Coloradoguy

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.

Spring44

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.

V2Rocket

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...

Coloradoguy

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.)

Turbodan

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

Coloradoguy

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.

V2Rocket

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.

william_b_noble

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.

Want to be

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.

V2Rocket

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

FHMotorsport

I would go with Millers Oils 10W50

Coloradoguy

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

FHMotorsport

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

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

Coloradoguy

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.

jeffro951

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.