IMO, manufacturers continue to do research and try to break into the market by making the greatest product ever at competitive prices....that's what every great business does. I think just because a certain oil has worked for 10+ years doesn't necessarily mean you shouldn't try a product that many have reported to take care of your engine even more because of new research, developments, etc.
Just google to see what users are posting:
http://lmgtfy.com/?q=mobil+1+extended+versus+pennzoil+ultra
But you also have to keep in mind that Pennzoil Ultra fully synthetic is a brand new product in comparison. So you'll find a lot more content on Mobil 1 extended, but the recent posts of Ultra is hard to overlook and so is the price in comparison. Penzzoil Ultra is doing so great that there are links comparing it to amsoil high end oils, royal purple, etc, which have by many been considered a different class in itself compared to mobil 1 products that are stocked by almost every mechanic. A few links are below or you can just google by clicking above link...
http://www.automotiverhythms.com/au...a-synthetic-motor-oil-high-quality-blood.html
http://www.tsxclub.com/forums/1st-gen-car-care/61660-results-mobil-1-ep-v-pennzoil-ultra.html
When I did the oil analysis, I was ridiculously surprised how much dirt the Ultra flushed out of my engine in just the first change. Granted I was just using a Mobil 1 extended filter with non mobil oil, but it was only after 3k miles! The ultra has a hyper cleansing additive that keeps the engine cleaner than any other oil according to Pennzoil's tests including Mobil 1 synthetics.
Below is from one of our active members toy4fx:
https://www.infinitiscene.com/search/1/?q=14878-The-Random-Question-Thread?p=248875#post248875
SPECIFICATIONS & APPROVALS
Ferrari – Exclusive to Pennzoil Ultra™ in the USA
Porsche A40
MB 229.5 and MB 229.3
VW 502 00 and VW 505 00
VW/Audi 503 01
Fiat 9.5535 Z2
BMW LL-01
Chrysler MS-10725
Exceeds the requirements of ACEA A3/B3/B4
Exceeds the requirements of API SM/CF and previous categories
Mobil 1 New Life 0W-40 has the following approvals:
MB-Approval 229.3
MB-Approval 229.5
OPEL Long Life Service Fill GM-LL-A-025
OPEL Diesel Service Fill GM-LL-B-025
BMW LONGLIFE OIL 01
VW 502 00
VW 505 00
PORSCHE A40
BMW comes stock with Mobil 1, but Ferrari's comes stock with Penzzoil Ultra.
So I ask, what is oil supposed to do for an engine?
1. Keep it cool.
2. Lubricate it.
3. Grab dirt to flush out dirt through oil changes. Not doing so would cause abrasions, unnecessary engine wear, etc.
Superior oils will usually have dispersants, detergents, anti-wear agents, antioxidants, friction modifiers, anti-foam additives, viscosity improvers, pour point depressants and rust and corrosion inhibitors, which are all found in Ultra Synthetic. Together, they form a formidable barrier against engine wear and sludge formation, and can actually improve fuel economy through reduced internal friction.
I think mobil 1 synthetic and Penzzoil ultra do #1 and #2 both equally well and for a very long time (more than standards). #3, I strongly feel Ultra is superior. This is why I choose Ultra and the fact that it's a lot cheaper compared to mobil 1 extended at wallmart since you are not paying for all that marketing buzz or brand price tag premium.
But either way you will be fine since you are using superior products.