So I’ve been told that 10w-30 oil would be best for my 1986 gl wagon. But I can get 5w-20 oil much easier

Would it be much of a difference if I used the 5-20 instead of the 10-30?

You might void the warranty… ok I’m just kidding. 
 

I don’t think the engine will have any catastrophic event using that oil. But I’ll let you know what I heard growing up. We would be content using Castrol - “engineered for small car engines” - marketing spew. We would use 10w40 in winter , and 5w oil in the summer. 
 

Pardon me if I didn’t research on 5w/20 but I’m assuming it’s a more thin viscosity than the 10w. 
 

Generally as my Subarus got up in miles I would use the heavy weight oil pretty much all year. If you’re engine is really tight and not so worn then Yes you do notice a little sluggishness if you use heavy oil in winter. But that was probably only one or two of the many Subarus we have run. 
 

We enjoyed many Subarus of the EA era. The EA82 dual range is still a favorite of mine. But I’ve put all that era behind me quite a while ago. 
 

I keep 70’s Subarus going. Good luck keeping the 80’s going ! Enjoy!

Depends on your driving and where you live. Long trips?  High speed? Cold winters, Hot summers?

From an owners manual: "Caution: SAE 5W-30 is not recommended for sustained high-speed driving".

From the oil chart, 10W-30 will cover you from below zero to 90 plus degrees F. Oils have changed over the years and so has your engine. EA82? An EA82 with high mileage likes thick oil. Don't freak out about the 'high mileage' term. You can take apart an EA82 with 250,000 miles on it and still see the hone marks on the cylinder walls.

I use Castrol 50W in summer and 40W in winter. I don't do synthetics for my EA82.  I am not in a hot / cold climate. Finding 50W Castrol is becoming difficult.  Engine oil is a gut call and has been discussed ad nauseam.

If you have to have oil shipped to you, check out 'ROCKAUTO.COM' for conventional oils.

Good luck.

 

Read the owners manual. You can run any reasonable oil. It would be fine. I’d probably avoid 5W on EA engines but for no reason. For what it’s worth GDs shop superior in Portland runs 5w-40 synthetic as a rather standard oil for various non turbo applications, I think including EA engines. Of course hotter temps will be less ideal for thinner oils and that’s a good reason to check the manual like prior post mentions. 

Edited February 25, 20242 yr by idosubaru

It depends on your winter time temperatures.  If you regular drop below 20 degrees F in winter, then that 5W -20W would be a good oil in winter.  In summer, back to the 10W-40W for me.

@GeneralDisorder What do you recommend for EAs?  I think ideally, one should run an oil with high ZDDP additives, or an oil designed for flat tappet engines.  The viscosity is more about temperature, but the additive package is important to consider as modern engines generally have a lot less friction than a 40-year-old design.

Do we raise a stink so all box stores carry Classic Castrol ? (With zinc)
 

I’ve found it at only a few of the many stops I’ve made. 

18 hours ago, carfreak85 said:

What do you recommend for EAs?  I think ideally, one should run an oil with high ZDDP additives, or an oil designed for flat tappet engines.  The viscosity is more about temperature, but the additive package is important to consider as modern engines generally have a lot less friction than a 40-year-old design.

run whatever you want, they're dead men walking anyway? 

 

and hey I get it, it's not like it's easier to daily drive my XT6 than our 2016 outback. 

The whole need for ZDDP thing is highly over exaggerated. Unless you are running high pressure valve springs and a radical cam, you'll have no issues with about any oil you throw in an old flat tappet engine. Pick an oil viscosity based on your climate and go drive . I have 7 vehicles with flat tappets including an 87 DL (247K miles) , 87 B2000 (302K)  and five 65 Corvairs (all over 150K). I've owned most for over 25 years and pay little attention to anything but viscosity. I run 10W-30 in the mild winters here and 10W-40 in the hot summers. I run 50W in the Corvairs that only get driven in the summer.