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Alright, so I bet there are other threads on this same topic, but I'm too computer illiterate to search for them so I'm starting my own. I recently took my car in to get the ford racing hot rod cams put in at a mustang specific shop in Tampa. The guy did an amazing job and I only love the car more. When he gave me my car back he told me that when I had brought it in it was a quart low, and said that I should be sure to be using partially synthetic oil, instead of full synthetic oil, for my 4.6 V8. He then gave me a reason that I believe was that there is something in the motor that is paper thin and will let the synthetic oil through. Sorry I can't more specific there, I was too excited to get in my car to take in all that he said. Now here's where things get tricky. I bought my 09 Mustang in May 2014 with 54,000 on the clock. I bought if from a Ford dealer and had extensive service records to show that it had been maintained. Soon after buying it, and ever since then, I put Royal purple full synthetic 5w-20 in it. The car now has 93,000 miles on it, and runs great still. I now have 2 questions:

1.) Should I take the mechanics advice and switch the car back to synthetic blend oil versus royal purple full synthetic?

2.) If I should change it back to synthetic blend versus fully synthetic, should I use a thicker oil such as 5w-30 or 10w-30 since the miles are getting up there? Or would that not benefit the motor?

Oh and just in case this is relevant, I put quite a few miles on my car each year. It is my daily driver to work, that is only about 8 miles away in average start and stop in town driving. I also often do a lot of interstate driving to visit family on weekends, particularly from Tampa to Atlanta and back, which typically puts about 1,100 miles on the car over a course of 4 days.

Thanks in advance for the help!
 

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Theres nothing wrong with synthetic motor oil, its about preference.

And 10w-20 is too thick for our motors. Oil needs to get to the vct solenoids quickly so running a thicker weight oil will not work. You'd have to warm up the oil before you can drive or you risk running the motor with little to no oil in the heads.
 

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I bought my 09 Mustang in May 2014 with 54,000 on the clock. I bought if from a Ford dealer and had extensive service records to show that it had been maintained. Soon after buying it, and ever since then, I put Royal purple full synthetic 5w-20 in it. The car now has 93,000 miles on it, and runs great still. I now have 2 questions:

1.) Should I take the mechanics advice and switch the car back to synthetic blend oil versus royal purple full synthetic? You've been running Royal Purple full synthetic for the last 39k miles without any issue so there's no need to switch back.

2.) If I should change it back to synthetic blend versus fully synthetic, should I use a thicker oil such as 5w-30 or 10w-30 since the miles are getting up there? Or would that not benefit the motor? No. Stick to the recommended 5W-20 viscosity recommended by Ford for proper operation of the VCT.
:smile2:
 

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Engine oil could be a science topic all to itself. There's a **** ton of variables at play. I've used AMSOIL Dominator and Signature 5w-20 with good results. Smooth operation and excellent oil analysis at 10,000 hard driven miles on the signature series. As far as oil weight goes, don't confuse the "w" on the label to mean weight. The numbers 5w-20, 10w-30, 20w-50, etc... is a grade, not a weight. It's related to weight in that it's a grade of the oil's viscosity. However, the spec gravity doesn't really change all that much. An engine with 200*F oil temps and 10w-30 oil will have similar viscosity as an engine with 160*F oil temps and 5w-20 oil. It's very possible for a "heavier" weight oil to actually be thinner than a "lighter" weight oil. Have a look at 5w-30 vs 10w-20. When cold (which is defined as 100*F per oil standards), the "heavier" 30w oil is actually thinner and "lighter" than the 20w oil. The second number is a determination of the oil's viscosity at cleansing temp which is 212*F.

As you get hotter and hotter, the oil gets thinner. This isn't a bad thing depending on how the engine is built. Many newer engines are built with tighter tolerances thus needing thinner oil. More so than that, modern engines have lighter and shorter pistons and piston skirts which calls for narrower ring packages and tighter ring clearances and gaps. You need a thinner oil to ensure the rings still get proper lubrication vs being wiped off the cylinder walls. Does this mean you absolutely have to run 5w-20 and no thicker? No. The modular engine runs just fine on 10w-30. The clearances are more than adequate to accommodate 30w oil. Many parts of the world use 10w-30 off the dealership floor in mod engines. The only reason (as stated by Ford) that the mod motor comes with 5w-20 in the US is for emissions purposes. That said, switching to 10w-30 isn't going to really help with anything either. The only time it would be beneficial would be if you were road racing and regularly seeing 260-300*F oil temps. Even then, many high quality 5w-20 oils such as AMSOIL Dominator, Valvoline VR1, and Joe Gibbs race oil will be up for the task.
 

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If your engine oil ever gets that hot, you should really be thinking about installing an oil cooler.
Depends on what oil you're using. I'd be concerned with conventional oil over ~260*F. Synthetic though, I'd have no problem running it at 300*F, especially if it's formulated with high ZDDP and phosphorus and other racing blends like AMSOIL Dominator and Z-Rod, Valvoline VR1, Joe Gibbs, etc... Engine oil has a very long chain length of 36 carbon atoms which makes it have a very high boiling point. I forget the exact number but it's 550+*F before you reach the boiling point of oil. The difference in viscosity between 250*F and 300*F isn't very much. The oil is hot and happy, I'd run with it. I know a lot of guys that do. I didn't run an oil cooler on my turbo Focus and regularly saw 280-300*F oil temps when racing. I had no issues with it. Cruising down the highway, I'd see 210-225*F and spirited driving would net around 240-260*F. Now I will say that I'd consider 300*F to be about my upper happy limit. If it started tettering toward 320*F or higher, I'd be obliged to look into a cooler.

Hot oil is clean oil is happy oil.
 

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I have a 2006 GT with almost 150K on it and it has had 5W20 full synthetic all it's life (I ordered it new). I am now using Pennzoil Platinum Ultra and the car runs like a new one. Never have to add oil between 5K oil/filter changes. I say pick your favorite full synthetic and go with it. :)
 
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