do 5w-30 users ever with to thinner oils?

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Originally Posted By: Miller88
Originally Posted By: Shannow
Originally Posted By: Miller88
I ran 5w-20 in my Jeep 4.0 once. It was just as noisey as it usually is.


What was the MOFT (minimum oil film thickness) between the two ?


I don't think that matters much.


Given that MOFT is what keeps bearings separated, I guess noise is really the determining factor then...roll away...
smirk.gif


As to oils shearing...you don't know what the HTHS loss is when the KV drops...I'd love to find out, but it's probably not linear with KV.

And seeing as you brought up 30s becoming 20s (rare), what about when the 20s shear out of grade ?

Your premise fails.
 
I guess it is probably safer to up one grade than down one grade. You either stick with manufacturer recommendation or up one grade in warm weather.
 
I'm not going to run 5/20 in my motorhome(Ford V10) in 100+ temp's going up 24% grades. My brother killed the lower end(mains) in his motorhome(same engine as mine) going down the road in high temps(104) he was fighting head winds at the time but that should not hurt the engine.

ROD
 
Unless the manufacturer back speced it I wouldn't even think about it unless I used something like RedLine Oils since they are just a bit thick for grade and are very shear resistant. But in the end, it's just not really worth the risk.
 
I don't trust back spec'ed recommendations myself. Manufacturer's get extra CAFE credit for back spec'ing older cars that are not under warranty anymore.
smirk.gif


I don't think they are looking out for you.
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It's not like 5w20 didn't exist when those cars were built.
 
Originally Posted By: KCJeep
I don't trust back spec'ed recommendations myself. Manufacturer's get extra CAFE credit for back spec'ing older cars that are not under warranty anymore.
smirk.gif


I don't think they are looking out for you.
21.gif


It's not like 5w20 didn't exist when those cars were built.


Considering how long and slow manufacturers react to some things, it does surprise that even with 5w20 available, many manufacturers just were not as nimble to convert (and since CAFE contributed to DECLINING fuel economy from 1989-2004) there was no real incentive to use a lighter oil. So even with carry-over, many engines can use lighter oil after 2004 because of the delay from large organizations. Heck, even the Windsor engine was hanging around into the 2000s. While lighter weight oils might only offer fuel economy, I just do not see a lot of significant evidence that the lighter oil will result in decrease longevity... especially for a general consumer. For fleet use, the fuel economy bump (depending on the mileage) would definitely off-set any perceived maintenance cost. I would not be running out to use Xw20 in a Xw40 application or in extreme environments (say desert 110F+), I have no issue running 5w20 in my gasoline transit vehicles(cutaway E350/E450)despite hills (over 20%) and stop-go duty for 14 hours a day.

Considering the legal environment around manufacturers (even for vehicles out of warranty) the back-spec recommendations are likely accurate to a point but like all things, the consumer has to figure out what works best for them. I will not pour Xw20 in my 1ZZ, but there are no issues with the EJ (not back-spec'ed) with going thinner.
 
There's no problem running a 20 grade oil where a 5W-3O or even heavier grades are specified and many members do.
Manufacturers factor in a large viscosity reserve to deal with extreme conditions that can
result in very high oil temp's but since most users never see oil thinning high oil temp's most would benefit in using the lighter grade.
The key is how to know for sure, at least for one's piece of mind, and the best way I know to do that is by installing oil gauges.

But if you don't want to go to the bother of installing oil gauges and you drive conservatively;namely, no WOT when the engine is fully hot on a hot day then yes I'd say you can safely use a 20 grade where a light fuel conserving 5W-30 is specied, just keep the oil at the maximum level on the dip stick.
 
Your point does bring to mind the old Audi, where the manual allowed everything from 5w-20 to 20w-50 (plus monogrades). Now, all of a sudden, we are brainwashed into believing that Vehicle X must have 5w-30 year round and Vehicle Y must have 0w-20 year round, and any deviation will result in dire consequences.

Going a bit thicker doesn't hurt, nor does going a bit thinner under the right circumstances. 0w-20 would be a bad idea if I were towing with my F-150, as would SAE 40 in -40.
 
Isn't that akin to fitting retreaded tyres, and having to install a sticker on the windscreen to inform any alternative drivers not to exceed 140km/hr
 
It may be 'old habit' but i have no issue going one grade up, but don't have the nerve to go one down. Unless specified by the OEM.
 
Originally Posted By: edwardh1
Trend seems to be to thinner oils - is that just an oil trend or did the engines that now use 0-20 oil have different features?
do people using manufacturers speced 5w-30 oil ever switch to the "newer? thinner 0-20 oils? or are the savings too small and the risk too high


My 4Runner V8 calls for 5W-30 from the factory. In eight years, through freezing cold Colorado winters to scorching hot summers, including towing a 2500 lb sailboat on trailer...

I still run the same weight oil, synthetic... formerly Pennzoil Platinum, now Mobil EP.

Runs great, no burning oil, 7500 mile OCI while under warranty... now 10K with EP.

Don't see any need for a 5W-20 or 0W-20 or 0W-30 weight oil.
 
I'd run 0W-20 it in my GM 3.1 60-degree V6 if I could. Yes, the one that went 40k miles on 0W-30. But the cost is so overwhelming here in Canada that I hardly see the point.
 
Originally Posted By: CATERHAM
There's no problem running a 20 grade oil where a 5W-3O or even heavier grades are specified and many members do.
Manufacturers factor in a large viscosity reserve to deal with extreme conditions ...


Even so, agree with you, but then why manufacturers recommend a 20 grade oil (only) in the US while for same vehicle/engine combo they have recommended a 30 grade up to a 40 grade oil in Asia and Australia ?

If one goes to extend oil change interval in an engine which allows both 20 and 30 grade oils, would you rather use the 20 grade for extended miles intervals ?

thanks
smile.gif
 
My viscosity reserve is the HTHS viscosity. If a manufacturer specifies a certain oil grade or a spec that has to meet their minimum HTHS spec, which by the way was developed to simulate the severe operating conditions, there is a reason for that.

Since pretty much nobody, outside the manufacturer's engineering department, knows the exact safety margin for their designs for the specific operating conditions, anybody speculating on how large or little the said margin is, simply blows a bunch of hot air to artificially boost their credibility.
 
Originally Posted By: KCJeep
I don't trust back spec'ed recommendations myself. Manufacturer's get extra CAFE credit for back spec'ing older cars that are not under warranty anymore.
smirk.gif


I don't think they are looking out for you.
21.gif


It's not like 5w20 didn't exist when those cars were built.

I agree.
 
Twice in this thread it was stated as fact that "back spec'ing" can create CAFE credit. Since CAFE metrics are calculated for a given model year and credits can only be applied three years back or 5 years forward, I don't see how "back spec'ing" today can provide any benefit. Can someone explain how this could work or provide some sort of reference to validate this concept? I would like to think that people aren't just making stuff up...
 
Originally Posted By: suspiciousmind
I've twice bought 0-20 for my '90 miata but I can't find the courage to run it.

I'd never run 0w20 In a na Miata. It specs for 10w30 and some even use up to 20w50 on the Miata.net forum. Il stick with 10w30 syn. Love my na too much
 
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