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Discussion Starter · #1 ·
I know we have discussed oil change intervals and filters but I could not find discussions on viscosity. My manual (which is usually my bible) states I should use Ford Motorcraft 5W -20 engine oil. My Ford dealer said "things have changed since my manual was printed in 2014". I have a 2014 Mustang Convertible (premium and pony packages) with the 3.7 engine. The dealer invoice stated Ford Motorcraft 0W-20 "full synthetic" was used. I asked for an extra quart and they sold me 0W-20 Mobil "full synthetic" and said that is what they are now using. So - did they use Motorcraft "full synthetic" or Mobil "full synthetic" and does it even matter which "brand" they used? My opinion is that Mobil "full synthetic" is lower quality that Mobil 1 which uses higher synthetic base components. There are 43,000 Km on the engine and I have driven 1000 Km since the oil change and there is no sign of oil usage. There are no audible sounds that concern me like clacking tappets etc. Any thoughts appreciated.
 

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I dont see any harm using 0W-20 instead of 5W-20. I would guess the M1 is full synthetic. If your car has been historicly serviced with Mororcraft 5W-20 it is synthetic blend.

I think i would have pushed the service department for more specifics about the oil viscosity change. His answer sort of sounds dismissive the way you quote it. Have him show you any Ford 3.7 requirement calling out 0W-20 . Have him bring it up in his system.
 

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With any VCT engine I would only use what viscosity is recommended in the manual. The VCT components require a certain viscosity to operate correctly and reliably as designed. The "things have changed" line from your dealer is definitely not kosher and I would not go with a thinner oil if I had to choose a different weight. They should have plenty of Motorcraft 5w20 there since it's not like Ford isn't making 5W20 anymore. It is/was used for most Ford vehicles produced in about the last 25 years. This isn't like it's an engine coolant reformulation. This is a basic oil viscosity requirement.
Also, why they sold you Mobil oil at a Ford dealer is beyond me as it should have been Motorcraft but something there isn't right imo. I doubt the thinner oil will hurt anything but it isn't a good idea to use it imo. I also believe that the Mobil Full Synthetic is not the same quality as Mobil 1. The Mobil 1 is advertised as an advanced formulation guaranteed to 10k miles and the Full Synthetic just says Outperforms conventional oil and provides guaranteed protection that is 1.5X longer than our conventional and synthetic blend oils. It doesn't exactly inspire the same confidence as Mobil 1. Having said that I'm sure it's just fine and better than any synthetic blend but the weight is the real issue.
Like ONEZ ST said you should have asked him to show you what changed and where it specifies 0w20 in your engine now which to my knowledge has always specified 5w20. It sounds like a bunch of dealer bs to me. Maybe they ran out of 5w20 or someone there that buys the oil can buy the 0w20 Mobil stuff for dirt cheap. I would call another dealer not affiliated with them and ask what they would use for an oil change in your car. If they say Motorcraft 5w20 then you know something fishy is going on at your usual dealer.
 

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I have not heard about 0W-20 for these engines, but I'm not surprised because it has been used in other cars for a long time (my 2006 Camry uses 0W-20)

the 0 means it flows like at traditional 0 weight oil when it is cold; the 20 means it flows like a traditional 20 weight when hot -- so it should give roughly equivalent protection to the engine as the 5W-20, but flows better on cold startup

IMHO any full synthetic should be fine; I like the Mobil-1 Extended Performance because it uses a better base stock; some others still have a bad taste in their mouths from the controversy when Mobil first introduced Mobil-1 many moons ago

I wouldn't worry about the oil viscosity affecting the variable valve timing or anything else; oil always changes viscosity as it goes from cold to hot, and these engines operate fine with a wide range of viscosity; for example the road-track cars (track pack, performance pack, GT500, GT350, ...) recommend using 5W-50 using the same cams and everything and they operate just fine.

Personally I would probably stick with the 5W-20 for normal duty, but I wouldn't stress over the 0W-20
 

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Also, from what I understand (from threads on Bob is the oil guy's site over the years). Mobil 1 was made from cheaper stock than the original, starting in the late 90's,
early 2000's. Mobil 1, extended performance, (usually 2-3$ more for 5 gallon jug) is supposed to be closer to the original "quality" of how Mobil 1 was made when it first came out.

I have run 5W-30 with the blower for about 6K miles and the track pack cars (S197's for sure, not sure after that), recommended
20W-50 for track days, so valvetrain is not sensitive to thicker oils. Not sure about thinner.
 
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By virtue I think all oils can be called mystery oils.

OEM's in general are using Oils with the lower numbers. Camry for years used 0W-20 but the newest gen 2.5L uses 0W-16. But when the wife takes her 2014 in for servicing they still use the prescribed 0W-20.

This is not a plug for BND, but if anyone is interested in custom oil blends, fuel additives, or transmission fluids, reach out to them. For no other reason than learning something new . . . a new perspective on those fluids.
 
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Discussion Starter · #11 ·
So here's what I was told today. I telephoned 16 Ford dealerships today in three nearby cities. I did this because my latest maintenance invoice (wife took the 'stang in) read: LOF Change Oil - Full Synthetic ..... 6 CXO OW-20 LFS6 Motorcraft SAE 0W-20 + 1 FL500S Filter Assembly. The dealerships were split about 50-50 as to recommending Motorcraft 5W-20 or 0W-20. Some said the Motorcraft 0W-20 was likely Mobil "full synthetic" 0W-20. *****One advisor said "at one time" he thought Ford's VVT was partially actuated by oil pressure and that changing viscosity could alter the timing. Another guy said that was no longer an issue and the 0W-20 would be better BUT he would still change it at the interval for 5W-20 and NOT stretch-out the mileage. He said if I did that the Motorcraft/Mobil "full synthetic" would be "plenty good enough" and there was no advantage to spending the money for potential benefits of Mobil 1 unless I tracked the car or used a longer change interval. Always fun asking advisors isn't it - that's why I prefer the much more reliable advice found on THIS forum! :)
 

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The opinions don't surprise me at all but you really will be fine using either weight oil. Its probably what Braindead said. The dealership probably buys bulk and chooses to use that when they can.

Thank you for posting a summary of you calls today.
 

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Discussion Starter · #13 ·
Latest news. A relative just returned from a trip to Europe. He is a retired chemical engineer from Shell Oil. FWIW his opinion was. If the 5W-20 and 0W-20 were both formulated with essentially the same additive packages the only difference that SHOULD be is the 0W-20 should flow faster at low temperature. At engine operating temperatures and higher (AC on in stopped traffic) both should have identical protective viscosities, that is both be at their rated 20. He went on to say for the 0W-20 to qualify as a 0W rated oil it probably has a better overall additive package because to achieve the 0W would require better base component additives so - unless Ford advised against it (as my Ford dealer used it with a Ford code that isn't the case) then he would say using either would be fine. For "everyday" driving he'd select the 0W-20. Regarding trac, drifting severe duty etc. he said it would depend on boost, average v.s. wot rpm curves and weight towed to select viscosities for those activities all of which would use different viscosities. He said the Ford filter was fine (much better than that orange one) Liked Mobil 1 for the additive package and their filter - just don't extend it as at some point you will be re-cycling contaminants. He said better to use a quality oil/filter and change more often than a super oil/filter and extend the change cycle. If racing he said best you can get and change it after every race. He also liked Kendal oils and Wix filters. He said the Wix engine air filters for Mustang applications were as good or better than the Mtorcraft ones and should be 1/2 the price.
 

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I would ask for proof from Ford that the recommended viscosity has changed. Otherwise, I would insist on what is called for in the manual and on the fill cap, especially if you have any warranty left.
 

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@MT2014 Your comment about a relative returning from Europe triggered this from my memory. I know you are not making a comparison between American and European oils but just for everyone's information even oils of the same viscosity made from the same company can be totally different from each other.

European oils are formulated differently than American oils in some cases. One example is Pennzoil Euro Platinum 0W-40 Full Synthetic vs Pennzoil Ultra Platinum 0W-40 SRT. The SRT oil meets MOPAR spec for use in the 392, but the Euro is not approved for the SRT. Same viscosity. Same company yet one is approved and the other is not.

What additives make the difference between these 2 oils? European oils use different SAPS for emissions requirements. Next time you see your relative maybe they can better explain the differences and what pros and cons there are using one oil in an application it does not meet the spec. Because I certainly can't explain it.
 

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It was my understanding the reason manufacturers recommend "0" vs "5" is because the thinner the oil, the better gas mileage, which helps with Government regulations when selling new vehicles. (please correct me if I'm wrong) I live in Florida where the temps get pretty hot during the summer and my mechanic recommends using 5-20 in my Shelby GT. I use the Amsoil full synthetic Signature Series "25K mileage or 1 year" replacement in all my cars. I never put more than 10K on this car in any year so I only need to change the oil once a year. I have been doing this for many years and have never had any engine failures in any of my vehicles.
 

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Don't worry too much about the "OW" part, it just means it flows better in winter, what you need to pay attention to is the -20 part. Many of the newer engines use the oil AS the bearing for cams and such, to thick and it won't lube well because it can't flow past the tight tolerances as it should.
 

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I know we have discussed oil change intervals and filters but I could not find discussions on viscosity. My manual (which is usually my bible) states I should use Ford Motorcraft 5W -20 engine oil. My Ford dealer said "things have changed since my manual was printed in 2014". I have a 2014 Mustang Convertible (premium and pony packages) with the 3.7 engine. The dealer invoice stated Ford Motorcraft 0W-20 "full synthetic" was used. I asked for an extra quart and they sold me 0W-20 Mobil "full synthetic" and said that is what they are now using. So - did they use Motorcraft "full synthetic" or Mobil "full synthetic" and does it even matter which "brand" they used? My opinion is that Mobil "full synthetic" is lower quality that Mobil 1 which uses higher synthetic base components. There are 43,000 Km on the engine and I have driven 1000 Km since the oil change and there is no sign of oil usage. There are no audible sounds that concern me like clacking tappets etc. Any thoughts appreciated.
I asked the same question as Ford put out something about changing the oil in my 99 Mustang six to that - my question is why would you? This makes no sense to me in an engine that has been running for thousands of miles, NOW you are going to introduce a thinner oil. My ford dealer did it once in an oil change, and my oil consumption went up. Went back to the oil listed on the dipstick of the car, and oil consumption went down again to where it had been before. I got 200,000 miles on my six engine before I almost overheated it due to a burst radiator hose, at which time it started getting oil in the coolant intermittently, particularly around town. So I had the engine rebuilt. The engine rebuilder, ARCE motors in El Cajon Ca, recommended staying with the oil called for, as the engine looked very good when rebuilt, and was running excellent - just too hard to track down that intermittent oil in the coolant.
 

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We will never get a solid answer why service departments are pushing 0W oil into the crankcase where 5W is specified. It probably falls in a similar category electing to use costlier full synthetics when not a requirement. Are people attempting to fix the unbroken?
 
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We will never get a solid answer why service departments are pushing 0W oil into the crankcase where 5W is specified. It probably falls in a similar category electing to use costlier full synthetics when not a requirement. Are people attempting to fix the unbroken?
The old slogan “Ford has a better idea”, still rings in my head. Someone apparently thinks it a better idea, but doesn’t necessarily have data to prove it.
 
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