Mobil 1 tends to run thin.

Subaru recommends 5w-30 due to a balance to get better gas mileage and still decent protection for the motor.

Subaru of Japan has the "sports motor oil" rated at 5w-40, and their "racing motor oil" at 10w-60. Take what you will from it, but this makes me believe (because the U.S. is so gas mileage conscious) that the 5w-30 rating is too thin, add the fact that Mobil 1 runs on the thin side of a 5w-30, this can lead to excess burn off. Subaru motors are not the same across the board, we've all seen stock motors having a pretty big difference in whp numbers from the same dynos, just because Mobil 1 doesn't burn off on your car doesn't mean that someone who is burning oil has something wrong with their motor.

As for 15w-50 Mobil 1, that's a pretty thick oil. Due to the fact that it's a lot thicker than the 5w-30, you shouldn't run into the burn off problems. If you don't mind me asking, why are you running 15w-50 on a daily driver?

There are many Subaru motors, all over i-club and Nabisco, that burn off Mobil 1, but don't burn a drop of German Castrol, Rotella-T, or many other oils. Does this mean all these motors are doomed (other than the fact we probably all beat our motors to death)? Probably not.

 

All Mobil 1 bashing aside, and no offense to the OP, but this sounds like the oil change is to blame here. Sure, the dipstick can read full after filling up the sump, but did the engine get run for a minute afterward to circulate the new oil? One quart over 600 miles is ULTRA excessive, and barring a borked engine or turbo I'd bargain that insufficient oil was put in during the change.

 

I'm on my cell phone so my reply will be very short. But a weight rating for a oil is a weight rating for a oil. Saying that Mobil 1 is thinner than any other oil is complete speculation, without any proof I'm gonna take your oppinion as just that. I don't care what oil you run and what the circumstances are, if your burning oil you need to look at your motor. And as far as running 15w50 in my DD, why wouldn't you run it? I'm not trying to make 2 more whp from running a lower weight and I'm not trying to shatter any mpg records (I get in the mid to low teens). I've seen my buddy spin a bearing from using standard 5w30 syn at a track day and multiple knowlegable people said a heavier oil would have helped the problem. Even as stated above the subaru oem oil is 5w30 and the race oil is 10w60, so if you are driving a street car like a race car prepare it as so. I talked to Mike at GST when I had my car tuned on the last motor and told him I was using M1 15w50 and he said that's what they use in their race car, so I'm sold.

 

Would you consider analyses done by Blackstone Laboratories as proof?
Same vehicle, same motor, the Castrol has over 1K more usage and the wear characteristics of the Mobil 1 shows more wear in the chemical breakdown analysis than the Castrol Syntec German-made 0-w30 oil. I would assume that they have enough expertise to know what they're talking about.


Mobil 1


Castrol Syntec

 

I have researched oil on bobistheoillguy.com and there are UOA's that show M1 5w30 shearing down to a 20w in turbo subies.

edit - looks like Roo beat me to the punch

 

+1234

I run 0w30 Castrol, and runs like a champ!

 

Definitely, weight rating of oils is just weight rating. Similar to tire ratings, it's all different by brands. Seems like other people have done the dirty work for me, and have posted up UOAs of M1 compared to other oils. I'll let their posts answer that part of your post. If you have the time, look up Mobil 1 subaru on bobistheoilguy and you'll see, Mobil 1 tends to cause quite a few problems which disappear when they switch to another oil.

If your buddy was in a Subaru, he shouldn't have been running 5w-30 at a track day. That's extremely dangerous for your motor due to the significant increase in running temperatures, which is why Mike would use a thicker oil for their track car. However, I'm sure most of us won't see temps that high daily driving, which is why I don't run such a thick oil.

 

this is borderline comedy!

SR20 let's start the Mobil 1 crew, so we can have more power to fight off the 'euro formula' 0w-30 crew.

the Blackstone lab reports reinforce my argument that Mobil 1 is a great choice for oil. Where are the numbers showing that it is out of normal spec? Also, 10w-30 is not 0w-30 and shouldn't be compared as such.

glad to see you like the Castrol, but Porsche and I will stick with Mobil 1

 

Lol! Yea I'm down, Mobile 1 Krew ftw. Hell its proven on sr20's, reccomended factory oil on the evo 4g63, heck even my diesel head roomate swears by the stuff.

 

I'm not going to comment w.r.t. "best oil". But as far as the lab comparison goes, although the car/engine is the same, it is over 1.5 years older - and the tests were done with different weights of oil. This lab comparison isn't really fair in that sense.

Ideally, you run the same weights for the same time, and go back to the first oil for a third run to compare against the first to make sure it isn't the engine that has changed.


FTR, I generally use Castrol, so I'm not trying to defend M1.

 

There is some truth to what you're saying.

I looked at the M1 5w-30 datasheet and they now spec the cst @ 100c to be 11.3. This is a tad thicker than the last time I looked it up a few year(s) ago. I recall GC sitting around 12.1 cst.

Here's the catch, viscosity is related to the temperature it's measured at. These datasheets and lab tests only give us one instance of the viscosity. Whether this one measurement of viscosity is relevant to real-world conditions is debatable. (At least for us amateurs.)

Now, a lot of other people have done their homework and it's inferred that M1 runs a tad thin and shears down whereas GC does not. It's a combination of backyard experiments, educated guessing, theory, and some lab analysis. I personally run GC based on these results, but at the same time, I won't harp on anyone that uses M1.

Finally, there's always the thicker vs thinner debate - I've never been fully convinced by either side, so I dare not even touch this subject.

 

word.

I mean I have run m1 forever and I've got over 149,000 miles on a run hard motor so it can't be all bad.

 

Dang... you know you're a nerd when you start arguing about motor oil on the internet

 

Made me LOL, your so right

 

OP: It sounds like you just didn't get an accurate reading after the change (which should take 4.8 quarts including filter).
Try this: Tomorrow morning,cold (easier to read dipstick),try to get it right on the full mark. Recheck next morning if you had to add. Then drive for 500 miles or so and check the same way. Your engine is probably fine.