WillisW555

iTrader: (1)

I hope this is the right forum for this. I am contemplating some service on the car and my friend called Subaru to ask some questions. In the course of the call, he was told that Mobil 1 or other synthetic oils are bad for the engine.

The customer service rep said that according to the engineers, synthetic oil is TOO slippery and won't absorb into the seals. Thus causing them to dry up and leak. They also changed the interval (on regular oil) to 3,750.

That doesn't even make sense... I've never heard that synthetic oil is bad in that sense. I have heard that Mobil 1 tends to be consumed by the engine at a higher rate than other oils. I see less than 1 quart consumption over the 7,500 oil change.

I likely still get redline for the gear oil/tranny. I have 2 cases of Mobil 1 motor oil so I'll probably want to just use that up unless it's actually BAD for the car.

Opinions? Proof?

PikkaGTR

iTrader: (4)

I think using synthetic in the engine is ok but you might want to stick with OEM for the diff/tran

jinorazi

i hear that synthetic is bad also...i got oem for the back and redline something something 90ns for the front diff/tranny, all from subaruparts.com

JelloChex

iTrader: (6)

Ask those people to show you proof that synthetic oils are bad. The best way to measure to see how well your oil is holding up is to do a UOA (Used Oil Analysis). Blackstone Labs can take of this for you for about $22.50/test (they will even send you the free sample testing kit).

As for Mobil 1, I used to run in my previous car and ran in it the WRX for about 50-70K miles. I finally switched over to Amsoil when I noticed drastic oil consumption. When I switched over to Amsoil, there was much less oil consumption. The problem with Mobil 1 seems to arise in the fact that it sheers down from a 30w to about a 20w or so. However someone over on NASIOC was showing a UOA where they mixed about 4 quarts of 5w-30 with 1 quart of 15w-50 and with that combination the Mobil 1 held up very well. If you still have the 5w-30 Mobil 1 I would suggest giving that a try to see if it helps reduce your oil consumption issues, but definitely recommend sending your oil in to do a UOA. The UOA will help give you an idea of how your engine is holding up, if there is any abnormal engine wear, how the oil is holding up and if you should be changing you oil change interval.

subie OCD

iTrader: (11)

There is absolutely nothing wrong with using synthetic oil as long as it meets the requirements in the owners manual. Also, flukewrx made a good point - the only real proof would be a UOA and see how the results come back. Mobile 1 does tend to be a light 30 weight oil and I choose not to use it (however hundreds of thousands use it with no issues).

As for me, after much research on NASIOC and bobistheoilguy.com I choose to use Castrol 0w30, European Blend (says made in germany on the back, aka GC, German Castrol). This oil gets great oil analysis on Subarus - it flows good in the cold, yet has been tested to be almost a 40 wieght oil. Its tough to find but some AutoZones carry it.

No matter what oil you choose, make sure it meets the owners manual requirements and ALWAYS check the oil level, Turbo Subarus are known to burn oil. As long as it has plenty of oil, there shouldnt be much to worry about

mokeOne

iTrader: (14)

weird, when i took my car in for an oil change, they (mechanics at the subaru dealer) said that they use mobil 1 syn, and that royal purple is also recommended. i used rp in my wrx (engine, tranny & rear diff) and it ran great, shifted a little smoother and got almost 1 mpg more.

WRX409

After alot of research I wouldn't put synthetic motor oil
in your Subaru.It will give you an oil consumption issue
just like it did with my 04 WRX.
I found that regular dino or "blend" 50/50 motor oils work
so much better in Subaru's.I was using Mobil One 10W30
and after one month my dipstick would be bone dry with almost
no oil in my engine.Don't let your engine run low on oil because
it will cause scoring of your crankshaft and camshaft so check your dipstick.
I am currently useing Castrol Syntec Blend 10W30 now and
my Subaru barely uses any oil at all between oil changes I really
like useing this oil.
My local Subaru Dealership told me the same thing that all
synthetic motor oils are bad for your engine.The local Subaru
Dealership by me only uses regular dino Castrol GTX motor oil.

wrxisthebest

iTrader: (15)

i use mobil 1 10w-30... and i get very little oil consumption and i have 94k miles on my motor...

WRX409

I only have 60K miles on my 04 WRX.When I was using
Mobil One 10W30 my oil was practically evaporating from
my engine.I had my engine checked out by Subaru and they
told me their was nothing wrong was my engine and to stop
useing any synthetic motor oil.They even said that if my engine
got catastrophic failure and found that I was useing any synthetic
motor oil my warranty claim would be voided and I would be purchasing
the new engine.I am using Castrol Syntec Blend 10W30 and
I have had great luck with it so far.

ApexAssassin

I've got four boxes of Mobil 5W30 syn, and it is the only oil I've used since I got the car almost two years ago. However, my car has rather low mileage, so I have yet to notice any recurring problems, if there are any. Oil consumption does not seem to be a problem, but I wouldn't have anything to compare my current situation to. I would suggest the UOA for anyone who might want more details. I'll keep using the Mobil for now, especially since I already have it.

Bro-Gnar

Mobile 1 is one of the best synthetics ever made. I have used it on all of my subarus. Oil consumption on a turbo is normal. Excessive is not. If your sub is using that much oil, it is most likely a bigger issue. Mobil is very thin and when its ran on a hot engine it can seep through the seals. same with any synthetic. Run a oil catch can! Thast way you can see how much is really blow by and how much is consumed. Mobil 1 comes stock in evo's, all porches, aston martins, etc......... I would run nothing but! Just cary a quart with you. Performance comes with a price.

kYLEMtnCRUZr

iTrader: (6)

i use mobil1 full syn 10 30 in my 2.5RS, and i constantly have to check the oil. Dipstick is dry 1/2 the time, mainly because Subaru cant design a accurate dipstick. So i check it in the AM w/o starting it up and yeah its usually low.

Ive been wondering if i should switch oils. plus $7 a quart is a bit cha