Custom mix 5w25 - good or bad?

[scoobie]

I have a 2008 Impreza, 2.5l NA. with 14,000 miles. Up here is Sault Ste. Marie, the winters are fierce. I would like to run Quaker State 5w20, because of the phenomenal cold characteristics of this oil, and since my engine is NA, and turbos use 5w30, my engine should be protected even with 20W - right? but... I don't want to do anything risky, so I'll mix 50:50 Quaker State Synthetic 5w30, and Quaker State conventional 5w20. this will give my engine the thin oil lube it needs in the cold, fabulous cold pour properties, and even when hot, still be similar to a 5w30 conventional, due to the synthetic component. This, along with a "maintenance dose" of 100ml of promoly (MoS2 suspension), should do the trick. Change oil every 2500 miles when exposed to dead of winter, and with a Bosch 3323 filter, for extra length, changed every other time, and I should be all set, for the beginnings of a 400,000 miler journey - I've already given my engine a good heavy promoly treatment, so all internal components should be well coated For extra safety, the engine block heater will be plugged in at night.

 

[chevrofreak]

You would be better off just using a straight 5W-20 synthetic

 

[rg200amp]

You are just diluting the synthetic and conventional oils. I would use one or the other. You would want the full add pack of the synthetic, or the full add pack of the dino.

Use the synthetic with great confidence.

 

[Steve S]

What oil viscosity is recommended in the owners manual? What are you expecting to gain by blending the viscosities? How do you know how long the engine will last 400,000 do you do lots of freeway driving or long trips? What is promoly supposed to do?

 

[rg200amp]

Too, I personally would not use a oil additive. The motor oils additives are not made to work with a shot of "promoly".

The detergents in the oil are fighting that promoly from clinging to the internals. so you have unwanted reactions going on in the motor oils chemistry while it should be focusing on protection.

 

[ZZman]

Stick with the manual for weight of oil. Use a pure Syn oil and it will be fine in the cold weather. We do we tinker around with these mixes? Do we think we know better than the car manufacturers and Oil companies?

 

[hate2work]

Forget the conventional oil, forget the promoly, just use your Quaker State Synthetic 5w-20 oil and forget about it

2500 mile OCIs will be a piece of cake for that oil, but you're just gonna muck it up by adding/mixing with it.

 

[chevrofreak]

A 5w30 synthetic would be better, and it will generally have better cold flow than a 5W-20 conventional. Most Subaru's call for a 5w30, so that's what you should probably run. The 5W-20 would probably work fine if you live in a very cold area that gets below -20C and stays there for a long time.

I'm running Valvoline SynPower 5w30 in my moms 2002 L.L. Bean outback (H6 3.0) and it seems to like it. It's still cheap, too, at $19 for 5 quarts at Walmart.

 

[Audi Junkie]

0w-30 is thinner than 5w20 conventional at 0f.

 

[ryan2022]

hmm, The synthetic will handle the summer heat every bit as good as the dino, and generally synthetics perform better in the winter. I would look for an oil in the recommended weight that had the best cold flow protperties and stick with it year round. I wouldnt mix the two different weights. Not that you couldnt, I just dont think it would be beneficial.

Most 5w30 synthetics or blends, will flow VERY well at over -40. If it gets colder than that where you live, may God be with you.

 

[scoobie]

This is a Subaru Impreza 2008 NA with a 2.5l flat four and premium package.
I am using the mixture, because I want to save a few bucks by mixing conventional and synthetic -- since the pour point of 5w20 conventional is -37C and 5w30 synthetic is -48C mixing the two will still give a really good pour point. The pour point of 5w30 conventional is
only -33C, very poor. Because I'd like to economize by using a 50:50 mix, then using a conventional 5w20 is more optimum for my harsh winter, where -20C occurs regularly, and -30C can happen. The Cst for synthetic 5w30 is 11.3 at 100C whereas the conventional 5w20 Cst is about 8.8, so the blend at 100C will be more suitable for engine protection, about 10, close enough to Cst of 5w30 conventional. Because my engine is very new, all of the tolerances are tight, and I want something thin to flow between the bearings, etc., without having to cough up the dough for 100% synthetic each time. I am trying to be frugal, yet smart. I am using the Bosch 3323 because it is longer than the recommended filter, so I can change it every other time, and since I am not running a turbo, and it is still not too close to the exhaust pipe, there is no danger of coking the oil. This will save me $2.50 per oil change, and I save +$5.00 on the oil, so a grand total of $7.50 saved per oil change. That's about $37.50 per year I save, which means I get 5 oil changes for the price of 4, and enough left over to buy 2 crush washers.

 

[rg200amp]

Personally I would never mix two oils. You are just diluting both oils.

Use just the Dino or just the synthetic.

Or buy a middle priced Blended oil.

When you mix it yourself, both oils additive packs cant be used to there full potential.


Also, I would personally change the oil filter every oil change.
The way I see it= Clean oil going through a dirty filter makes the clean oil dirty. The opposit of what you want to do.

Plus that extra big filter(pending on the way it is layed out) could be holding a extra quart of dirty oil in it when you do not change it.

 

[scoobie]

That might even be better, use the conventional 5w20 in the super cold, when I need to change more frequently, and then use synthetic 5w30 when it starts to warm up, when I can keep the oil in longer. Saves even more money.
So is there any problem running Quaker State 5w20 conventional in a flat four NA Subaru in the middle of winter? The manual calls for 5w30, but 5w30 oil is even good in the turbo engine, in the middle of summer, the demands of an NA engine are less - right? -- it should really love the conventional 5w20, especially compared to a 5w30 conventional, when it's -20C outside. I mean, we know better than the manufacturer, right?
That's why I love this forum, all the experts here that know what the manufacturer really SHOULD have put in the manual, but didn't understand oil enough to do it.

 

[HTSS_TR]

Originally Posted By: scoobie
... The manual calls for 5w30 ...


You should use 0W30 year round for warranty purpose. If you use xW20 in winter and need warranty work on engine, dealer may have reason to not honor warranty for using wrong oil.

After warranty, you may use 5W20 for winter and 0W30 for the rest of the year.

 

[Saturn_Fan]

Originally Posted By: HTSS_TR
Originally Posted By: scoobie
... The manual calls for 5w30 ...


You should use 0W30 year round for warranty purpose. If you use xW20 in winter and need warranty work on engine, dealer may have reason to not honor warranty for using wrong oil.

After warranty, you may use 5W20 for winter and 0W30 for the rest of the year.


+1, I have been confidently using AMSOIL Signature Series 0w30 in some pretty cold temps up here in Northern Wisconsin with great results. Heck, I even use it in my snowblower.

I realize that the temps here are definitely not as cold as where the OP is, but I see -20F here.

The OP should just run a block heater and a 0w30 with no additional additives and call it a day.

 

[rg200amp]

+1 on 0w30 all year around.


You can do it your way, dino in the winter, synthetic in the summer. it will work.

I would use one oil all year round. so the 0w30 would be the best.


Plus, synthetic flows way better in the winter than the dino.

 

[demarpaint]

Another vote for 0W-30, either PP or Mobil 1 what ever the OP can find locally and at the best price.

Frank D

 

[chevrofreak]

Put 5w30 synthetic in during the summer, and it will have sheared enough by winter that it will probably be a 5W-20.

Run a longer oil change interval than you would on conventional and you'll break even.

 

[Al]

I think with the price of gas what it is and the cost of your relatively new vehicle..seems lame to look at saving a couple bucks. Go with the 0w30 and run it out longer.

The 2.5 NA's are super easy on oil. You can easily run 10,000 miles on it.

 

[bob_ninja]

Originally Posted By: scoobie
That might even be better, use the conventional 5w20 in the super cold, when I need to change more frequently, and then use synthetic 5w30 when it starts to warm up, when I can keep the oil in longer. Saves even more money.
So is there any problem running Quaker State 5w20 conventional in a flat four NA Subaru in the middle of winter? The manual calls for 5w30, but 5w30 oil is even good in the turbo engine, in the middle of summer, the demands of an NA engine are less - right? -- it should really love the conventional 5w20, especially compared to a 5w30 conventional, when it's -20C outside. I mean, we know better than the manufacturer, right?
That's why I love this forum, all the experts here that know what the manufacturer really SHOULD have put in the manual, but didn't understand oil enough to do it.


Speaking of costs, you should mention our filters are $10+ (a decent one) and M1 is $40+ compared to dinos are found for $10-$16 So in Canada differences between dino/syn or changing filters less often can add up to more $ than in US.

All my cars are 5W30 according to manual. While I started mixing in a single litre of 5W20, I would not be comfortable with going all 5W20 even with your temps. In particular:
- during snow storms we spend more time at lower speed and idling, so engine can be hot
- driving through deep snow can actually put a lot of load on an engine while speed is low (due to high resistance and safety)

So you could use some 5W20 *BUT* not 100% 5W20!!! That being said, if your trips are short and engine never gets up to full operating temperature then sure.

Another thing to keep in mind is thin thick 5W20. For instance our Formula1 5W20 which I think is from Shell I am guessing would be thin version compared to Castrol GTX which is a very thick 5W20. Thus I put Castrol GTX 5W20 into my older engines calling for 5W30 while thinner F1 5W20 into newer engines. Again, in my case no more than 33% 5W20 mix.