benefits of 0w20 and the corresponding increase in engine wear as a result of reduced film thickness.
For all intensive purposes, the additional wear was negligible - as long as the engine was designed to work with the grade of oil.
If you look at a stribeck curve, the engine manufacturer has to design the bearing diameters to ensure that the film thickness is sufficient at worst case scenarios. In this case it would be high load, low speed, and high oil temperature.
Running a higher viscosity oil will move you further to the right on the stribeck curve, and will only be of benefit under conditions that elevate the oil temperature.
**** EDIT *****
Something like this came up recently at work - a customer`s engine was showing good (low) friction from the cranktrain, but excessive friction from the valvetrain. The issue was narrowed down to the cam bearing diameter being incorrectly sized. As you increased oil temperature it caused you to move to the left (from minimum friction) on the Stribeck curve. Bad news for friction and bad news for increased cam bearing and journal wear.
In order for this engine to be optimized for a lighter grade oil, the cam bearing diameters would need to be resized to reap the benefits.
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Here is the paper, http://papers.sae.org/1999-01-3468/
invictus43
Well-known member
Partly. The bearing journals require an oil film to function correctly. The bearings require pressure to maintain that film. If the clearance is larger, you either need more pressure or thicker oil to maintain the cushion. If you tighten the clearance (which is easier now with better manufacrturing and materials and more uniform cooling) you can use thinner oil. You still have to have enough oil viscosity at the temperature range the engine will work in. The designers consider all these things and give a viscosity rating.
I believe this to be incorrect.
Honda for sure, and I'm positive Ford too, and others, once specified 5w30 for their engines, then the following model year, with the exact same spec engine suddenly was listed for 5w20 oil.
I'm very sure that this was done to eek out every last mpg from the car by going with thinner oil, which in turn helps the automakers CAFE rating, to offset their penalization when they produce bigger gas guzzling but more profit making trucks. I won't get into the CAFE thing, but anybody who follows auto politics will know what Im talking about.
EDIT: google search shows plenty of Honda/Acura owners whose engines called for 5w30, but when visiting the dealer for an oil change, being told that 5w20 was put in, because "thats what honda recommends".
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Maybe VW, but for Honda if the engine originally called for 5w20, 0w20 can be used in its place.
Then that is an engine for which 5w20 or 0w20 is originally specified - just maybe not for your model year.
You are missing the point. I still say, BE CAREFUL. The engine might look the same on the order sheet but you don't know whether they've made detail changes to internal clearances. The other thing that may have happened is that they may have done wear testing and determined that, although the life would be shortened, it would still last longer than the warranty period. Is that what you really want ...
If your owner's book says 5w30 then it is always safe to use that. If it says 5w20 or 0w20 then it is safe. If the manufacturer has issued a TSB or other document stating that 20-weight is permissible (see chart above that Jay posted) then it's safe. But if there's no indication whatsoever of 20-weight being permissible in a given engine family then DON'T USE IT. That's my point.
5w20 + VW camshaft and flat-tappet lifters = bye-bye camshaft and lifters.
Think about it. Are the manufacturers going to:
A) Keep an eye out for every opportunity to reduce MPG and decide to use new technology that allows the design of engines that run on lower viscosity oil?
- or -
B) Design an engine around 10W30 and then when productions starts they just up and decide to specify 5W20 to shave a few fractions of MPG and cross their fingers that reliability doesn't suffer too much? OK, maybe Chrysler.
invictus43
Well-known member
It's funny cuz it's true!!! :-D
Thanks
That brings about another topic of discussion. I've also notice some cars coming with "lifetime" fluid in their transmissions, some are even sealed. To me, there is no such thing as lifetime fluid. The last car I drain with lifetime fluid in their transmission, there were metal filings in there. After 100k km. Sometimes their lifetime might mean, after the warranty period.
