partisan

My 2002 ZO6 is about ready for an oil change. I was planning on going with the Mobil1, but the BEST automotive repair,maintenance shop in our area uses Royal Purple.
Do any of you know anything about Royal Purple Syn oil???? Thanks!

bracketshark

I used RP in my car last oil change, I see no difference from the Mobile full synthetic. I'm going back next oil change. I don't beat on my car though.

vettenuts

Every used oil analysis I have seen indicates RP isn't very good oil when compared to other oils. Based on that the cost doesn't seem warranted. Personally, I don't and wouldn't use it.

Cheesecake 07

+1000

mojo1

I put it in my new truck the first oil change, I dont like it , seems the motor is noisier, going back to Mobil 1 next change.Got my vette back on the road so it might take a while before the truck needs new oil.

zdeckich

I have used it in my 04 GTO and 06 Mustang GT with zero problems.

Russ K

Royal Purple has their HPS oil that has more ZDP & high pressure additives than their high performance oil (that is just another new car approved oil)

Russ Kemp

85corvettec4

i just bought amsoil for motor tranny and diff cost me about $140 hopefully i enjoy it

baxsom

Don't speculate. Use it until the oil life indicator says its time for a change or one year like the manual says and then send in a sample for a used oil analysis. Go from there.

reath1

Used Mobil 1 since I bought the car. Never a drop low between changes. Used RP last oil change and I am 1 qt. low at 2800 miles. Going back to Mobil 1.

leadfoot4

FWIW.....there has been a bit of discussion here, about the EPA's latest requirements of lower ZDPP content in motor oils. Therefore, the "regular" Mobil1 that we buy today, is NOT the same formulation of Mobil1 that GM specified for our cars initially.

However, Mobil1 "high mileage" oil has the higher levels of ZDPP, and is available in both 5W-30 and 10-30 weights. This oil meets the older "SL" specs, compared to the "SN" specs that the regular Mobil1 meets.

85corvettec4

but im a guy who doesnt like swellers till the 90k/100k mark

C5Natie

Royal Purple is not much better if at all them Mobil 1. However for the best advice on oil go to www.bobistheoilguy.com. Here on this forum most will be pro Mobil 1 because there's a sticker on their car that says to use it. There are a few better "off the shelf" oils out there. Pennzoil Ultra is one that comes to mind or Rotella and VR1 racing synthetic for modded engines. In my experience, for performance driving, you can do better then Mobil 1. It's a good oil and I use it my daily drivers sometimes so don't get me wrong. Also if you don't mind spending a little more on a boutique oil then Redline followed by Amsoil are top notch.

leadfoot4

What "swellers" are you referring to??

Pumba

First, let me start out by stating that I do not use either Royal Purple or Mobil 1 synthetic oil in my Z06. So, I do not have an axe to grind.

Second, let me state that I am an OEM Powertrain and Chassis engineer. So, I have a professional background in engines and lubricants from many years of engine dynamometer and vehicle testing.

If you are still using 5W30 oil in your LS6 engine you should stop. Whether you choose Mobil 1, Royal Purple, AMSOIL, or Red Line, you should switch to a 0W40 or a 5W40 grade. These grades better protect your engine at both cold temperatures and at high temperatures.

Next, if you want to see a comparison between Mobil 1 and Royal Purple go to this web site - http://www.royalpurpleconsumer.com/p...hps-motor-oil/

Good luck with your decision.
-

85corvettec4

seal swellers in high milage

strand rider

I have seen this statement before and it seems to imply that the oil formulations of the past are better than the formulations of today. I question this assumption, but without any special expertise.

The anti wear agents are now different, but are not known to be inferior, in use, to me. I can only assume The engineers working to certify modern oils know what is progress and what chemicals to avoid. I assume the wear agents now used are up to the task and help the cats to last longer than older formulations. Since I have cats on the car, preserving them is a plus for me. I assume the modern engines are asking more of the oil circulation, so it is hard to accept that modern oils will be a lesser choice .

Another important issue is that the oil is used for cooling. It is well know the LS design was not possible without the cooling effects of syn oil.
Cooling is considered with the GM spec test. Any lubricant without the GM Dextros label has unknown cooling properties with these engines, and all oils cool differently . The new (LT) engines even use oil for cushioning, as the valve train is submerged.

I am just a guy who reads a lot of stuff here, and that is pretty much all I know about the situation. Don't think I am an expert or posting to play gotcha with the good poster I quoted. His info might be better than mine., but does not address actual use, just compares specs for one additive.

I question this approach, in that if you choose to run lubricants that are outside of the approved specs for the application, you might get wear performance that is also outside the specifications . The good poster's statement do not address oil cooling. Without this consideration, I would not act on this advice. Might be perfect advice, I just require more information to support the position.

I want my engine to go as long as possible, and my skill level isn't high enough to go messing with oil specifications. Trying to end run a guy who works with oil for a living is going to be pretty tough in my book, oil chemistry seems very complicated. Doesn't seem to slow anybody down from doing what they think is better. I plan on keeping my car, so will live with the results of my decisions. Others will sell, and never know if engine life was compromised.

One guy with an LS1 corvette posted he still uses conventional oil with conventional change intervals, and all is fine. I am sure it is fine , for his needs. A skilled engineer might have other priorities.

The GM Dextros label is an attempt to make it easy to select corvette oil. Dextros 5 30 is the spec, any oil without the label is suspect, and might not work as well . Since I really don't care what oil I use, beyond correct selection, I just get the stuff with the Dextros label.

Mobil 1 has an 800 help line if you really get stuck. I called about a turntable bearing and now run 5 -30 mobil 1 there also. Sounds great.

In my reading the Ls engines don't have the old wear issues that extended milage oils are engineered towards.

leadfoot4

FWIW, I put some 0W-40 Castrol Edge in my car just before I put it away for the winter. I like to start the car 2-3 times during the winter, just to circulate the oil, wet the seals, etc, and thought the "0" would circulate quicker in the colder temps. I put the oil in, fired up the engine to take the car for one last ride, and the engine was "noisier"....like more lifter clatter. I was dumbfounded.

As much as I hated to do it, I dumped $50 worth of oil, and refilled the car with Pennzoil Ultra, an oil I had used a couple of years ago, when I got 6 quarts of it for free, and was impressed on how it seemed to quiet the engine's "sewing machine" sound. And yes, after dumping the 0W-40, and refilling with 5W-30, the engine returned to it's normally quiet state....

LSOHOLIC

IMO.......application specific.

~ stock daily diver
~ road racer
~ drag racer
~ 1.3 per cube to 2.2 per cube
~ n/a, blower or turbo
~ etc...........

But, there are several great SAE papers on this.........as well as "other" independent testing.

C66 Racing

Many will take this test with skepticism as it was commissioned by AMSOIL, but even if you ignore how the AMSOIL performed and only look at Royal Purple vs. all the rest, I think you'll find that Royal Purple is a middle of the pack current spec oil:

AMSOIL Performance Test: A Study of SAE 5w30 Synthetic Motor Oil

There are really two issues that impact this - basestock and additives.

Oil's are all different. There is no definition in the U.S. on what "synthetic" means. The API only defines them by Groups.

Group I base oils are the least refined of all of the groups. They are usually a mix of different hydrocarbon chains with little or no uniformity. While some automotive oils use these stocks, they are generally used in less demanding applications.

Group II base oils are common in mineral based motor oils. They have fair to good performance in the areas of volatility, oxidation stability, wear prevention and flash/fire points. They have only fair performance in areas such as pour point and cold crank viscosity. Group II base stocks are what the majority of engine oils are made from. 3000 mile oil changes are the norm.

Group III base oils are subjected to the highest level of refining of all the mineral oil stocks. Although not chemically engineered, they offer improved performance in a wide range of areas as well as good molecular uniformity and stability. By definition they are considered a synthesized material in the U.S. and can be used in the production of synthetic and semi-synthetic lubricants. Group III is used in the vast majority of full synthetics or synthetic blends. They are superior to group I and II oils but still have limitations. Some formulations are designed for extended oil changes. Almost all off the shelf synthetics today are Group III.

Group IV are polyalphaolefins (PAO) which are a chemically engineered synthesized basestocks. PAOs offer excellent stability, molecular uniformity and performance over a wide range of lubricating properties. PAO is a much more expensive basestock than the highly refined petroleum oil basestock of Group III.

Group V base oils are also chemically engineered stocks that do not fall into any of the categories previously mentioned. Typical examples of group V stocks are Esters, polyglycols and silicone. Red Line uses an ester basestock.

In the 90s, Mobil filed suit against Castrol for falsely advertising Syntec oil as synthetic, when in fact it contained a Group III, highly hydroprocessed mineral (Dino) oil, instead of a chemically synthesized (Group IV or V) basestock. Due to the amount that the mineral oil had been chemically changed, the NAD decided in Castrol's favor. As a result, any oil containing this highly hydroprocessed mineral (Dino) oil (currently called Group III basestock by the American Petroleum Institute) can be marketed as a synthetic oil. Since the Group IV and V synthetic basestocks (polyalphaolefin or PAO, or polyol esters) are much more expensive than the Group III basestock, most of the oil blenders switched to the Group III basestock, which significantly increased their profit margins.

Through this change and into about 2007 or so, Mobil 1 staunchly kept to a Group IV PAO basestock when almost everyone else had gone to Group III (expect a few small companies like AMSOIL, Red Line). About 2007, that changed and Mobil 1 almost certainly followed to Group III. Their website today now states "... including... PAO...". Who knows what that really means.

Note that Group III, IV and V can be, and are, blended for good reasons. Adding polyol esters (Group V) in small percentages to PAO (Group IV) both lowers the coefficient of friction.

In addition to basestocks, the other main difference in oil's today is additives, and in cases of extreme usage like the track, the anti-wear additives.

Phosphorus, along with zinc, in a compound called ZDDP, or or zinc dialkyl dithio phosphate, forms an oil's primary anti-wear additive. Unfortunately, phosphorus slowly poisons the cats and prevents the catalytic exchange that allows them to function properly. To ensure auto companies could meet the EPA's 100k+ emissions requirements, the API has slowly been dropping the limit on phosphorus.

During the C4 model years, most good oils had around 1200 ppm phosphorus/zinc. When I bought my 02 Z06 in 2001, most good oils still had around 1200 ppm phosphorus/zinc.

From 94-97, the API SH spec allowed up to 1200 ppm phosphorus for 5w30 and 10w30 and didn't address other 30 grade viscosity like 0w30. In 97, API SJ dropped the limit to 1000 ppm, but still did not address 0w30. In 01, API SL kept 1000 ppm phosphorus, but added 0w30 to the spec. In 04, API SM further dropped the limit to 800 ppm, but for the first time set a floor at 600 ppm and advertised that oil's were better. Essentially they were capping how much phosphorus the better oils could have and mandating the lowest amount the cheapest oils must have. The current API SN spec still has the band 600-800 ppm phosphorus. Dexos1 is similar.

So, any oil labeled to meet the current API SN/dexos1 spec will be limited to 800 ppm max phosphorus. This impacts how well it will be able to perform in anti-wear, such as might be seen in your bearings under heavy load.

To see how this all impacts oil performance, consider the High Temp High Shear (HTHS) viscosity of these oils. The HTHS viscosity is a measure of the oil's viscosity at 300F under heavy shear, as might be seen in your bearings, particularly at the track.

Mobil 1 10w30 - 3.0
Mobil 1 5w30 - 3.1
AMSOIL Sig Series 5w30 - 3.2
AMSOIL Sig Series 10w30 - 3.2
----------------------------------------------
Mobil 1 High Mileage 5w30: 3.3
Mobil 1 High Mileage 10w30 - 3.5
AMSOIL ZROD 10w30 - 3.6

The top four comply with API SN limit of 800 ppm phosphorus. The Mobil 1 High Mileage 5w30 and 10w30 have 1000 ppm phosphorus, 1100 ppm zinc. The AMSOIL ZROD 10w30 has 1320 ppm phosphorus and 1440 ppm zinc.

You can draw your own conclusions from these values, but I've been watching the HTHS drop over the years. Back when I started racing, AMSOIL's best street oils had HTHS of 3.6 - now they are down to 3.2 and to get back to 3.6 I've gone to oils like the ZROD (I now use AMSOIL's Dominator Racing 10w30 which is also 3.6). My opinion is that both the basestock and the additives have lowered the performance of the best oil's over the last decade or so. Does it matter on the street - probably not. For that track, I would never take my car onto the track without a high ZDDP oil. And if I were a Mobil 1 user, I'd be using the High Mileage oils vice the base Mobil 1 or Extended Performance Mobil 1.