Mobil 1 15-50 and piston slap

[cookie]

I have been toying with the idea of switching my 113,400 mile Forester to synthetic for some time. Since I have new seals that was not an issue for me.

I recently switched my BMW from BMW semi synthetic to Mobil 1 and was pleased with the results.

I decided to try the heaviest weight Mobil 1 I could get since my Subie has high miles and it's not very cold in the SF area. I have only had three starts since the switch so no long term results, I'll keep you guys posted especially if I blow it up.

Either I've gone deaf or I have lost my piston slap. I was just down in the garage starting the car needlessly to hear it again. I can always hear it slap clearly in the garage here.

I have no idea if this is going to work long term, it seems too easy. If it was this easy why wouldn't Subaru do it?

I also have no idea if this will work for folks in colder climates.

[quailman]

I tried Mobil 1 in one of my high mileage Subies and that stuff leaked out of everywhere that had a gasket or seal,

 

I have been toying with the idea of switching my 113,400 mile Forester to synthetic for some time. Since I have new seals that was not an issue for me.

I recently switched my BMW from BMW semi synthetic to Mobil 1 and was pleased with the results.

I decided to try the heaviest weight Mobil 1 I could get since my Subie has high miles and it's not very cold in the SF area. I have only had three starts since the switch so no long term results, I'll keep you guys posted especially if I blow it up.

Either I've gone deaf or I have lost my piston slap. I was just down in the garage starting the car needlessly to hear it again. I can always hear it slap clearly in the garage here.

I have no idea if this is going to work long term, it seems too easy. If it was this easy why wouldn't Subaru do it?

I also have no idea if this will work for folks in colder climates.

[mattocs]

I might run some synthetic oil when I get my seals done in the next few months. I hope for it to quite down the clicking and ticking the engine makes (it isn't a loud ticking...but I don't like it.) Keep us posted on how it goes with the thicker oil.

[krissy00]

I own a 98 legacy gt and I run synthetic oil in it (Ams Oil) it runs great I never tried mobil 1 with the Ams oil you can run the oil for 25,000 miles and change the oil filter every 12,000 and so far so good I ran it in my old xt6 also and no problems.....

[mattocs]

I think I would change oil and filter every 6,000 - 8,000 miles.

[Scoobaroo]

15W50 will perhaps cling to the piston skirts a bit better when you shut the engine off and it cools down. Thus, there may be a wee bit more oil on the skirts and cylinder walls at the next cold start.

 

15W50 is not an option during Wyoming winters, though.

 

15W50 is 100% (or more) thicker than 5w30 or 10W30. Your engine's oil pump has to work overtime to pump that thick "goop" through your engine.

 

Oil is a coolant, also. Thicker 50 weight oils are much more resistant to flow than thinner ones. The less quarts that flow through your engine per minute, the less potential it has to remove heat from bearings, camshafts, etc.

Your fuel mileage will drop a bit, too.

 

Use what works best for you, but i'll stick with 5W30. My engine is quietest on Wally World "SuperTech" 5W30 than any other kind of oil. Paying $4.68 for 5 quarts and $2.00 for a "SuperTech" oil filter does my heart good, too.

[Scottbaru]

Synthetic oil is supposed to be better at cushioning, might help with slap. I've switched my last seven cars to Mobil 1, most have gone over 200k without a problem. I've run M1 15W50 in my Audi and Toyotas for many years, and it gets a little cold here. I just put M1 5W30 in my Legacy, will switch to 15W50 if I get any clatter or ticking.

[tracer46]

I've just swapped my 2.5 engine in my 98 Outback for a 2.2 with 72,000 miles. I'm looking at going to a semi-synthetic oil but wanted to get some feedback and see what others think. I've used semi and synthetic before with good results but haven't used it for a few years. Anyone have any problems with either of these oils in the 2.2 engine. Thanks in advance for suggestions.

[cookie]

On a very cold start I can hear a bit of slap that goes away quickly. I agree that the thicker oil is probably sticking on the pistons better. I also agree that it may affect my mileage and I will be measureing that over the next few fill ups. So far no leaks.

It is hard to really measure piston slap by ear, but my guess is about a 90% reduction. On second starts I had easily heard slap whenever cold. This is gone completely.

This also may not be an option for very cold climates as the oil is much thicker, which is what prompted me to try it.

[hklaine]

I've just swapped my 2.5 engine in my 98 Outback for a 2.2 with 72,000 miles. I'm looking at going to a semi-synthetic oil but wanted to get some feedback and see what others think. I've used semi and synthetic before with good results but haven't used it for a few years. Anyone have any problems with either of these oils in the 2.2 engine. Thanks in advance for suggestions.

 

From what I have heard, the semi-synths only have to include some small amount of synthetic oil (10% ?) by regulations. I heard from an engineer at Mobil that if you want a real synthetic mix, combine 1 qt of synth with 3 qts of dino.

 

I can't personally verify this. I use the dino all the way and change it with the OEM filter at 3k.

[cookie]

That was what was in my BMW from new. It must have worked fairly well because I got a nice chatty note from the Blackstone lab guy on my last oil test saying "your M roadster is looking good."

I do think that the dino oil will work fairly well, the semi synth is OK, and the full synth is just a bit better.

One of the questions I had for the synthetic oils were if they would justify the extra cost. Quieting my piston slap will go a long way toward this in my Subaru. The other thing I am concerned about is that my Forester always uses a bit of oil. When I go on a long high speed trip useage goes up, otherwise it is about a quart of dino 10-30 to an oil change. One concern I have is how much synthetic oil will it use between changes? At over 100,000 miles I have an engine with some wear on it, and usually a worn engine does a bit better with a thicker oil in a moderate to warm climate.

On the BMW I just did not want to go to the dealer all the time for my oil. I can get Mobil 1 pretty easily and I can just keep mobil 1 on hand now. It would not hurt either car if I top up with either weight. On my BMW no difference in operation or mileage was discernable with the change from semi to full synthetic.

[danz75]

I have an 03 OBW and I recently switched from regular oil to Mobil 1 5W-30. I was under the impression that the piston slap would either go away or that it will be a lot less.

 

Well, after about 4 weeks, I still don't think it is any less and if anything, I think it seems to have a 'brighter' sound.

Since I had the car new, I'm starting to wonder if the piston slap thing is getting worse. It's usually worse when it's cold but I've also noticed that it usually only goes away about 5-8 minutes after the car has warmed up. I had the dealer check that out but was told that it's SOA policy that as long as it goes away, it's within specs and so SOA will not do anything.

 

Back to syn, I'm not sure if I've noticed any difference in performance but as long as it will prolong the life of my engine, I'm willing to use it.

 

my $0.02

[friendly_jacek]

Many people observed worse noise in subaru with mobil 1 5W30 or 10W30.

You may want to try mobil 1 5W40.

[WJM]

I run Motul (The same stuff that the SUBARU World Rally Team uses in its rally car) 5w30 fully synthetic in my RX, EA82 turbo engine, its got 182k miles on it...no leaks. Its had the Motul in it for 20k miles now.

[mattocs]

I might go with a semi-synthetic oil. If that quites my engine down a bit, I'll stick with it. If not, i'll give Mobile 1 a try. I always have ran Castrol GTX in my car.

[Tiny Clark]

I was looking at the open engine picture displayed on the subaru.com last week.

 

I don't understand what the bad significance of longer piston skirts would be. With an alloy material, the total mass can't be that much of a diff, and the friction would seem to be negligable. Of course, I'm not dining on raw fish and wine made out of rice...

 

Maybe they should have taken the material saved on the pistons and used it for a different cup holder.

[mattocs]

 

Maybe they should have taken the material saved on the pistons and used it for a different cup holder.

 

 

Ditto. I hate the things...flimsy chunks of poop.

[cookie]

on the 2.5 pistons. But diesels slap for years with no damage. I still think there must be slightly less wear if the slap is less.

I am not sure if my noise is reduced because of the oil staying put better, or if it is just thicker. last night the temp was low 40s which is cold for here. I had slap until the oil pressure came up that was quite noticeable, about 15 seconds. It then quieted down until you could hardly hear it.Before I would have had slap until the engine temp gauge came up to halfway.

This makes me think an interesting experiment would be to put straight 30 weight dino in a 2.5 with piston slap and see what happens. Since I just paid big bucks for the Mobil 1 I won't be trying this anytime soon.

Since several of you have tried the lighter synthetics with no noticeable difference in slap this makes me wonder what the difference is. The Mobil 1 in my BMW seems lighter for the given weight than dino.

On to the mileage test which starts today. No perceptable difference in cranking speed for the starter, but it is not that cold here.

[Scottbaru]

But diesels slap for years with no damage.

I thought that sound was detonation on the compression stroke?

 

These engines are pretty wide, they're probably doing everything possible to shorten those cylinders and the block so you don't have to change the spark plugs through the wheel well. Short skirts would be a logical part of that if you wanted to up the displacement without widening the engine.

[cookie]

but the sound you hear is when the piston skirt slaps into the cylinder wall. This is the same thing these short skirt pistons are doing in 2.5 Subarus. The slap is the piston skirt hitting the wall. I have couple of hundered miles on the experiment now and will probably fill up tomorrow as I will put another 50 miles on it tonight.

I look forward to seeing if gas mileage changes one way or the other, or stays the same.

[Gnuman]

I thought that sound was detonation on the compression stroke?

 

These engines are pretty wide, they're probably doing everything possible to shorten those cylinders and the block so you don't have to change the spark plugs through the wheel well. Short skirts would be a logical part of that if you wanted to up the displacement without widening the engine.

 

OK, just how does that fit together? If you want to up the displacement without widening the engine, you make larger bores, without touching the stroke. That much I understand, but how does that require the skirts to be shorter? Or am I missing something here?

[blitz]

These engines are pretty wide, they're probably doing everything possible to shorten those cylinders and the block so you don't have to change the spark plugs through the wheel well. Short skirts would be a logical part of that if you wanted to up the displacement without widening the engine.

I actually did (what I thought was ) a brilliant diatribe on this a while back.

 

To wit (summary):

 

The biggest problem with the boxer configuration stuffed into a passenger car is the overall width. To keep it in check, Subaru works toward the bottom-end of the acceptable bore/stroke ratio AND the bottom-end of the acceptable rod/stroke ratio.

 

My analysis was that THIS was the major culprit in the Subaru fuel-thirstyness phenomemon. I also opined that this dimensional uniqueness allowed Subaru's to benefit from slightly thicker (not necessarily thick) oil ...reason being: lower piston speed and higher piston side-loads.

[Gnuman]

Interesting. How far back? a link perhaps? You can PM or email it to me if you don't think anyone else would be interested. . .

[cookie]

I guess I have always thought Subaru shortened the skirt to reduce friction,there is room for the counter measure piston which I have been told has a slightly longer skirt. I have never seen one myself, so if anyone has please chime in here.I have seen pistons in the past that had extended skirts notched for the rod to prevent slap. Teflon buttons are also possible.

I have never heard of a Porsche owner complaining of piston slap, so it seems possible to make a non slapping boxer.

[blitz]

a link perhaps?

http://www.ultimatesubaru.org/forum/showthread.php?t=20239

 

Long thread ...700-something posts.

 

Obviously the AWD is a factor, but I started comparing other AWD vehicles of similar weight and displacement and found that Subaru was still behind.

 

I figured it had something to do with the unique engine ...did a rabid search on my day off and comfirmed my suspicions.