Mobil 1 says when driving under normal conditions, using their extended performance filter with their extended performance synthetic oil, that you only need to change your oil every 15,000 miles. This sounds almost too good to be true. Can someone with knowledge on this lend your opinion? If you don't feel comfortable with 15k then how about every 10000 miles. I drive my 09 Subaru under normal conditions and have currently been using regular Mobil 1 5W-30 oil and Mobil 1 filter and changing my oil every 7000 miles. Thanks for your input.

5/15/2012 10:31:35 PM

I use rotella T and change every season, ~4000 miles of WOT/redline with k&n (on bikes) or 10-15k with a purolator filter without problem.

5/15/2012 11:17:32 PM

what subaru? and i do not recommend extended change intervals on Subarus, i have see too many sludged up. Traditionally in my experience at a Subaru specific shop i would not run Mobil 1 products in a Sub, especially the turbo ones. If it is a Turbo model stay on the 3750 that is recommended in the manual as the turbo is hard on oil. If it is naturally aspirated then I think the interval is 5000

5/16/2012 6:21:59 AM

^ what he said.

I use rotella t6 synth and yep... my turbo lets some of thin oil by on extreme cold days (mhi td06 20g) but i have one of the happier 2.5s i've driven/ridden in. Its also an extended life oil... and i NEVER let it go past 5000 miles on an oil change i usually change it around 3000.

5/16/2012 6:46:32 AM

I'm glad some Subaru guys chimed in b/c I know nothing about them. However in my Hondas I go 8,000-10,000 miles with regular Mobil 1 without a second thought.

5/16/2012 9:17:53 AM

I think its part the flat motor setup, part the journal bearing turbos, but the combination cooks oil quickly and doesn't tolerate cooked oil every well.

5/16/2012 10:15:52 AM

best bet would be to spend $20-30 on an oil analysis and check the total base number (a measure of the life left in the oil)

if you are going to go 15k on the oil, you should probably replace the filter halfway through. too many contaminants in the oil can clog up the filter causing the bypass to open, basically making the filter useless and pumping all that crud back into the engine.

5/16/2012 12:35:50 PM

yep...that works great... or you could listen to people with your same engine and a history with them including building a crap ton of them like markvii and know that like it or not your subie will burn some oil and not checking it till 10000 miles you're probably going to run low enough to cause some issues and regardless of the quality of the oil you'll need to change it way before it tells you too.

My buddy runs a full ams-oil kit on his and still changes his oil at 3500 and it needs to be done. (checked by oil analysis)

Also.. for some reason mobil 1 seems to spin subie bearings... i don't know if it's detergent cleans things out and loosens them up or what but it seems to be a trend.

Also my experiences and i'm pretty sure mark viis are both with turbo-subies.

you people with your well built german cars with tight clearances and proper drainage back to the oil pan think that your oil knowledge translates just fine... it doesn't... ask bigT.


[Edited on May 16, 2012 at 1:03 PM. Reason : .]

5/16/2012 1:01:29 PM

fwiw, i wasn't recommending a 15k oil change. i always change mine at 5k. and you can say tight clearance and german all you want, but the AEB 1.8t in my car was notorious for sludge issues. i have 2 junk cylinder heads (fucked cam journals), most likely caused by using conventional oil or trying to extend the OCI either through neglect or some half-assed notion that it would be ok, like the mobil one commercials that say you can go 10-15k on an oil change.

i don't ever recommend it, but if someone really wants to try to extend their interval, i figured i would at least let them know what the right way to do it would be.

5/16/2012 6:01:52 PM

i do 15K on my wife's highlander, 10K on my '07 duramax & '90 cherokee.

i have had an oil analysis done on the oil from the wife's car which had 15K and the oil still had a TBN of ~4. the company said going longer was fine but i decided to stick with 15K since it's easy to remember when the next change is due.

i do 10K on my truck and jeep for separate reasons. on my truck i do not feel comfortable carrying the oil to 15K due to soot even though the analysis company says i can and the fact mobil1 doesn't sell EP in 5w-40. same for the jeep, i run 10w-40 in the winter and 15w-50 in the summer and neither are available in the EP.

this is the only report i have uploaded and is for my truck. next analysis i have done i'll upload that as well if you'd like proof that mobil1 really is good for 15K.




[Edited on May 16, 2012 at 8:13 PM. Reason : -]

5/16/2012 8:10:20 PM

Thanks for all the input folks. My Subaru is not a turbo, regular 2.5L Forester. Rotella T6 seems like overkill but I get that I shouldn't use Mobil 1 any more. Any other oil/filter suggestions with appropriate change intervals?

5/17/2012 12:30:43 AM

if mine wasn't a turbo i may let it go to 10k miles.... i dunno...

5/17/2012 6:40:47 AM

if mine wasn't a turbo i may let it go to 10k miles.... i dunno...

5/17/2012 6:40:47 AM

Yeah Subaru seals (cam and crank) tend to not like mobile 1 for some reason.

i want to say the NA 2.5 forester had a change interval of 3750 or 4250? jsut check the manual.

Stay away from fram filters, not necessarily for filtration purposes but due to the internal bypass being wrong for the subaru. The OEM filter from the dealer, or an online source has tested very well.

A lot of the oil concerns on a subaru come from it being a boxer motor so PCV (crank case ventilation) is more of an issue, as is the fact that oil drainage throughout the engine if slightly different from a standard upright V or inline. Use a quality oil, and keep it changed at the correct interval and it wil be fine.

Unfortunately odds are good it will eventually need a set of head gaskets, as the NA motors do se that as a common failure item, but they can be done at the same time as the timing belt to keep costs a tad lower.

5/17/2012 6:46:40 AM