San Rensho

2000 2.7, 115k. I've had this car for a few weeks now and it has a slight rattle, for less than a second, when started cold. It sounds like lifter noise to me. When I inspected the car prepurchase, I made sure to start it up with the engine dead cold, and I don't remember hearing anything.

As soon as I got the car home, the first thing I did was change the oil to Mobil 1 15-50, car had M1 0-40 in it when I bought it.

So my question is, will the thicker oil make the car more likely to rattle on a cold startup and should I switch back to 0-40?

insite

i personally wouldn't sweat it. viscous collapse of the oil due to heat is the bigger issue with these engines IMO. the thicker oil is the better way to go. 15-50 might be a bit thick for just street duty. you may want to consider a 5W-40 or 10W-40 unless you live somewhere really hot.

Plyman438

LN Engineering on its website recommends higher viscosity oil such as 5 or 10W 40 oil for those Porsche's with potential IMS problems. 5W seems like good compromise to me. Not too thin or too thick.

Macster

Maybe.

In your car's case the old oil could have been due to be changed. I have noticed an engine after an oil change is quieter upon startup because fresh oil is almost aways more viscous than the oil that was in the engine, the oil in the engine having been diluted from water and gasoline contamination and becoming less viscous, thinner because of it.

In changing the oil from 0w-40 to 15w-50 the biggest factor in reducing the startup noise may have just been replacing old diluted oil with fresh oil.

Had you stayed with 0w-40 oil the engine might have exhibited the same reduction in noise upon startup.

The noise you heard comes from some lifter clatter and camchain dragging that occurs when an engine sits a while and the lifters bleed down and the tensioners bleed down and allow the chains to go slack.

Some noise is normal. The longer the engine sits unused... the noisier it will likely be upon restart.

One 'trick' to make an engine quiet is to before someone looks at it to start the engine and let it run a moment. This pumps up the lifters and the camchain tensioners. Shut off the engine and after a few minutes unless one is very very observant one can't tell the engine was started recently.

Yet, upon startup the lifters are quiet as is the camchain because the lifters/tensioners are still pumped up from the previous start and have not yet had time to bleed down, unless they're in very poor shape.

Should you switch back to 0w-40? Don't know. Up to you. If you don't want to stay with 15w-50 and you don't want to switch to 0w-40, you could consider using a 5w-40 oil. Lots of approved oils to choose from. Or you could use a 5w-50 oil. Mobil 1 5w-50 is an approved oil.

Whatever oil you run don't run it too long. I change my engines' oil every 5K miles. A bit of overkill maybe, but it takes some worry out of losing an engine prematurely due to running oil too long.

Sincerely,

Macster.