I posted this somewhere else but wanted to make it more noticable and end the stupid assumptions:

http://www.synthetic-motor-oil-air-filters...ommendation.htm

I kind of figured this. And people claiming it will void your warranty can go fly a kite.

 

I'm not much for flying kites, so I'm going to have to go with Amsoil on this.

Amsoil was the first in synthetics, and I trust their product and knowledge. I've been using Amsoil for years, and have about 3 cases in the garage and three more on order, running it in two cars and three race bikes. It's good stuff.

 

Interesting . . . but before you squash any more "rumors" maybe you should read page 2 of your warranty guide.

The Boss Hog

 

Car companies have been saying use only their parts and oils that meet their requirements for years.

 

"Boss"

I have agreed with you on much of what you have to say. But, screw what the warranty guide says. When people are re-tuning computers, putting on CAI's, new exhaust, headers, etc. and others are "sure" that it won't void their warranty it just seems silly to worry about oil weight.

Warranties seem to always try and catch people with their pants down, and this one obviously has you by the *****.

 

Oil weights can have a much higher effect on engine life than all the parts you mention, since they are not INSIDE the motor.

Oil weight effects a LOT of engine parameters such as drag on the crank & pistons, oil pressure, heat generated in the cylinders, wear on the oil pump gears, and a host of other factors. If the motor is designed for a "thin" oil like 5w20 and you use 5w30 in it, it CAN have effects on the motor.

Your unlikely to ever be denied a warranty claim for using the wrong oil. That's NOT the same as saying it won't have any detrimental effects on your engine.

 

The owner's manual clearly states "to protect your warranty, use 5W20....". I'm sure the detrimental effects you mention are the reason why it says that. Personally, I see no logical reason NOT to use 5W20.

 

If you can't find it when doing your daily shopping (say in synthetic), I can't see why 5w-30 isn't a suitable substitute.

We've already discussed this ad nausea, and apparently I'm wrong.

 

I will agree that if it's time to change the oil and you can't find 5W20, 5W30 is a viable substitute but I wouldn't switch over 5W30. I'd go back to 5W20 on the next oil change.

 

You're probably right. Truce. I read over all of the posts and realized it's a pretty dumb argument (on my behalf). I'm sure you took offense to some of what I said and I appologize for that.

I just see way too much of people claiming they know what they're talking about and too often being proven wrong with a little research.

 

Fair enough.

 

Didn't I hear something about the variable valve timing being activated by the oil system pressure? Wonder what changes slightly more viscous oil (5W-30) would make to it's valve timing curve?

Also note that the oil Specifications in the 2005 Mustang Owners Guide says:

Use SAE 5W-20 engine oil.
Only use oils “Certified For Gasoline Engines� by the American
Petroleum Institute (API). An oil with this trademark symbol conforms
to the current engine and emission system protection standards and fuel
economy requirements of the International Lubricant Standardization and
Approval Committee (ISLAC), comprised of U.S. and Japanese
automobile manufacturers.
To protect your engine’s warranty use Motorcraft SAE 5W-20 or an
equivalent 5W-20 oil meeting Ford specification WSS-M2C930-A.


They're not requireing that you use only Motorcraft oil...just ones that meet these specs. Mobil 1 5W-20 and Castrol Syntec 5W-20 meet both of these specs. Don't know about the Amsoil myself...anybody out there got a bottle to check?

 

In a related topic, the 5.7L Hemi in the 300C/Magnum is spec'd to use 5W20 and if you use anything else, the Multi-Displacement System won't work. Apparantely thicker oil prevents it from working properly. The variable cam timing on the '05 Stang could work in a similar manner.

BTW, the Hemi engines that don't have MDS are spec'd for 5W30.

 

I am a true Ford guy right down to the oil and filter on all my cars motorcraft 5w-20 (or whatever it says to use) and a motorcraft filter every 2500mi on all my cars and I have never had a problem. Why try to fix something that isn't broken.

 

How about a new prespective on this issue. I am a mechanical engineer and know a little bit about oils and how they protect moving parts.

First, the main twist of the story seem to be that Ford, GM , Crystler, etc... are telling people to run a tinner oil to meet Cafe standards and it will some how harm or shorten the life of your engine....

Here is my twist. What if these guys have been lying to you all along and the tinner oils actually improve the life of the engine and they have told you stories for years to shorted the life cycle of thier products and get more revenue...

Ok, this sounds silly does it not? However, does it sound any more silly that the first argument?

Thicker oils do not necessaraly protect your engine any better than a thin oil. Here is why. Oil's primary function is of course lubrication, but it also is used to cool the engine in certian places. A tinner oil can flow better than a thicker oil so it can remove more heat.

Also, it is obvious that at some point a thicker oil would simply not get into every nook and crany of the moving parts. Think about how poorly a thick ( say 90 weight ) gear oil would flow in your engine. It would have high oil pressure but very poor flow. I doubt it would even reach every part of the engine.

I personally doubt that you could measure the wear difference between 5w20 and 5w30 over the life of an engine. There simply is not that much difference between the two oils.

In the old days, oil was selected by season due to how it flowed or thinned out due to temperature. The modern oils ( with polymer addatives ) do not really have this problem.

Finally a tinner oil does produce more hp and that is ofcouse the point of this section of the fourm....

 

What I mean, is that it is unlikely the dealer will ever run your oil through a centrifuge to determine the weight. Maybe if you grenade a motor, Ford would want to know EXACTLY what happened. But for lesser engine damage, they probably would not bother to test the weight of the oil. If they found out you used the "wrong" oil (like if you TOLD them), they'd almost certainly deny your claim.

 

Grenading the motor was what I had in mind. You're correct, they aren't going to bother with lesser engine damage. But in the event of a catastrophic failure where the engine would be replaced not repaired, I would think a post-mortem would include an oil analysis.

 

After racing motorcycles for years, I have noticed a trend. If you you use thinner weight oil, you will gain a few horsepower, but at the risk of short engine life. I've had 4 motorcycle engines rebuilt, so I have a little experience in this area. Then again, apples to oranges, and the motorcycle engine is spinning aroun 14000 rpm instead fo 6, but still, just stating my experience. I've had motors running fine with thicker oil, then go to something thinner for a few more ponies and had it grenade not too much later. So I'm not sure I'd believe a "thinner oil protects the engine better" theory. Just speaking from experience, not trying to sway people one way or another. But it makes sense that a thicker oil will have a thicker layer of protection over the piece of metal, perhaps causing less engine wear over time. The main part that failed on all 4 motors, was the rod bearing, a very tight metal on metal contact point.

That being said, I don't think there's a big enough difference between 5-20 and 5-30 to cause alarm, and if Amsoil claims there 0-30 will protect even better than 5-20, I'm inclined to believe them. I'm sure they've done more testing on motors and oil than I have, maybe even more than Ford, but can't say for sure.