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And as long as we old farts are gathered around the digital campfire exchanging old oil stories, there's this to keep in mind, too.
The 'high' and 'low' marks on the dipstick were, of course, calibrated for the stock VW engine — with no extended sump. When you bolt on an extended sump, the 'low' mark is no longer nearly as low as it used to be. When it says 'low', you now still have lots of oil in your extended sump. You could probably run the car with the oil at 'low' all the time without mucking anything up.
But, don't do that. Just keep in mind what those marks are now telling you.
I also have an extended sump, external filter, external cooler, and all the external oil lines that connect it all together. All of that holds about 4.5 quarts.
So five quarts should more than do you. Pour in about 3.5 quarts, fire it up and idle a bit to fill up the filter, cooler, connecting lines and such. Shut it down and check the dipstick. That should tell you how much more to add. It's still about a quart twixt low and high.
And, as noted above, you'll probably want to run it a skosh below the 'high' mark to keep the crank from frothing things up. It's plenty OK to do that now, since you've got so much more oil than any original engine did.
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