Mixing Mobil 1 and Pennzoil regular

Messages
11
Location
Missoula, MT
Newbie here, but certainly seems like the place to ask this question. For the last 20,000 miles I have been running a self-mixed Mobil 1 synthetic and Pennzoil regular (both 5W-30). Basically 2 qt synthetic and 1.5 qt regular in my 1993 Nissan Pathfinder. I just had an oil analysis done, with 2100 miles since my last change- the metals were: iron 6 ppm, aluminum <1, chromium 1, copper <1, lead 2, tin <1, nickel <1, silver <1, silicon 6. Only thing that was high was zinc 896, phosphorus 735 and calcium 2006 ppm, but the lab said this stuff was all additives/detergents and not to worry. I worry somewhat that mixing the different oil types might be a problem, but considering the results from the analysis, should I? madkiwi
 

J

Messages
434
Location
Berkeley
quote:
Originally posted by madkiwi: Newbie here, but certainly seems like the place to ask this question. For the last 20,000 miles I have been running a self-mixed Mobil 1 synthetic and Pennzoil regular (both 5W-30). Basically 2 qt synthetic and 1.5 qt regular in my 1993 Nissan Pathfinder. Only thing that was high was zinc 896, phosphorus 735 and calcium 2006 ppm, but the lab said this stuff was all additives/detergents and not to worry. I worry somewhat that mixing the different oil types might be a problem, but considering the results from the analysis, should I? madkiwi
Hi, Yes, Zinc, Phosphorus, etc are additives. As for the mixing ... don't. Mobil 1 10W-30 is more shear stable than Mobil 1 5W-30. It will never get cold enough in San Francisco for you to exploit difference between pour points of Mobil 1 5W and 10W. Mobil 1 10W-30 pours at -40. We never see 0 in the Bay Area, as you know. Just extend your drain interval with straight Mobil 1, if cost is an issue. You will get better protection with straight Mobil 1 than with home brew. Home brewing should be limited to beer. [Big Grin] [Razz] [Cheers!] Jae
 
Messages
3,667
Location
St. Charles County, Missouri
Personally I think that mixing brands and additive clash is no big thing. If you're going to mix Mobil 1 and Pennzoil it's no different than mixing Mobil 1 and Drive Clean and Pennzoil is a better dino. oil. At any rate, this provides more bang for the buck than buying a 10% blend.
 

madkiwi

Thread starter
Messages
11
Location
Missoula, MT
J, I was using the 5W-30 for fuel efficiency. I was under the mistaken assumption that it was more free-flowing than 10W-30, of course I now know that when it's hot it is exactly the same. However, Nissan does recommend 5W-30 for most conditions. But I was wondering if I should go back to stright dino oil? The technician at the lab said I could just go back to regular oil, as my engine is not conditioned to a pure synthetic. I do oil changes at 3500 miles regardless, I just don't like the idea of circulating dirty oil no matter how well the oil itself resists breakdown. Once oil is full of garbage, it should be replaced, right? I posted my tests on the oil analysis forum and one guy though my engine should be toast based on the "additive clash"- until he read the results. I interpreted his tone as confused (or maybe stunned!). He seems to be surprised it isn't worn out. Of course that doesn't make me feel superior or brilliant, just very lucky. I want to do the right thing, not blunder along. madkiwi [ April 11, 2003, 11:08 AM: Message edited by: madkiwi ]
 
Messages
3,667
Location
St. Charles County, Missouri
To repeat something I've said here and on other forums. I've owned more than 25 cars and 3 bikes over the years. Only three could be said to have succumed by any engine related problem. A Corvair (hahaha), a Plymouth Arrow that I overheated (coolant, really), and a Caravan that had crapped out oil seals at 100K (typical Mitsu. 3 liter problem). So really stating that any of these problems were oil related is really pushing it. That's why Quaker State used to give a lifetime engine guarantee--- oil related failures are extremely rare. Unless you had one of those sludged Toyotas, that is.
 
Messages
491
Location
Ottawa
So what you are saying is that all dino oils will leave sludge behind. How can you say that? Even if someone changes out there dino oil at 3k there will be do sludge. My father has a 95 windstar 3.8L and has always done the 3k changes. The engine now has 100k on it and when you look down the oil cap. You can see the head, springs, valves. It looks mint inside, just like someone who was using synthetic oils.
 
Messages
22,187
Location
Colorado Springs
quote:
Originally posted by J:
quote:
Originally posted by madkiwi: But I was wondering if I should go back to stright dino oil? The technician at the lab said I could just go back to regular oil, as my engine is not conditioned to a pure synthetic. I do oil changes at 3500 miles regardless, I just don't like the idea of circulating dirty oil no matter how well the oil itself resists breakdown. Once oil is full of garbage, it should be replaced, right? madkiwi
Hi, If you're dead set on changing at 3,500 oil change interval, premium dino is the way to go. However, your engine will be in better shape if you use Mobil 1 at 5,000 to 7,500 oil change interval. Mobil 1 has a nice package of detergent additives which keeps the crap in suspension. The thing is that dino oil at short oil change interval is a self-fulfilling prophecy. It has more viscosity modifiers which shear more readily than base stock. So, by using dino oil at short intervals, you will get more sludge and not less. [Cheers!] Jae

Um, I disagree with your accertion 100%. Your saying that by using good conventional oil every 3,000 miles, your going to have more sludge/more wear than using mobil 1 every 5,000 miles?
 

J

Messages
434
Location
Berkeley
quote:
Originally posted by Drew99GT: Um, I disagree with your accertion 100%. Your saying that by using good conventional oil every 3,000 miles, your going to have more sludge/more wear than using mobil 1 every 5,000 miles?
Hi, The facts are that dino oil base stock has smaller inherent viscosity index. Therefore, more viscosity modifiers need to be added to cover the spread between low and high numbers. Viscosity modifiers permanently shear more readily than base stock. These are facts, and they're indisputable. [Dummy!] [Razz] [Cheers!] Jae
 

Patman

Staff member
Messages
22,012
Location
Guelph, Ontario
While I don't have any absolute proof, my gut feeling tells me that you'll end up having a cleaner engine if you use a good synthetic changed at 5-6k intervals compared to using a common conventional oil changed every 3k. One of the reasons I say this is because of all the thinning out we see happening in the 3k UOAs on 5w30 dino oil. So as that oil thins out, we know it's VII is breaking down, so it's dirtying up the engine a little bit each time.
 
Messages
6,388
Location
Washington St.
madkiwi How long to you plan on owning this Pathfinder? If only the average time (whatever that is), you'll be fine as said with a conventional oil, and 10W-30 will offer better protection in the latter half of your oil drain interval. If you can measure a difference in fuel mileage, let us know. If you plan on keeping your Pathfinder 'til the wheels fall off, then Mobil 1 10W-30 with 5k oil drain intervals might pay off for you. Ken
 
Messages
509
Location
Las Vegas, NV
Madkiwi, if you want to change the oil every 3,500 mile then use Pennzoil. If you want better protection then use Mobil 1 and change it every 5,000 to 7,000 miles. I believe that you will get better protection for your engine using Mobil 1 even if you were to double the oil change interval and as an added benefit you will spend less time under your vehicle. Please let us know what you decide to do.
 

madkiwi

Thread starter
Messages
11
Location
Missoula, MT
Ken, I love my Pathy. I have had it for 7 years, and at the rate I am driving I won't hit 200K miles for another 13 years. I expect to still own it at that point. Although I have had very little go wrong with it, over the last few years I have lined the cabin with sound dampening and barrier materials, installed a roof-rack, a CB radio, a jerrycan holder on the tire carrier, heavy-duty Rancho shocks, steering damper, idler-arm brace, purchased a full-size rim and tire for my spare, a Borla cat-back exhaust, a hi-flow oiled gauze conical air filter and replaced all the driveline lubes with Red Line (differentials, transfer case, transmission). It is scary to add up the time and money I have put into it. I HAVE to keep it! I am very grateful for all the responses here and in the Oil Analysis forum. Unfortuately it seems like I managed to insert myself into the middle of a religious war- with the opinions on mixing oils polarized on the "NEVER" and "NO PROBLEM" ends of the scale. I am very glad my truck is a perfect example to help prove the naysayers wrong, but that there is a debate at all has made me decide to use Mobil 1 "straight" from my next oil change. Thanks, madkiwi
 

MolaKule

Staff member
Messages
21,950
Location
Iowegia - USA
I think your analysis results were very good for the mix. However, best mixing is done with oils of the same SAE viscosity unless a virgin sample is sent to the lab before introduction to the engine. I would suggest for your future and current mileage a 10W30 such as Mobil 1 (with 8 0z. of Schaeffer's #132 per 5 qts), Amsoil 10W30 ATM (with 4 oz. of #132 per 5 qts), or Schaeffer's 10W30 #703 for extended oil changes. Take a look at the engine clearances in your repair manual. For my Nissan Frontier 4-cyl 2.4L, the clearances are about half the clearances for my Chevy SB V8's. They recommend anything from 5W30 to 10W40, with 5W30 being preferred for lowest Fuel Consumption. I run 10W30 because I want a thicker average hydrodynamic film thickness for all temps. Now maybe when the clearances get higher, say at over 250k miles, I may use 10W40. Using the Laschee equations for various clearances, the equations result in oil viscosities ranging from SAE 10 weights to SAE 40 weights. For me, a narrow-range SAE 30 weight is the best compromise for best overall film thickness, minimum viscosity index improvers, and fuel consumption. Synthetics use the least amount of VII's (or none at all in some cases) because the inherent VI for base fluid is wide and very linear.
 

J

Messages
434
Location
Berkeley
quote:
Originally posted by madkiwi: But I was wondering if I should go back to stright dino oil? The technician at the lab said I could just go back to regular oil, as my engine is not conditioned to a pure synthetic. I do oil changes at 3500 miles regardless, I just don't like the idea of circulating dirty oil no matter how well the oil itself resists breakdown. Once oil is full of garbage, it should be replaced, right? madkiwi
Hi, If you're dead set on changing at 3,500 oil change interval, premium dino is the way to go. However, your engine will be in better shape if you use Mobil 1 at 5,000 to 7,500 oil change interval. Mobil 1 has a nice package of detergent additives which keeps the crap in suspension. The thing is that dino oil at short oil change interval is a self-fulfilling prophecy. It has more viscosity modifiers which shear more readily than base stock. So, by using dino oil at short intervals, you will get more sludge and not less. [Cheers!] Jae
 
Top