worf928

A crush washer is a one-use item. But, yes, you are more-correct than you know: my dealer's oil-change "tech" didn't bother with the crush washer so that makes the o-ring infinitely more-reusable than a crush washer.

And so too for me. From now on. I've had to do remedial oil-pan work on far too many 928s. I'm not about to let that happen on the 991 or 981.

I need to smack myself in the head. Repeatedly. I had this fantasy that I wouldn't have to get serious about DIY on the 9*1s for about 10 years. I need a PWIS...

dflowerz

Great write-up. Thank you!

911Forever

Years ago when I did my own oil change, I would let the oil completely drain out. Then I would put in another quart of oil and let it drain out too to wash out any additional gunk.

Is it advisable to do it to our 991.1 or 991.2 engines? (This is based upon forum info that not all motor oil are drained out during oil service.)

LexVan

Unnecessary. Seems like a great way to waste $10.

Drain the oil hot. Change it every 5,000 miles. Yearly if you do low mileage.

911Forever

Thanks, Lex.

Valvefloat991

Keep in mind that the 9A2 engines in the 991.2 actually hold almost 14 quarts (13 liters) of oil, of which only 8.5 or so (8 liters) drains due to the complex "internal dry sump" design.

As a result, even after three oil changes (three years or 30,000 miles according to the factory recommended schedule), there's still nearly a quart of the engine's original oil left in the sump. So 911Forever is not on the wrong track here.

I wonder if any of those trapped 5 liters could be removed using some sort of suction tube introduced through the oil filling tube.

LexVan

Where's this data from? Probably not much different than the 91A motors, or the old Mezger engines in the 993s. This concern over old residual oil is a non issue, especially if you read/study UOAs.

Jenner

I disagree.

Pouring in a quart to let it "wash out gunk" is nothing but a waste. You can't run the engine to circulate it. It just passes through and doesn't do anything useful.

Most of missing 5 liters is contained in the lines running from the engine to the front bumper (and back again) as well as the two oil coolers that sit up there and the lines between them.

There is no way to drain the oil from that without removing the front bumper, disconnecting the lines and draining that way. No one is going to do that and using a suction tube into the engine or sump isn't going going to pull out any of that oil. The semi practical way to remove more of the old oil would be to drain, refill, then run the engine to circulate/mix the new and old oil and then drain it again and even then you are only getting a mixture of what was in the front oil coolers...not worth the time or effort or cost.

Best just to change and replace what drains out. Porsche suggests every 15,000 km and most of us are already changing the oil once a year or every 5000km because we are all mental and crazy about our 911s! It's overkill and just a waste of time, $ and oil.

LexVan

If you're worried about "gunk" in the oil, add a magnetic drain plug to your regiment. Here's mine after 5,000 miles.

Jenner

Is that even an option for the 991.2 with plastic plug and pan? (considering the topic of this thread we are only talking bout the .2)

LexVan

Ooops you're right. See, we should have had a seperate 991.1 Forum and a seperate 991.2 Forum.

Valvefloat991

LexVan, the data comes straight from the press kit. I suspect that the 991.1 engine is similar. But the Metzger engines used a proper dry sump with a separate tank. The only residual oil in that engine was in the oil lines and coolers.

Jenner, I'm not aware that there are any oil coolers in the front of a 991. There are only coolant radiators up front and the oil is cooled using an oil/water heat exchanger located in the engine compartment. The undrained oil is stuck somewhere in the "internal dry sump" and that's why I suggested the suction approach. I haven't tried it and it might not work, but if it did, it would be relatively easy and wouldn't involve any extra oil.

By the way, the Porsche oil change recommendation is 10,000 miles or one year, whichever comes first.

Since we all change our oil hot in order to drain as much of it as possible, it's slightly shocking that nearly 40 percent of the oil does not drain by design.

Jenner

Ah right I was thinking of my older 911s that had an oil cooler up front. Any idea the capacity of the oil radiator used for the oil/water heat exchange? That and it's lines still have to keep some oil in the system that can't be drained no?

My fault on the interval I should have written km not miles, as in Porsche suggests changing the oil ever 15,000 km. So we are saying the same thing. Either way most on Rennlist change way more often than is necessary and obsess way too much about oil, brand, weight, changing etc.

Valvefloat991

I don't know where the oil/water heat exchanger is on the 991, but on most engines, it's sandwiched between the oil filter housing and the block, so there's little or nothing in the way of plumbing to trap oil.

And I agree that many people obsess about oil. However, most engines only trap less than a quart of oil during an oil change--not 5 quarts. That's what got my attention. Certainly we only want to put excellent oil in these engines, given that some of that oil will be in there for a very long time.

P.S. I did do an initial oil change at 1100 miles and now that my car is at 5800 miles, perhaps it's time for another one. Then I'll only have 2 quarts of the original oil circulating in the engine. If I do this, I'll try some suction to see if I can extract any more oil.

bkrantz

Would this help?