Engine oil for original 1973 2.4 L

[fmarinelli]

Would appreciate recommendations for engine oil viscosity and maker.
Here's some info:
1973.5 911T
2.4 liter with CIS
Original engine with 100,000 miles; only one top-end rebuild in 1988
Change oil once per year
Colorado: typical summer highs about 90 F; typical winter lows about 15 F
Drive about 2000 miles per year
Oil consumption about 1 quart every 700 miles, but drips a drop or two per day from main bearing.
Is zinc additive a good idea for this engine?
What do you think about Swepco 306, which is reasonably priced.
Have been using Castrol GTX, with 50/50 mix of 10W-40 and 20W-50.
Takes about 11 quarts per oil change, so cost is an issue.
Thanks!

[LakeCleElum]

20-50 Brad Penn or Valvoline VR 20-50. No synethic Zinc is very important.
I have a 73.5 and had the same mag case engine for many years with the same usage until I went with a high compression 3.2.

Your engine can have oil pressure issues when/if the temp gets too warm. If you see oil temps in the 230 area, your oil pressure get will drop into the danger zone. If that happens, bet back to us for advice about cleaning the engine mounted cooler and maybe adding an exterior cooler that the later cars came from the factory with. Before trying to save a few bucks on cheap oil and no cooler, go price a full rebuild on a mag case engine. $18,000 is the current price range.
Your 1st post, welcome. Now, pictures are required of the great 73.5 model you have.

G'luck...

[javadog]

Swepco is fine for that car. Would not use Castrol at all.


JR

[bkreigsr]

What were trying to accomplish by mixing weights?
I've been under the impression that any mixture will revert back to the oil with the lower viscosity, maybe old wives tale, maybe not.
Brad Penn should be fine for your application. 20-50 if most of your driving is 'spirited' - 15-40 if you are driving 'normally'.
Bill K

[gamin]

Have used Valvoline VR-1 Racing 20-50 in both my old air cooled for quite some time. It is readily available at auto parts stores and in fact is on sale locally at O'Reilly's through the end of October. And zinc (zddp) is very necessary in our old engines. VR-1 Racing has it. Stock up when it is on sale.

[Sunroof]

I have owned my 1973.5T for over 17 years now (2.4L, CIS, coupe) and have been using Valvoline 20-50 Racing since the day I bought it. No issues. Very dependable. The 2.4 is not noted to run hot; however, you can add a few inexpensive items to get about a needles worth of lower temps (the HEAT SHEETS and the famous COOLER COLLAR). Check them out. Here is a photo of my 73.5T.

Bob

[Nick Triesch]

Porsche Classic 20/50 synthetic blend motor oil. This is the oil that Porsche recommends for early air cooled cars.

[HarryD]

I use Brad Penn 20W-50 in my 2.4L CIS. It is currently under repair and the internals look great.

[boxster03]

Shell 30WT - good enough for Porsche in 1973

[wayne robson]

Sunroof ,you have a real great looking 911.thanks for the photo.

[HarryD]

Originally Posted by boxster03

Shell 30WT - good enough for Porsche in 1973

Really? really?

You do know that the 30W oil in 1973 was totally different than whet you get now and multi-viz oils in 1973 were not very good.

Stick with a good 20W-50 or 15W-40 with decent ZDDP and TBN numbers