thicker oil for Subaru Wrx?

[94exa2]

Hello Bitog, I had a quick question about thickening the oil in my 2005 Wrx stg 2 with stock ej205 engine and stock td04 turbo. (yes, I know, we all hate oil questions)

A little of a back story. Before I bought my Wrx I had done a bunch of reading online and noticed a lot of people complaining about thin oils and pretty much everyone saying thicker more robust oils are better. When I bought my Wrx I read in the manual that thicker (than oe 5w30) oils are recommended for hard use. I have always (except the first change) used Mobil 1 0w40 Euro since owning the Wrx (past ~20k miles) and both myself and my Wrx seem to like it better than the 5w30 that was in it. Always changed it every 3K w oe Subaru filter.

Now comes the sort-of question. I am debating on using like half a qt of slightly thicker oil every oil change (along with ~4qts of my regular Mobil 1 0w40 euro), or just using my regular Mobil 1 0w40 for regular oil changes and using a slightly thicker oil for my frequent top upts instead of topping it off with my usual Mobil 1 0w40 euro.

Is this a good idea, even just to try it and see? The engine seems to like the Mobil 1 0w40 euro better than the regular Mobil 1 5w30, was wondering if it would like up to 1 qt of some a little thicker.

I was thinking maybe Mobil 1 5w50, Mobil 1 High Mileage 10w40, Mobil 1 Turbo Diesel Truck 5w40 or maybe something Amsoil has (one of their 5w40 euro, or other 0/5/10 W 40/50) for top offs, or maybe the last half quart of the oil change plus top offs.

Ideas? Suggestions? Recommendations?

 

[901Memphis]

The Mobil 0w40 is plenty thick enough for your turbo subie! It's probably the best choice you could make. No need to use the 15w50 at all.

 

[cutlassvillager]

My father's 02 WRX (also an EJ205) has had less consumption using Rotella T6 versus Mobil 1 0w40. I would also agree the 15w50 is probably unnecessary. I'm not sure how much you're topping off over the course of an oil change but slightly thicker top up oil probably won't make a very large difference in the long run.

 

[HTSS_TR]

Mobil 1 0W40 is plenty thick as mentioned by 901Memphis, I actually like to thin it down a little with 1 quart Mobil 1 Advanced Fuel Economy 0W20. Your 3K OCI with Mobil 1 is a little waste on the top tier oil, you can easily extend OCI to 7-8k miles. Remember that this same Mobil 1 0W40 is used in Mercedes AMG engines for 10k or longer, and in Porsche for much longer than 10k.

 

[147_Grain]

Here's a 3rd endorsement for Mobil 1 0W-40....at 5,000 OCI's on the turbo engine.

 

[Trav]

Another vote for Mobil 1 0w40. Its plenty thick enough and meets Porsche spec A40.
If it can keep a turbo Porsche water boxer alive i cant think of any reason it wouldn't work just as well in the WRX.
The engines are of similar design and HP output per ltr. Apples to Apples comparison.

Edit:
Originally Posted By: HTSS_TR
Remember that this same Mobil 1 0W40 is used in Mercedes AMG engines for 10k or longer, and in Porsche for much longer than 10k.

True but these cars have a much larger sumps and the Porsche uses a dry sump. Both help contribute to longer OCI's
IMHO i wouldn't go much more than 5K in the WRX.

 

[sicko]

I wouldn't mess with the Mobil 1 0w-40. However, if you're stuck on trying something, then use any of the Mobil 1 oils you mentioned as top up oils during your oil changes.

Also, no reason to do 3k mile oil changes. If I recall correctly, Subaru recommends 3,750 mile oil changes on conventional oil. So I'd say take the Mobil 1 up to at least 4k mile oil changes, since it can easily go at least 5k miles. Do 4k-5k miles, then do a used oil analysis and I'm sure you'll see the oil is still holding up very well.

 

[bluesubie]

If you're not seeing that much consumption/burning, I agree to just stick with Mobil 1 0W40. If you are, or just get an itch to try something new, try Mobil 1 10W40 HM (all, not mixing).

I've always burned through 2 qts in 5k intervals, regardless of what I use, so I'm thinking of 10W40 HM next. If you are protuned, then that is a plus since protuned cars usually run less rich than with an Off The Shelf map (depending on the MY) and there is less fuel dilution of the oil as a result.

I would agree that you can to farther on the interval (5-6k), especially since your 2.0T isn't plagued with oil screen clogging issues like the 2.5T's. But I'll tell you one thing. Nobody on this forum offered to help pay for my turbo failure that was from a result of extended intervals, so I can understand your reluctance to extend the oci. 7-8k intervals definitely wasn't very smart on my part, especially on an engine with known oil issues.

It was an oil with a lower HTHS oil than Mobil 1 0W40 though and I haven't run an oil with lower than a 3.5 HTHS since (except for the Subaru oil for a
I'm running a Cobb Stage I OTS map now and my fuel dilution isn't too bad.

-Dennis

 

[QuietPortage]

^ This advice is all good. Mobil 1 5w-50 or 15w-50 won't hurt anything, although a half-quart won't make any real difference.

Consider a used oil analysis sometime to make sure everything is in order.

 

[94exa2]

I was thinking about the Mobil 1 5w50 (supposedly spec'd for porche, vw, Mercedes, Bmw, Lexus), Mobil 1 High Mileage 10w40 or maybe the turbo diesel 5w40.

For some reason I feel a slightly thicker oil could be a good thing...

I dont really plan on going past 4k mile oci no matter the oil used. I "try" to do it every 3k but go a few hundred miles over quite a bit. I also check and top off my oil like once a week. I usually go through 1 quart of top off oil every 3-4k mile oil change. 1 quart at most.

Lets just say I go to walmart to get 1 quart of oil and cant find my regular Mobil 1 0w40 euro in single qt. What would be my best alternative, Mobil 1 High Mileage 10w40 or Mobil 1 5w50? (hopefully to slightly thicken up the 0w40 a bit but also be good for my engine/turbo and mix well with)

 

[94exa2]

-I dont like using "resource/energy conserving" oils. Me and the car like the slightly thicker 0w40 than the old Mobil 1 5w30, but I still feel a 5w45 (lol) would be better than the 0w40.