Mobil 1 15-50 and piston slap

[Setright]

Well, I just switched from M1 0W-40 to my summer M1 5W-50 and the slap is louder, but still goes away. Temps are just over freezing in the morning this time of year.

 

Piston skirts: Yes, extending the skirt would cause collision with the crankshaft counter weights. In a boxer, these counter weights are small, but still there. Most pistons have been "notched" or shaped around the weights for the last 20- odd years.

Not sure why Subaru insists on such short skirts, maybe it's a sixties revival thing ;-)

[Scoobaroo]

Shortened piston skirts are only part of the problem. In newer engines, the wrist pins and piston ring packs are located higher on the pistons in an effort to reduce emissions by eliminating unburned gasses that used to hide between the piston crown and the top piston ring. Higher wrist pins and piston rings = less stability of the piston skirt in the bore. Inadequate cooling in #4(?) cylinder may contribute to slight piston skirt collapse (Smaller diameter piston not due to wear).

 

This is all becoming very complicated because of government mandated emission requirements and fuel economy standards.

"Building them like they used to" is not an option anymore. Reducing internal friction and rotating mass is the only way that car makers can meet emissions standards. Something has to give.

 

Changing weights / types of oil really won't help much. Cookie lives in San Francisco with a very constant, moderate climate. 15w-50 could actually cause engine damage elsewhere in below zero temps. Subaru oil pumps are designed to pump 5w-30 or 10w-30 at a certain rate and volume. Using heavy weight oils could cause an oil filter to remain in bypass mode too long resulting in unfiltered oil.

It's probably best to stick with 5w-30 and tolerate a few moments of slapping.

[cookie]

mileage. Today I got the best mileage I have seen. 25.77 mpg. This is just one tankfull and over a holiday weekend so it may not be representitive. This is about 1 MPG better than I saw before the oil change.This is not what I expected which would have been a slight decrease, but one tank means nothing.

I certainly agree that oil this heavy may not be the ticket in a cold climate, but it seems to be working OK here. I also expect my slapping could easily be much worse in a colder climate.

[blitz]

Cookie, I haven't seen any evidence that the slap can be eliminated through oil selection (despite an overwhelming intuition that suggests otherwise ). At best the slap can be mitigated somewhat. Myself, I've just accepted it as part of the 2.5's characteristics.

 

Mobil 1 15W-50 is great oil for any starting temp over 40*f, run the heck out of it.

 

17.4 cst @ 100*C isn't thick oil. 20+cst is thick by my definition.

[cookie]

Blitz,

 

I did not really think the slap would disapear, but years ago when I used to re-ring engines and hone the heck out of them they usually slapped. A heavier oil would quiet it somewhat, but not eliminate it. That seems to be exactly what I have here.

This is a bit of an unexpected side effect as I did not expect as much change as I got. It does make me wish I had bit the bullet and tried this a couple of years ago, but all the stories about bad experiences with leaking seals put me off.

At this point I wonder if this would work as well for other folks in mild climates or if this oil just works well in the particular engine in my car.

I was talking to our head of training today and he is running Dello Diesel oil in his gas van. This is working well for him as he added it when the car was not very old. It sure does keep his engine clean with those high detergents.

I usually run exactly what the manufacturer reccomends for no surprises. In this case it is yet to be seen how it affects mileage long term, if the slap stays quieter or gets worse,how much oil it burns, and if it affects valve gear.

My fingers are currently crossed.

[friendly_jacek]

I will be changing from 10W30 dino to 5W40 Rotella oil in a few weeks. I will make measurements before and after with a sound level meter. I will try making recordings, too, just for fun.

I plan to run 15W40 Delo next summer. It is the best engine oil you can get for under $2/qt, it is not just diesel oil, it has API SL certification.

[Setright]

Scoobaroo: Mobil 1 5W-50 will easily flow at low temperatures and won't stress the oil pump or filter by-pass valve.

 

I do agree that 15W-50 might cause problems at low temperatures.

[cookie]

It will be interesting to see what effect diesel spec oil has, and I agree that is great oil. As a former fleet mechanic I have poured in many a gallon of diesel oil. I like the idea of measureing the sound before and after as it will give a much better comparison than my rolling the windows down when I start the car.

I probably look pretty silly out there in the morning with my windows down, everything noisy off, and watching the second hand of my watch.

[bratman2]

I know oil has changed alot in the past twenty years but not many years ago Mobile1 15w50 would out flow any 10w30 conventional oil. Cookie, if it works why change it, even though Rotella and Delo are great oils. When I first switched my little Brat to Mobile1, back when it had 142k, I used 15w50, saw several 20 degree mornings with no start up issues at all (the only reason for the 15w50 was unfounded fear of leaks) now 0 degrees probably would be different. I would stick to what works myself. Currently on 10w30 at 194k with no leaks or problems, also run 5w30 in the wife's 2003 Legacy, all Mobile1 and the great thing is no piston slap in her car. Her Legacy does a 35 mile country commute through one small town each way to work and has broken the 30mpg mark this past year regularly (she has the 5 spd). Strange that some have piston slap and others don't. For semisynthetic there is no regulations that I know of, they can drop in 5% hydrocracked dino oil in the US and call it semisynthetic. If anyone wants to go this route I would definatily make my own and 3 to 1 is a good ratio that will beat any off the shelf blend imho.

[cookie]

Thanks for the input Bratman. I am glad to hear from somebody who has tried 15-50. I agree whith you that this stuff really flows well. Timeing the tap this morning was 10 seconds. It was mild and rainy, as soon as it splashs some oil around the tap is gone. It seems to stay on the pistons all day, but after 10 hours at night it leaks off, (at least this is what I think is happening). It does seem like 10-15 seconds of slap has got to be better for the motor than 3 minutes or so.

I wonder if running the stuff from new would have prevented it in the first place? You are right and I am going to stick with this stuff unless I get some bad effects down the road.

I think my engine is fairly clean as it has had fresh dino every 3,000 miles from new. I might change out the Mobil 1 at 3,000 this first time to be sure, or sooner if it gets dark and starts to look ugly.

[bratman2]

When I bought my daughter a 93 Legacy w/114k I switched it to Mobile1 10w30 at 115k. Drained at 5k with the same concerns that you had about possible cleaning out old crud. With the second change I installed a new filter at 125k and changed at 130k. Ran 10k changes on this Legacy until we sold it with 177k miles for the measily sum of $650 due to her tagging a black bear on the driver's side. My coworker who bought the car and wasn't concerned too much over the apppearance of the drivers side fender and both doors has 184k on it as of saturday. He continues on with the Mobile1. Can't help but wonder why a bear has to bounce all down the side of a vehicle. My daughter stated "I know you probably don't believe me but it really happened", of course the thick black hair in the door trim confirmed her story. Bear made it past the Legacy but unfornatily not the next car behind her.

[cookie]

Ok, I guess I sould take a couple of things from this.

1 Mobil 1 is proably going to work OK.

2 Don't mess with bears.

Thanks again for sharing your experience.

[kudd]

Ok...so the 154k 2.2 (I still don't know the EAxx designations...) that I just bought had 5-50 Mobil 1 in it in Portland OR for the past 5 years. Would there be any harm done to switch back to 10-30 or 10-40 dino goo? Or is that a bad no-no and I need to stick with the M1? And..I don't even know if M1 is full synth or semi. After the 4725 mile trip home I'm due for a change...except of course w/the M1 in it can s'posedly go longer.Also, it did run low so I put a half quart of Penzoil in. Was all they had where I was and I figured that any oil was better than none.:-\

[cookie]

My understanding is that Mobil 1 is fully synthetic. Any oil is better than no oil. I have not heard of problems from mixing as some folks mix up thier own anyway.

If you can I would stick with the synthetic. If not dino will probably run just fine. I have run nearly all my cars on dino for over 40 years. You can switch with no ill effects.

The only real reason to use Mobil 1 is to prevent a tiny bit of wear and perhaps improve your fuel mileage a tiny bit. I am not sure the extended change interval is going to make up for the extra expense of the oil at this point.

[Scoobaroo]

1 Mobil 1 is proably going to work OK.

.

 

I agree. Especially in San Fran's climate. The coldest temps you'll encounter are probably low 50's; fine for 15w50 in an engine with some miles on it.

 

Our '02 likes Wally World 5w-30 Dino. Probably has an extra dose of moly or something. Minor slapping for a few moments when cold started. I really don't stress about the slap. It's minor, really. I'm interested in it from an engineering standpoint.

 

My '87 Toyota pickup had piston slap that would make you run for cover on a cold morning. I accept piston slap as part of owning a Japaneese enginered car. Almost all of them have one pesky engine noise or another. Noises are rarely fatal with Japaneese engines.

 

Keep us updated, Cookie, huh??

[danz75]

This applies somewhat to this question.

 

I have had the opportunity to drive 2 different 04 OBW 2.5 in the last month. One had a ticking sound on cold start but went away after about a minute. The other, the ticking was so faint that you couldn't tell unless you listened carefully.

 

My 03 OBW on the other hand....lets' you know very well and clearly that it ticks...and it does it for awhile longer even after the engine has warmed up.

 

Were there any changes in the engines of the 04 models?

[cookie]

When I got my 99 Forester it had a tiny tick on start up. As the mileage wore on the slap stayed longer and longer. Then it started on the second starting of the day and stayed until the car reaced normal operating temperature. By this time it was over 100,000 miles, stabilized and did not seem to get worse unless it was very cold.

I think by now Subaru must be fitting upgraded pistons. I would also love to hear more about this from someone who knows.

[Scoobaroo]

 

Were there any changes in the engines of the 04 models?

 

 

Not likely. Did the '04's that you listened to have less mileage on them than your '03?

 

Due to the design of the 2.5, it already has about the longest piston skirts that it is able to have.

As for fitting them to closer tolerances, you can only fit a brand new piston in a brand new bore so tightly before you risk piston seizure as the cold piston expands. The majority of 2.5's will have cold piston noise as the miles rack up. (Unless one lives in Miami.)

 

The 2.5 is kind of a flawed design; too much displacement in too small of a crankcase. Head gasket sealing is compromised greatly. Bore and stroke dimensions are past practical limits. They make good horsepower, but the same amount of HP could have been gotten from the 2.2 design with careful fuel management and more aggressive valve/cam profiles.

 

I'd still rather have a "flawed design" 2.5 than a "well designed" Chevy.

[Gnuman]

Ok...so the 154k 2.2 (I still don't know the EAxx designations...) that I just bought had 5-50 Mobil 1 in it in Portland OR for the past 5 years. Would there be any harm done to switch back to 10-30 or 10-40 dino goo? Or is that a bad no-no and I need to stick with the M1? And..I don't even know if M1 is full synth or semi. After the 4725 mile trip home I'm due for a change...except of course w/the M1 in it can s'posedly go longer.Also, it did run low so I put a half quart of Penzoil in. Was all they had where I was and I figured that any oil was better than none.:-\

 

Kudd, all of the cars listed in your signature are EJ22 engines. EA was old gen stuff (FWIU). I cannot see harm in going back to dino oil on that car, or even changing the viscosity to match your climate.

[danz75]

Not likely. Did the '04's that you listened to have less mileage on them than your '03?

 

Actually, the mileage on the 04 OBW (dealer loaner vehicles too!!!) was higher than my 03 OBW. I did talk to the service rep and they checked out my car for me after I complained that the ticking seems to be louder and longer than the loaner vehicles and was told that as long as the ticking goes away after the engine warms up to operating temp, SOA will not do anything. So in my case, it usually still ticks about 5 mins or more after it has warmed up but it does go away....whereas the 2 04 OBW that I've driven.....don't seem to suffer from the 'tick of death'.

 

The service rep also said that every car was different and some will tick and some won't. I wonder why is there such a wide range in quality?

[kudd]

Kudd, all of the cars listed in your signature are EJ22 engines. EA was old gen stuff (FWIU). I cannot see harm in going back to dino oil on that car, or even changing the viscosity to match your climate.

 

Thanks Gnuman, rotted bones it'll be!

[subie94]

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.

 

 

how much that stuff cost yah??? and were'd yah get it?

been thinking about trying royal purple

[cookie]

The second tank of gas gave me 24.6 MPG. This tank was a lot of start and stop and short trip. last night I was caught in a traffic jam. This seems to be only a couple of tenths better than with dino oil.

[Setright]

Just read in a local car magazine that Honda's hot VTEC engines also have cold engine piston slap. Article says not to worry.

 

Still, I don't get: My 1990 EJ22 NEVER slapped, even with over 180k miles on it.

[99obw]

I just thought I would chime in here and back up cookie on his claims. I too have found the boxer to prefer something thicker than the average 30 weight with regard to piston slap and engine noise in general. I won't try a 50 weight yet, but if the bearings start to tire I may. I also think, based on tracking mileage carefully while using different viscosity oils, that the effect that oil viscosity has on fuel economy is vastly overblown by auto manufacturers. The colder the climate and the shorter the trips the greater the difference will be between thin and thick oils. Viscosity index of the oil also plays a significant role. I am very suspicious of the push for 20 weight oils by Ford, GM, and Honda. I think these oils benefit the manufacturers (CAFE, Corporate Average Fuel Economy) more than the consumer.