15W50 to quiet piston slap in 98 obw?

try an Xw-40 first

The only 15w-50 oils that I know of are Mobil1 and Chevron synthetics, and these can trigger leaks if gaskets are weak, so watch out. You may want to try dino X-40, or even 20-50 instead, and if you don't live in Minnesota, or some cold mountainous location.

I've had good results quieting piston slap with single weight oils straight

40, 50, Valvoline but these were used in V-6 GM engines in hot Southwest locations (example: summertime Phoenix). I think Japanese engines may not like stuff that extreme but you may try a straight 30 dino (in above freezing ambient temps). The thicker oils don't drain off of cylinder walls, rings, as fast thus help quiet piston slap at start-up. 5w-30 is very thin stuff for an engine with 170k miles.

M.J.

Would 10w30 provide any noticable improvement, or would I need to go for something more drastic?

Try Chevron Delo 15w-40 diesel type universal oil, available at Walmart and many other places. It is very refined, excellent quality oil, almost as pure as synthetic and provides mild cleansing action. Good, safe and inexpensive stuff for an older engine like yours.

M.J.

Here is some more info on Chevron Delo 400.

M.J.

AgreedL 15w-40 (I use either Mobil or Castrol) is a nice oil for heavy duty engines, and it's what I use in my 98 Audi A4Q 2.8liter

5sp, now at 110k miles. The 99 Subaru Legacy OBW still eats 5w-30, which seems ok for it.

what about Shell Rotlla 5W-40?

Doesn't anyone know about STP anymore?

As far back as I can remember, my Subaru manuals have stated specifically, do not use 5W30 oil for sustained high speed driving and then only when suitable low temperature conditions are present. Unless Subaru has since changed the recommendation for '98 or newer engines, would this not be at least a tiny concern to anybody?

My '89 GL Turbo used to have plenty of noise until it warmed up sufficiently. I ended up having best results with is Amsoil 10W30. However I also came up with a creative variety of oil solutions just for the entertainment of it all, which also worked quite well to quiet the noise and cut oil consumption. The quietest mix only had two real quarts of cheap

10W40 in it with the rest comprising generous amounts of Marvel Mystery oil, motor honey, and various other additives to bring it up to the full mark, and yup, they were all in there at the same time. Was fun to experiment with the ratios, and then feel and hear the results. The death of the motor wasn't related to oil, so no worries there. The motor died because it blew the turbo coolant inlet line and dumped the contents of the radiator while I was away from the car knocking on somebody's door to go to work, munched the head gasket(s) and warped the head(s), all before I got back in and realised something wasn't right. Was an interesting sort of catastrophic failure to come back to the car and find; and I can laugh about it, now. The coolant evacuated the system so quickly the temperature gauge never even rose past 75% of the way up before it stopped measuring altogether. Ended up with a cracked radiator before the ordeal ended.

Anyway, my Subaru manuals lists several straight motor oil weights you can use, and mentions multi-weights up to 50, but since my manual is not specifically for your motor, I would recommend looking in your own for the details you're seeking. Also, I've been told by mechanics that, if I want a

10W40, don't. Instead go with 10W30 or 15W40, as either of those contain far less friction modifiers. From my understanding up to 25% of 10W40 oil is used in just getting the viscosity to stay where it belongs. But I'm hardly an expert, so always do your own research the best you can. (-;

~Brian

My 01 outback manual is open in front of me. They show an api service label for SJ/SH service with teh words "energy conserving ii", and SAE

5W-30 as the general recommendation.

For "severe driving conditions" in high temp and desert areas, or for heavy duty applications such as towing, they recommend SJ or SH classification with SAE 30 SAE 40 10W-50 20W-40, or 20W-50.

-- Todd H.

2001 Legacy Outback Wagon, 2.5L H-4 Chicago, Illinois USA

Chevron states that Delo 400 15w-40 oil is good for engines with shorter piston crowns. Aren't short pistons in general the reason why many Subaru engines experience piston slap?

Here are some quotes, first from Subaru then from Chevron:

Through experimentation, the engineers at Subaru discovered that a slightly barrel-shaped piston produces less friction, vibration and noise. The engineers then focused on improving the piston skirt (the lower part of the piston that makes contact with the cylinder wall). In a radical break with convention, the skirt was made shorter and thinner to reduce weight.

and

Applications Chevron Delo 400 LE SAE 15W-40 is a mixed fleet motor oil recommended for all naturally aspirated and turbocharged four-stroke diesel engines and fourstroke gasoline engines in which the API CJ-4 grade and SAE 15W-40 viscosity grade are recommended. It is formulated for engines operating under severe service and a wide range of climatic conditions. Chevron Delo

400 LE SAE 15W-40 is excellent for use in new advanced engines developed in response to 2007 emissions standards and in engines equipped with features like four-valve heads, supercharging, turbo charging, direct injection, shorter piston crowns, higher power density, intercooling, full electronic management of fuel and emissions systems, exhaust gas recirculation, and exhaust particulate traps.

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M.J.

I just bought 5 quarts of max life 10w30. If that doesn't improve things any I'll step it up to the 15w40. My Subaru manual recommended either 5w30 or 10w30 so I figured I'd try that first.

I doubt 10w-30 is going to make any difference but there is logic in taking a step-by-step approach and progressing if need be. Please update us on your results.

M.J.

I, too have a 98 OBW. My mechanic recommends that all cars with 100K+ miles use a 20W-50W motor oil. I have been using Wal-Mart house brand oil of that weight for some time during warm weather. Car runs just fine. I live in Indiana, in the winter, I switch to 10W-40 for cold weather. Engine runs without complaints. With engine wear in any car beyond 100K miles, it is good to use the heavier weight oil to compensate for engine wear causing looseness inside the motor. Just my

2 cents worth.

Sorry it took me so long to update - I've been really busy. I decided to go for 15W40 instead of the 10w30 and noticed an improvement. The slap goes away much quicker now - about 2 minutes instead of 10.

Hi,

I've been away for a few weeks and am just getting caught up on your "adventures." What oil filter are you using? Over the years, we've had many discussions of "lifter noise" at startup (before piston slap became problematic) and most posters, myself included, have found some oil filters to be better/worse in this department. Suggest OEM filters (made by Purolator in the US, but slightly different than what you get at the auto parts store, though the PureOne is probably very close), followed by Wix/NAPA Gold (same filter as far as anyone can tell, just rebadged for NAPA.) Not to badmouth anyone's brand, but "orange" filters (and their many rebadged clones) seem to be more problematic in this department. A combo of 15W40 (my choice was Delo 400 for my '90 Loyale that finally died, of a non-oil related malady, at 360k miles) w/ a bit of filter swapping might cure most of your problem.

Good luck--sounds like you're on the way!

Rick

Here's a nice bunch of pictures from a NASIOC thread illustrating filter quality issue.

Thank's to the OP for the follow-up on his oil remedy.

I recently started using NAPA-Gold for my '00 Impreza (previously OEM filters). The Napa Gold 1334 is supposed to be an excellent filter composed of a mix of synthetic (glass) and cellulose media, with outstanding oil flow properties. I think it may be a good complement for a thicker oil (I am using Mobil 1 15w-50 mixed with Mobil110w-30 at 50/50 proportions), and it may be helpful for start-up piston slap issues. Supposedly, it does not filter the smallest of smalll particles as good as a a Purolator PureOne, or Mobil1, but is not as restrictive as these two. There is always a trade-of between good filtration and good oil flow.

M.J.

Hi,

Looks like another guy got a cutoff wheel for his Dremel tool and has become an oil filter expert!

Pix like this have been circulating for quite some time, and while they DO illustrate certain cosmetic and/or structural differences, the "appearance" of the filter belies what really happens when you fill it w/ hot circulating oil. For example, EVERY one of these "scrapbook analyses" makes the lowly orange Fram out to be horrid. Yeah, it's definitely at the "cheap" end WRT to how it's built, but if it WERE as bad as one might believe from hanging out in car forums, we'd have dead cars strewn so thick we couldn't drive thru, around or over them! Fram only sells about a kazillion and a half of them every year between their Fram brand and all the house brands they make--how many actual documented failures do we actually see? And while I don't use them anymore, I have run them up to nearly 200k miles on other cars before my Subie came along, w/ zero defects or complaints. And, to tell the truth, the only reason I bothered looking for something else was that my Subie's the ONLY car I've ever owned that's persnickety about its oil filters!

There ARE tests to determine how well the filter actually does its job, but even they can result in skewed results if one says it's X% efficient and the next one's only 0.95X%--are they testing the same thing? Look up "beta ratio" for some info on how some of these tests are done. My tiny bit of research indicates the industry's been pretty much on its own for setting standards and advertising test results, though some people have been working to come up w/ some universal standards so we're always comparing apples to apples, not sometimes oranges, bananas and grapes.

But the pix ARE nice...

Rick

Not only nice, they provide valuable information.

From an engineering point of view the Fram filters may be adequate for their application but from the consumer/market economics point of view the consumer ought to know whether he wants to pay USD 5.00 for quality A or essentially the same amount of money for quality B. They seem to speak a thousand words to me.

M.J.