Bert

hmmmm . . . this seemed like a good idea at the time but now I am second guessing myself . . .

I was changing my oil and I had on hand Royal Purple 5W-20 and Mobil 1 EP 5W-30. My car calls for 5W-20 but I have been using 5W-30 in the summer because I run the car on the road track a few times each year. I have always used the Mobil 1 EP but lately saw a few posts saying Mobil 1 has gone down hill so that's why I bought the Royal Purple.

It being early spring and still cool, not being sure if I will get to the track or not this year, and wanting the supposedly better additives of the Royal Purple and also some of the higher viscosity of the 5W-30, I used roughly 50/50 mix of the two.

I don't really see how that could be a bad thing, should accomplish what I wanted, but now I'm wondering . . . thoughts?

SilrBult

Let me preface my remarks by say that I am NOT a petro-chemist and even if I were I still don't have access to the sort of testing equipment necessary to provide objective information. I have however built a few engines and have worked on quite a few others as well. Many of these engines have been either performance oriented or actual racing engines. I don't see any problem with mixing oils of different viscosity so long as they are from the same manufacturer and of the same oil type eg. 40w Vavoline racing oil with 50w Vavoline racing oil. In fact Brad- Penn has said exactly this. I do see a problem with mixing oils from different manufactures. There isn't any way short of a chemical analysis to know what the additive packages are from each brand or how they will interact with each other. Discussions regarding the merits of different oils have been going on for a very long time and I don't think it's possible to know without being a petro-chemist with access to all the necessary equipment to determine which oil is best [?]. The reason I use the question mark is that we first have to define what we mean by best. Best at what? High temp protection? Keeping the engine clean? Longevity? Anti-wear protection? For example racing oils are generally better than standard oils in regard to anti -wear properties, high temps and fuel contamination, but often don't have or need as much detergent additive as standard oils. Racing engines don't have to go very long between oil changes. I doubt that you've done any real harm by mixing these two oils, but in the future I would stick to one brand and so long as it has the appropriate API rating you should be fine. In case you're interested I use Mobil 1 5w30 in my '14 GT and Vavoline 5w30 Maxlife synthetic blend in my '01 Mustang 3.8 six cylinder. The '01 has over 400,000 miles on it with over 200,000 miles on the present engine and it runs fine with oil consumption of approx. 1/2 qt. between 4,000 mile changes. Some of that usage come from a little seepage from the rear main seal, not burning. The '14 Gt has just a bit over 63,000 miles and I've been sending oil samples to Blackstone Labs for analysis every other oil change [ 4,500 miles between changes ] for the last 30,000 miles. The lab checks have all come back showing very low metals and plenty of additive left. The only measurable oil the 5.0 uses is a few tablespoons from the catch can.

Bert

thanks for those thoughts; I was also wondering if the additives might be "incompatible" but the Royal Purple says on the label that it is compatible with other oils so I guess I won't worry about it, but yeah I'll probably stick with the Mobil 1 (or another good full synthetic) in the future

David Young

I use Mobil 1 5W30 in my v6 Mustang and my v6 Edge. I use Mobil 1 10W40 in my old 91 F150. Nice to be able to buy it from Walmart, the Motorcraft oil filters also

Bert

Yep I've been buying my Mobil 1 from Walmart for years and all my engines seem to run forever . . . lately I've been using the EP (Extended Performance) because I read it is a true Group IV synthetic or something like that, and it's only a couple dollars more for the 5-quart jug. The regular Mobil 1 is not a Group IV, guess it is Group III though I don't really know what I am talking about ;-). I hear that the Mobil 1 has been cheapened and not as good as it used to be, don't know if that is true, but I guess they were probably talking about the basic Mobil 1 not the EP.

shaneyusa

I am kind a with SlvrBult on this one. Different weights from the same manufacturer usually are not a huge problem for conventional oil. But you are talking synthetic oils here. I would be very careful and avoid mixing in this case. I would suspect that each company likely uses a different recipe to create their synthetics. I am not sure of the process but would be concerned just how well they would mix and work together. I would be very concerned if this is the oil you plan to have in when you hit the track. I would be using a single type of oil, no mixing especially for track use, but I would not do it for even easy driving.

5.M0NSTER

Another vote for keeping it to one manufacturer for track use. For street vehicles I've mixed, but it's street use. It will most likely work to be honest, but if you can, keep it unmixed.

On the track I've had great results with Mobil 1, and fantastic results with Castrol Edge according to Blackstone labs. And if you hit 3-4 track days per year, and do about 8000 miles per year, Blacstone convinced me 1 oil change per year is enough. And my Mustang called for 5W-50.

Actually my first track weekend the car was eating oil. It was at about 4000 miles and still on original factory oil. I remember needing to run out to local car parts store and I got Mobil 1 15-W50 as they didn't have anything in 5W-50. So for 2 track days I did run a combination of Ford 5W-50 and one quart of Mobil 1 15W-50. I changed it a few weeks after and ran 15-50 from same manufacturer ever since.

Bert

Thanks for the thoughts guys. I still feel like it's probably fine but I have enough doubt that I'll probably change it again before any track day this year, if the tracks even open up, even though it won't really be "needed" due to mileage between now and then.

5., were you using the Mobil 1 EP ; and what was better about the Castrol Edge? Do I understand correctly that you'd recommend the Castol Edge over the Mobil 1? (amazingly enough that's what the guy at the local Advance Auto recommended also)

EDIT: when all else fails, read the instructions! RP label says it is fully compatible with other synthetic oils . . . so I guess I won't worry about it too much right now, but probably will change it anyway before hitting the track and probably will use Castrol Edge

5.M0NSTER

Hey Bert, long time man!

I used Mobil 1 racing in 15W-50. I don't think it's an EP oil, but I could be wrong. I used it to top off that first time, and then 1 season with 3 track days. I did not have oil analysis done with it, so I can't saw which was better.

Than I switched to Castrol Edge (Syntec) in 5W-50 when one of my local Advanced Auto Parts started carrying it consistently, so I didn't have to worry abut flow in cold weather (5W instead of 15W). I would drive my car till November in Michigan, which means sub freezing temps on many mornings. Last oil analysis I had done with it was after 11 months in the car, with 3 track days on it, about to do a 4th. Over 7000 miles on the oil, and it sat in the oil pan over the winter (I changed it once a year in October typically, so I changed in in October, and had analysis done following September). Analysis showed the viscosity was on spec, flash point was on spec and additive package still had more than 50% life in it. Blackstone recommended trying analysis again after a longer drain interval. I was really impressed. Car felt happy with it too, no tick. With Motorcraft it would tick sometimes. So I can back up my recommendation of Castrol with data, Mobil 1 also felt good, but I have no data.

I think you're probably fine as well, no need to replace good oil just to do a track day. I would consider topping off with 5W-30 though or ticker. 20 weight oil can get too thin at high load and temps, causing low oil pressure.

David Young

Several years ago while reading about finding the best motor oil to use, I noticed in all the test 5W30 was used. They said 5W30 would thin down to 5W20 under hot engine conditions. I have never found what 5W20 thins down to under hot engine conditions . This is why I use 5W30 weight oil

Bert

interesting . . . that kinda contradicts the meaning of the grade number as I understood it . . . I thought the 5 means it acts like a 5 weight when cold, and the 30 means it acts like a 30 when hot . . . ????

David Young

You're right. The 30 weight thinned down to 20 weight when 'extremely' hot. Maybe a 90 plus degree day and running it hard. Maybe like track conditions.

SilrBult

There has been a lot of confusion over the years as to just what the viscosity numbers mean. I may not have this exactly right, but my understanding goes like this, A 5w30 oil will have a cold flow rate equivalent to a 5 weight oil. This dosen't necessarily mean it's as thin or thick as a 5 weight, only that it flows like one cold. Likewise the 30 part of the rating means it offers protection equivalent to a 30 weight oil when hot, not that it is necessarily the same thickness as a 30 weight. To the best of my knowledge all oils thicken when cold and thin down when hot.

Bert

yeah, that is the confusing part . . . apparently there must be some standard oil that is used for comparison for "flows like a 5 weight standard oil when it is cold" and "flows like a 30 weight standard oil when it is hot" and I believe it is all about viscosity, technically not how well it protects (though protection is related to viscosity)

5.M0NSTER

I think all you guys are correct. And the oil viscosity is measured at standardized temps. 0 C for cold, and 90 C for hot. The issues is that during a track days oil temps are closer to 140 C.

Bert

thanks 5., makes sense, and good to chat with you again -- hope all is well over there in Germany, I hear they are starting to open up gradually over the coming weeks; we have a similar plan here, but right now it sucks, all the tracks are closed until further notice!

5.M0NSTER

Thanks bud. Yeah, all is "new" well. Some small and medium size stores are opening, and 4th, 8th and 12th grades are going back. Just the graduating classes though. Everything else is still shut down, and I don't think it will open soon.

Same here with track days. I was supposed to have my first event for the year at Nurburgring Nordschleife next week, but it is of course canceled.

Hope you're staying healthy and hanging in there my friend.

14Mustang_Driver

i just had the oil changed in my car and with it being parked for long periods i was told to stay away from royal purple (always used that in my mustangs) but was told that i should put AMSOIL 5w20 synthetic in my car so i got them to put that in, i reset the the oil life in the car and i drove it for about 400km or approx 250 miles and when i flipped through the gauges i noticed that it was at 55% oil life not sure why the oil broke down so fast but next time i won't use AMSOIL unless i did something wrong

Mustang Freak

I highly doubt the Amsoil broke down in 250 miles of driving. I used to use Amsoil and only changed it once a year and I averaged about 10k a year. Maybe the oil reset button was never set back to 100% oil life.

Bert

My understanding is that the oil life meter does NOT measure the actual condition of the oil; rather it tracks miles traveled, passage of time, and other factors like the duration of drives that affect the oil life. I think it is mostly based on miles and elapsed time. So if you did actually reset the oil life correctly, then my guess would be that several months have passed? I have noticed with my 2010 that is says "oil change required" after 6 months, regardless of miles driven.