2010 Forester NA 2.5L - Summer oil

[nepadriver]

Subaru manual recommends 5w-30 but also states "Engine oil viscosity (thickness) affects fuel economy. Oils of lower viscosity provide better fuel economy. However, in hot
weather, oil of higher viscosity is required to properly lubricate the engine."

That being said they list 5w-40 as also acceptable in the -40 to 50 Celsius range (-30 F to 110 F range). Other oils listed are 10w-30 10w-40, 10w-50 for -20 C (0F)to 100+ range.

Question, I've been running 5w-30 PU since November in northeast PA, mild winter. Summer can hit 90-100F easily, especially in July and August. Would I benefit from a 5w-40 and/or any of the 10 weight oils listed in the manual? And by benefit I mean better protection for engine in hot weather. I only put 400 miles a month on the car, will be taking a 560 mile highway trip in early Sept. probably 80% city miles normally.

My understanding was that with liquid cooled engines the need for "heavier" oils in hot weather was negated, according to Bob's Oil U lesson 2 or 3 I believe. If so why did Subaru put that in the manual?

 

[gathermewool]

5W-30, year round is my suggestion.

 

[nepadriver]

Thanks Matt, that is what I've been doing. Its odd that Subaru mentions heavier oil for hot weather when BITOG Motoro Oil 101 says "One thing that is no longer important is the ambient temperature. Older automotive owner manuals often recommended one oil for the summer and another for the winter. This is still necessary for air cooled engines but is no longer a consideration in pressurized water cooled engines. These engine blocks are kept at around 212°F all year round. The oil is around the same temperature as well. This allows for a single grade oil all year round. Again, this is not the same as on the track where the coolant temperature is slightly higher and the oil temperature is much higher."

Here (it was Chapter 1 actually):
http://www.bobistheoilguy.com/motor-oil-101/

 

[edhackett]

The oil temperature gauge that I had in my WRX says the information in the Motor Oil 101 is flat out wrong. The bulk oil temperature tracked the ambient temperature + 100F from about 40-100F.

There is a lot in MO 101 that is misleading or not complete.

Ed

 

[nepadriver]

Originally Posted By: edhackett
The oil temperature gauge that I had in my WRX says the information in the Motor Oil 101 is flat out wrong. The bulk oil temperature tracked the ambient temperature + 100F from about 40-100F.

There is a lot in MO 101 that is misleading or not complete.

Ed


Thanks Ed, so would you say 5w-40 or 10w-30/40/50 would help lubricate the engine better during ambient July/August temps of 90-100 F versus 5w-30 year round ?

 

[chainblu]

You are probably over-thinking this. Two months of 90+ degrees is nothing to worry about. The 5W30 you are running now is plenty capable of protecting at those temps with conventional oil.

 

[Eddie]

5W30 WILL BE BE THE BEST CHOICE IN MY OPINION. ED. Ops-cap locks-sorry

 

[edhackett]

Actually, maximum oil temperatures are pretty well controlled in Subarus. The oil temperatures that I saw indicated that a sturdy 30(ACEA A3 or HDEO) or a 40 on the thin side (M1 0W40) were fine in the summer seeing 100+ but less than 110F temps. I run a 10W-30 that meets ACEA A3 viscosity specs. that has a HTHS of >3.5(Rotella T5) year round in my 2008 Legacy GT. Yours being NA, has less of a heat load.

I think a quality synthetic like the PU in 5W-30 that you have been using is fine for your temperatures. If you were turbocharged, towing, tracking your car, or using a a conventional oil, I'd be more inclined to step up to a ACEA A3 10W-30 or 10/15W-40.

As a side note,I put 200K on a 1995 Outback 2.2 using Delo 400 15W-40 year 'round here in Reno. It was running as good and used the same amount of oil when new when I sold it.

Ed

 

[Bandito440]

5w-30 is a good choice where you are. I would consider xw-40 in much hotter places or if your vehicle was modified, raced, or turbocharged. I lived in Yuma, AZ for a bit and the Subaru guys I knew ran Rotella T6 year-round there. My friends in the Northeast who race their turbo Subarus do the same.

That being said, it is your vehicle. Rotella T6 5w-40 or Mobil 1 0w-40 should be just fine. It won't hurt anything. If it works for you, do it.

 

[WagonBoss]

The EJ engine is easy on oil. Consumption and/or volatility of lighter oils is another issue. If you check frequently and top off and are ok with adding then 5w-30 is fine. I prefer an oil that stays put. Any of the heavier oils in the manual will work fine. I've run straight 30, 15w-40 and 10w-30 oils in my two with no scientific difference in fuel economy. Speed makes more difference in MPG. I believe Subaru allows the other viscosities because they work well at the extremes. For normal everyday driving they aren't required.

 

[bodeh6]

I run 5W-30 year round here in 4 season Michigan. My Legacy is 6 years old and still runs great. Been doing 6 months/5K miles OCIs with synthetic for about 3 of those years. Works great.

 

[bluesubie]

I agree with sticking with 5W-30 in an n/a Subaru. They've done very well in my '00 2.5RS and '99 Outback. Try 10W-30, if it makes you feel better, since it "should" be more stable. I would also go the full 7,500 mile normal service interval as well since you're running synthetic.

-Dennis

 

[tenderloin]

We have a 07 Impreza 2.5i that has been passed down to two children as they attended university. I use 5W-30 or 10W-30 and the car runs great. It now has over 105,000 miles. I used 5W-40 once or twice but noticed a hit in MPG as well as performance.

 

[nepadriver]

Originally Posted By: bluesubie
I agree with sticking with 5W-30 in an n/a Subaru. They've done very well in my '00 2.5RS and '99 Outback. Try 10W-30, if it makes you feel better, since it "should" be more stable. I would also go the full 7,500 mile normal service interval as well since you're running synthetic.

-Dennis


We'll that would mean I did my first oil change at 1.5 years old

only at 8300 miles and won't be 2 years old until July. It does mostly 5.5 mile trip one way to work, city driving short trips. I currently do twice a year, November and May.

 

[edhackett]

That is soundly in the severe service category. Stick with the short/2X a year intervals. If you're not opposed to using an oil that stretches the recommended certifications, being SM only, the Rotella 10W-30 T5 could save some money and give as good, if not better protection against fuel dilution in your short trips.

If the cost isn't an issue and you want to stick to the PU, that's fine too. It would likely be my choice for a 7500 mile OCI under normal driving conditions. The 10W-30 is just a touch stouter than the 5W-30, so you could do 5W-30 in November and 10W-30 in May. Given the majority short trips, 5W-30 would be fine all year.

Ed

 

[gathermewool]

Originally Posted By: edhackett
That is soundly in the severe service category. Stick with the short/2X a year intervals. If you're not opposed to using an oil that stretches the recommended certifications, being SM only, the Rotella 10W-30 T5 could save some money and give as good, if not better protection against fuel dilution in your short trips.

If the cost isn't an issue and you want to stick to the PU, that's fine too. It would likely be my choice for a 7500 mile OCI under normal driving conditions. The 10W-30 is just a touch stouter than the 5W-30, so you could do 5W-30 in November and 10W-30 in May. Given the majority short trips, 5W-30 would be fine all year.

Ed


I'll second something like the Rotella T5.

To your earlier comment, I wouldn't try to compare peak oil temps between a N/A and turbo Subie. Our peak temps will be much higher during aggressive driving than his.

 

[fdcg27]

I used GC in our Forester for a while thinking that a thicker oil might better suit it.
The car is now on its third run of thinner Valvoline, based upon what I saw of NA Subie UOAs in that forum.
I will UOA this run, and the only reason I'm even using a 10W-30, rather than a 5W-30, is that I picked some up cheaply, and am using it during warmer weather.
The car had Synpower 5W-30 December through March.
There is a member here who is fond of saying that these engines would run fine on urine.
By this he means that NA Subies are not picky about oil, although they may shear it somewhat.
After all of that, run a thirty grade year 'round, and your engine will be just fine.

 

[bluesubie]

Originally Posted By: fdcg27

There is a member here who is fond of saying that these engines would run fine on urine...

No names (to protect the guilty), but he has run SuperTech 5W-30 to 10k intervals (or longer?) in his n/a Forester with good uoa results.

-Dennis