Okay, so living in Denmark and listening to that little man with a hammer banging on my engine after a frosty morning cold start, I have been researching and testing a range of different oils. A few days ago, I tried yet another new oil, and this time I may have cracked it!

 

Mobil Delvac 1 5W-40

 

NOW, before the arguments begin, here's a list of the other oils I have tried:

 

Mobil 1 5W-50

Mobil 1 5W-40

Mobil 1 5W-30

Mobil 1 0W-40

 

Castrol GTX 10W-40

Castrol Magnatec 5W-40

 

Redline 10W-40

 

Shell Ultra 5W-40

 

 

So, a Diesel engine oil works best! Delvac 1 is API-SL approved so it's perfectly safe in petrol engines. However, compared to almost every other 5W-40 oil, it has the highest viscosity at low temps. Yet it thins out nicely to comply the engine tolerances at operating temperature. This last point is a "worry" when using Mobil 1 5W-50 oil, because the oil could be considered too thick to circulate fast enough, and also strain the oil pump unnecessarily.

 

Most 5W-xx oils have a viscosity of 75-80 centistokes at 40C, but Delvac 1 comes in at 102cst.

 

 

So henceforth, Delvac 1 5W-40 is my recommendation for the best oil to quell that nasty piston slap.

 

Sound is muted, far less metallic, and goes away quickly.

Cool, maybe i'll try it.

 

I did my own version of your experiment with 50/50 mix of 10w-30 and 5w-40. It was an improvement.

 

I've heard others have good results with diesel grade oil.

Hmmm, that's interesting.

 

What sort of temperatures do you experience there?

 

How does the price of the Delvac compare with regular Mobil1 oil?

Sube's fit fleet-oils ("diesel awl") like a glove ...couldn't tell you why tho.

 

If I lived in a warmer climate, I would't hesitate to use regular ol' 15W-40 dino fleet-lube year round.

 

**** ******!

You don't have Castrol High Mileage there?

You don't have Castrol High Mileage there?

 

Castrol 5w30 high mileage CAUSED tappet sticking in my EJ22. Never had it before until I tried the stuff. After running it for a week it seemed to stop, but I changed my oil for 5w30 synth instead (Canadian Tire, supposedly made by shell). After switching I had nary a sticking tappet again.

Castrol 5w30 high mileage CAUSED tappet sticking in my EJ22. Never had it before until I tried the stuff. After running it for a week it seemed to stop, but I changed my oil for 5w30 synth instead (Canadian Tire, supposedly made by shell). After switching I had nary a sticking tappet again.

 

edit - I know this was for piston slap, but I would think the thicker oil at start-up may be more detrimental for piston slap.

I'm running Amsoil 5W-30 in my 97 Legacy the noise seems less and goes away quickly on cold New England mornings. Amsoil also has a longer drain interval of 5k miles which is important for me since I average about 1100 miles per week.

 

I ran the Amsoil 10W-30 and the noise was a bit louder at first but still went away within 5 minutes.

 

Mal

Sure we have the Castrol High Mileage stuff over here.

 

Mobil Delvac 1 is the same price level as gasoline specific Mobil 1.

 

 

The thinner oils I tried - 0W-40, 5W-30 - did NOT help to silence piston slap.

Thicker is better, but it's gotta be something that will cling to the piston surface even when warm, to avoid full run off during the nightly cool down. That way the piston will have a thin layer of high viscosity oil on it in the morning.

 

Temperatures reaching about -5 C during the nights at present, average for winter. Thats about 22F..isn't it?

I used the T&SUV 5w-40 and had excellent results last summer, but it's been discontinued. I should be changing the oil soon and I'll be using Rotella T Synthetic 5w-40, I expect that the results should be similar.

 

(my daughters insist )

On bobisthoilguy some folks have reported less slap with Havoline dino oil. I'm still running the Mobil1 15-50 and my slap is still reduced, but this is a fairly heavy oil and I don't think it would be suitable for low temps. Keep us in the loop on how that works out!

I used rotella 5W40 for several years in my 2000 and never developed the piston slap. However, don't know % of people with the problem as not everyone will have piston slap I guess. Rotella synthetic is a very good oil. Group 3 but much cheaper than delvac. Similar heavy duty additive pack. Has the 40C viscosity a bit lower than delvac, in the 90 range.

 

This year I will try Castrol syntec made in Germany 0W30 (aka castrol SLX), the only XW30 oil I know that has ACEA:A3 rating (HTHS>3.7). I will see if this will help with MPG vs rotella.

 

It sounds like to cushion the piston slap, oil has to coat the cylinders. Light oil will not stay on the cylinder wall overnight, heavy oil will. I guess the esthers in Castrol magnatec/start-up oils coating the cylinder is just a marketing stuff.

 

Another question is if one uses thick oil in low temp to decrease the sound of piston slap, would there be a penalty with increased wear in valvetrain and bearings?

German Castrol 0w-30 is my winter oil of choice, and it performs repectably for a 30 weight regarding piston slap. I have yet to hear anything quieter than a 10w or 15w-40, in our EJ25 at least.

It seems spring is finally starting to chime in, and this morning the temp was up to +5 degrees C - about 40 F.

 

And guess what? There was ZERO piston slap. I kept slowing down, starting off in first gear again, revving through 1800-2500rpm where it used to be worst, there was nothing !!!

 

Perhaps the Delvac has had time to wash away the remaining Shell Ultra, or perhaps the warm weather helped, but I never thought the slap could dissappear again.

 

The only "but" here is that my engine is a 2.0 liter, so the results might not be quite as pronounced on the 2.5's y'all have over there

Warmer weather helps the 2.5s too. My slap is nil on a warm summer morning.

I think the slap and the head gaskets that leak in the cold were developed to punish Canadians for not buying enough Subarus. It just caught some of the rest of us as collateral damage.

I used rotella 5W40 for several years in my 2000 and never developed the piston slap. However, don't know % of people with the problem as not everyone will have piston slap I guess. Rotella synthetic is a very good oil. Group 3 but much cheaper than delvac. Similar heavy duty additive pack. Has the 40C viscosity a bit lower than delvac, in the 90 range.

 

This year I will try Castrol syntec made in Germany 0W30 (aka castrol SLX), the only XW30 oil I know that has ACEA:A3 rating (HTHS>3.7). I will see if this will help with MPG vs rotella.

 

It sounds like to cushion the piston slap, oil has to coat the cylinders. Light oil will not stay on the cylinder wall overnight, heavy oil will. I guess the esthers in Castrol magnatec/start-up oils coating the cylinder is just a marketing stuff.

 

Another question is if one uses thick oil in low temp to decrease the sound of piston slap, would there be a penalty with increased wear in valvetrain and bearings?

In the old days my dad would run straight 20w in the winter and 30w in the summer. If there is concern about the higher viscosty RANGE being TOO thick in the winter, i see no reason a lower range couldn't be used. For some of you guys 0-30w may be best for a coupla, 3 months (even IF a little piston slap returns) then in spring move up to a 10-x or 15-x range of oil.

 

I am gonna try running Rotella synthetic 5-40 year round in my WRX and may switch the outback over to it. I just feel the flow from 5w is never really required here but the Rotella is not expensive and has the protection of a 40w. If I they make it (and someone stocks it at a good price) I would run it in 10-40.

 

ymmv

 

Carl

I live in south central PA and our Subie garage puts in 15W40 year-round; keeps the engine cleaner and helps control the piston slap according to the mechanics.

 

Brian M.

In my most humble opinion 15W-xx is too thick for ambient temperatures below 10-15 degrees Centrigrade.

 

(What's that in "your money", about 50 F ? )

To keep using a heavier weight oil and to minimize piston slap during warm-up during winter months the best thing to do is add an engine block heater for those cold nights. I lived in Fairbanks for 5 years and those winters were harsh.

 

Did you know that: For air temperatures of -20 to -35 F, the air is so dense that it is like having a tubo on your engine. For temperatures below -40 F, it is dumb to drive your car - all the rubber parts lose their flexibility and shocks and suspension parts wear out quickly. When you drive in the morning after a car has sat overnight during a Fairbanks winter night, the tires go thump, thump, thump until they warm up enough to allow the rubber to flex. I would never buy a used car out of Fairbanks.

 

PS: Referring to non-synthetic oil as Dino oil is bad. Our earth oil deposits are the result of millions of years of deposits of dead micro-organism life in the oceans.

PS: Referring to non-synthetic oil as Dino oil is bad. Our earth oil deposits are the result of millions of years of deposits of dead micro-organism life in the oceans.

You mean, it's politically incorrect. That makes me want to call it that, even though I question the certainty of petroleum being a "fossil" fuel.

The "quietest" oil I've found is the house brand 10W-40 at Advance Auto Parts. I tried it before I got my oil leak fixed, because Mobil 1 is too expensive in an engine that leaks 1 quart per week. I was very surprised at how quiet the piston slap was at startup, and how quickly it disappeared as the engine warmed. It slowed the leak considerably, also.

 

One strange thing - a bright yellow goop formed at the oil filler neck. I don't like brightly colored goop in my engines, so I haven't used the stuff since.

 

I don't know what the shop put in when they fixed my head gaskets and oil leaks, but it's slapping pretty loud. I'll try the Delvac 1 next oil change (coming up in 300 miles).

 

-Ron '99 OBW

PS: Referring to non-synthetic oil as Dino oil is bad. Our earth oil deposits are the result of millions of years of deposits of dead micro-organism life in the oceans.

 

Are we offending the dinos or the germs?

 

Personally, I'd be interested in trying whale oil.

 

BTW, before the flame war starts, it was a joke. Can you imagine what it would smell like when it hit the exhaust manifold?

Are we offending the dinos or the germs?

 

Personally, I'd be interested in trying whale oil.

 

BTW, before the flame war starts, it was a joke. Can you imagine what it would smell like when it hit the exhaust manifold?

 

Everyone's heard of Dexron II right? Well, the original Dexron (I?) had whale oil in it!

 

Also, it was the increasing scarcity/cost of whale oil that caused the development and popularity of kerosene - starting our move to the use of petroleum products!

 

just a little trivia

 

Carl

One strange thing - a bright yellow goop formed at the oil filler neck. I don't like brightly colored goop in my engines, so I haven't used the stuff since.

 

I noticed that in my subaru once. It was a long time ago, the car was serviced by a shop and had no idea what brand of oil was used.

Hey all . I want to try the delvac or rotella in my 02 outback to see if I can quiet the slap.

The only problem is that it I can only find it in the 15w40 weight.

I tried Pep Boys and Advanced auto

Any suggestions on other stores to buy it in .

 

Thanks In advanced

 

Mike K