Using 5w20 Oil

Don't do it. I'd guess a Subaru would likely survive through the warranty period with a 5W-20 oil, but what would be the long-term consequences?

I've heard that Mobil 1 5W-30 is pretty close to being a 5W-20 oil.

I agree. I run Mobil 1 10W-30 because it significantly reduces valve clatter on startup.

I would go with the manufacturer's recommendations. However I run 5W-20 in a Ford Focus ZX-3 and have noticed good fuel economy. BTW Ford (of America) recommends 5W-20 for it's ZTEC engines.

Subarus run lower coolant temperatures, so 5w20 might operate thicker than 5w30 in another car. You could always do an experiment, and tell us the results.

It will do nothing for fuel milage it will protect your bearings less though

I asked SOA via e-mail this question a few months ago. Their reply was the generic "refer to you owners manual" for recommended oil viscosity. In other words "don't do it."

Mike

I disagree. Ford, Mazda, and Honda seem to believe that 5W-20 improves fuel economy. Ford even has a list of 5W-20 approved vehicles going back to before they started using it.

That I do agree with. There seem to be the macho Ford F-150 truck owners who refuse to use the recommended 5W-20 oil.

My biggest problem would be going counter to the manufacturer's recommendations. Ford and Honda have extensively tested their vehicles for use with 5W-20 oil and Subaru hasn't (or hasn't made it public).

Subaru "prefers" 5w30 but if you read the manual 20w50 is preferred for towing and in 100F plus temps. I imagine that using any of the listed oils at a given temp range will not result in damage. With 10w30 my 2.5 04 OBW is quieter and mpg is the same. Since 10w30 is listed as suitable for NJ temps in spring in summer I'm not worried about engine damage especially when using syn blend oil.

I think the CAFE rules have created a somewhat artificial impetus for auto monufacturers to recommend extremely low viscosity oils to get an xtra .5 mpg during govt. testing. I've heard (anyone confirm?) that many models sold overseas with identical drivtrains to the US versions have manuals listing higher weight oils.

Carl

1 Lucky Texan

Mike wrote:

It would depend on the climate you live in. If it doesn't get really hot for long periods in the summer, then it should be fine.

I run 5-30 in the winter and 10-40 in the summer. Thinner oil in the winter will help it start easier and the oil is thinner when starting so you get better lubrication. A thicker oil in the summer will be thicker at higher temperatures and will give better lubrication.

Subaru engines have a lower operating temperatures than some. I am especially amazed at how well mine dissipates heat with such a puny radiator. I had an old AMC 360 V8 in my old Jeep that ran 240 most of the time. I didn't run anything thinner than 10w40 in that beast. In the summer I ran 20w50.

Henry

Agreed, and I'd be especially careful during the warranty period. And, regardless of what Ford, Mazda or Honda recommend, we're talking Subaru. IF (and that's ONLY if) one has an oil-related warranty problem, telling the Subaru dealer "Well, my Honda book says it's ok" isn't likely to get one too far.

Since I live in a warm climate--SoCal near the desert--the cold starting part of the equation's not as important to me as hi-temp protection. I've seen virtually no difference between 10W-30 and 10W-40 or 15W-40 as to fuel economy, but a major difference in oil pressure, which makes me a bit nervous. So I doubt any fuel economy increase from dropping to a

20 weight would be significant vis a vis the risk of engine wear if it's not mfr approved. Naturally YMMV depending on climate and other factors.

Rick

As an aside, I recall that Mobil 1 first came out in a 5W-20 weight. Mobil's rationale was that it could provide protection that was at least equivalent to the 10W-30 and 10W-40 motor oils available in the early 80's. The alleged benefits were better fuel economy as well as better cold starts.

Of course Mobil had a hard time convincing people to run counter to the manufacturers' recommendations. They used to recommend 1 year or 25K mile oil changes (with regular filter changes) in addition to the oddball (at the time) 5W-20 oil weight.

IIRC a major reason for consumer reticence lay in the fact manufacturers made it pretty clear if you didn't follow their recommendations, they did they not have to (nor would they) honor warranty claims. Lessee, now: I use the wrong weight oil in my engine, the transmission goes out and it's not covered? It would be a hard sell to get ME to change...

Rick

Well - **technically and legally** the responsibility for proving that improper maintenance led to a failure lies with the manufacturer. Practically speaking, the dealer/manufacturer might not go through the trouble if they think they have the owner with his pants down (i.e. "you used what?").

From what I understand about the early Mobil 1 was that they had a host of problems with seals leaking, but otherwise cars ran extremely well. I remember an '84 Mercedes-Benz approved oils list, and Mobil 1 5W-20 was on it, but only for colder ambient temps.

Funny, at least one manufacturer I know does not recommend 10W-40. Years ago a major oil company had a bad lot of 10W-40 get out, seems it went to something like 10W-20 real quick & killed a few engines.

5W-30 in the winter & 10W-30 in the summer for me.

Oh, also a few years back GM had a recall on cars to have the oil changed. Seems they left the factory with 10W-30 & the recall was to change them to 5W-30 because that's what they ran for the EPA tests.

Mike '01 OBW

I can't think of any current manufacturer that says conventional

10W-40 is OK for "standard" use in certain climates, except Subaru. The vast majority of US owner's manuals specify 5W-30 or 10W-30 as the preferred weight. 5W-20 is the preferred weight for most recent Honda/Ford/Madza engines. Some German cars come with recommendations for 5W-40 or 0W-40 synthetics, but those come with a specific oil (Mobil 1, etc) in mind.

My guess is that most engines can tolerate a wide range of oil weights without any kind of major catastrophe occuring for a long time. It's been established that virtually identical engines can come with different recommendations in the US compared to Europe or Asia. Whether or not 5W-20 oils can reduce the long- term life of engines hasn't been established. However - I have heard reports that oil analyses from Fords/Hondas running 5W-20 oil have shown metal wear rates similar to running 5W-30/10W-30.

Seems about right. Never underestimate the power of a recall campaign to show that the automaker "cares".

Well, I went ahead and put Motorcraft 5w20 Premium Synthetic Blend motor oil into my '00 OBW and to thicken it a bit added 1qt. of Mobil

1 T&SUV 5w40. After 1298 miles with this mix I got no change in gas mileage. Acceleration seems to be better. Once the car is up to temperature, she sounds the same...maybe even a little quieter, but thats really a subjective motion. The infamous Subaru cold start ticking is still there, no better or worse sounding, but takes longer to dissipate which bothered me. So yesterday I drained a quart out and added Chevron Supreme 10w30 to try and thicken it a bit more. Seems to have worked, the cold start ticking is still there but dissipates a whole lot sooner.

bgin