Oil Question
 

I know that questions of oil can spark flame wars like nothing else, but I'd just like some advice here.

Going through the records that came with my car, I see that the oil was changed at the following intervals:

122,423 miles GTX 10w-30
125,551 miles 5w-30 "Super Motor Oil" (I have no idea what this is, but at $2.50 a quart, I seriously doubt that it was synthetic.)
127,422 miles No type of oil specified on receipt
131,133 miles Mobil 1 0w-40 Synthetic

My car had just under 148,000 miles when I took possession of it and can find no other receipts for oil changes. I plan on changing the oil but my question is should I stick with the 0w-40 or go back to something like 10w-30 dino oil? I've read that using the Porsche-recommended 0w-40 could lead to oil leaks (I haven't noticed any) in a high-mileage car like mine. My car seems to start OK and the pressure hangs around the 3.5 bar level when warmed up. All opinions/comments welcomed and appreciated.

I live in Aurora, Colorado, and my car lives in a garage. Thanks.

I am an original owner of an '84 944 and when these cars were new, most of the Porsche dealer shops used Castrol 20w-50 oil. In the late 1980's I switched to an independent porsche specialist shop to do my work and they switched me over to Valvoline 20w-50R Racing Oil.

I still use the Valvoline VR oil and the car now has 150k miles on it and it still runs great, doesn't smoke or use oil, and has 4-5 Bars of oil pressure at normal driving speeds. The reason that they liked the 20w-50 ValvolineVR at the shop is that it had more Zinc additives than other oils.

depends on the climate you drive the car in.
Colorado winter driver? 0-40 or 10-40 will probably suffice.
"warm weather" (aka 33 degrees and higher) 20W50...

What would you say to 5 quarts 20w-50 with one quart of Marvel Mystery Oil year round? Still too thick for winter driving? (I've always been a big fan of MMO, but have no experience with it in Porsches.)

for the older porsche cars I like Brad Penn oil with high zinc content.

Thanks. I admit I had to look that brand up; I'd never heard of Brad Penn. I want something they stock at my local O'Reilly's so my choices may be somewhat limited.

WOULDN'T bother mix/match. if it's snowing, 0- or 10-w40 is fine.

also, you can get the same oil for cheaper from Walmart, FYI. like $12/5 qts rather than $22 or whatever Oreilly charges.

I put over 250K miles on my 85.5, bought new, using "generic" 10/40 oil, changed every 3K miles. car was running fine when topgear USA bought it from me and destroyed it -(season 2, episode 2 I think). if you change at 3K miles you can use cheap oil and the engine stays happy. the car isn't hard on oil so you don't need the fancy stuff.

You have a flat tappet engine and it requires ZDDP, aka - zinc.

Either you buy oil with zinc or use an additive.

Porsche has ZDDP oil forsale.

Amazon and Evilbay have multiple brands forsale. Buy a case of oil and a good Mahle or porsche filter.

Brad Penn, Kendal and other brands but find the one with zinc. You will not be able to buy it at Walmart, but I have found some Napa stores having an oil with high ZDDP .

Is my oil weight choices.

10/40 - winter
20/50 - Summer

I've always thought Zero weight oil is for modern cars. Goal to save gas not the car.

castrol gtx high mileage 20W50 has sufficient zddp levels (~1200ppm or so).
get a 5-qt jug at walmart for $12.

I would go with Millers Oils 10W50

Ended up going with 0W40 Mobil 1. That's what the PO had in there so I thought I'd keep it going.

I would read this post too before I go with lightweight oils.

https://rennlist.com/forums/924-931-...t-reading.html

Food for thought.

I don't have a twin cam model and I don't race or push it hard.

On the other hand, I'm not really out driving that much in brutal winter conditions so I'm thinking of switching to 20w-50 just to be on the safe side. Thanks for the input.

I use the 0-40 mobile as well, the one that says for European cars because it has zinc in it, it is available at all auto part stores.