Oil weight spec thinning over time?

[MontePrix28]

The title may be a little misleading.

I have an older vehicle from the 1970s, so I am looking to run an oil that is high in zinc.

Regarding my question, is 20W50 from the 1970s the same thickness as 20W50 made in 2020? I feel like I remember reading a thread where the specs (thickness) to be an Xw-30 or Xw-40, etc, weight has changed over time.

The vehicle's applicable oil chart ranges anywhere from 10W-30 to 20W-50 as recommended oils. I personally have just run a conventional 10W-40, but I'm looking for something that is more "designed" for older vehicles or had what old oils had in them. I'm not a thinnie regarding oil, but I'm also not a thickie, so that's why I usually ran 10W-40. I put low miles on the vehicle so if it's causing extra wear I wouldn't really notice. I've been looking at the VALVOLINE VR1 oil, comes in 10/30 or 20/50. The engine is an old subaru boxer EA71.

Any input to what oil would be best for this engine?

Thank you in advance.

 

[ka9mnx]

I'm not familiar with that engine but it has been surviving well on modern oils for the last 20+ years. Modern oils are multiple times better than the oils you are wanting. I have engines that were spec'd for ancient oil and I'm happier using modern stuff. I don't think that engine needs more ZN than modern oils provide. My flat tappet 1965 designed F-150 runs quite well on modern oil at 260k miles. Any 10w-30 would be my choice.

 

[OilUzer]

Quote
I remember reading a thread where the specs (thickness) to be an Xw-30 or Xw-40, etc, weight has changed over time. ...


Good question. Isn't that part of SAE spec and did it change over time?
I am sure @kschachn knows the answer.

 

[viscous]

I don't think that engine needs more ZN than modern oils provide.

Classic Car oil

www.widman.biz

 

[circuitsmith]

I'm looking for something that is more "designed" for older vehicles or had what old oils had in them.

Perhaps a 15w-40 diesel oil?

 

[SkulltulaHouse]

While not available in 10w40, if you're thinking of 20w50, also consider Kendall GT-1 Competition Motor Oil with LiquiTek, conventional. Has Phosphorus, wt % 0.109; Zinc, wt % 0.120

GT-1® COMPETITION MOTOR OIL WITH LIQUITEK® - Kendall Motor Oil

Kendall® GT-1 Competition Motor Oil with LiquiTek protection additive is a high-quality, conventional automotive engine oil designed for use in gasoline-fueled passenger cars and light trucks that do not require an ILSAC GF-6 oil for warranty coverage. The SAE 20W-50 and SAE 50 viscosity grades...

kendallmotoroil.com

A bit less ZDDP than Valvoline VR1, but the Kendall is API SP rated

Would likely need to order online and have it shipped, unless you can pick up at a local distributor.


A case (12 qts) is $51.85 on kendallmotoroils.com (with an S) with shipping included in the price, which is run by Petroleum Service Company (PSC). The Petroleum Service Company's own website (not the specifically Kendall branded site) has shipping as a separate charge: 12 qts is $42.50 plus shipping, depending on whee you live, shipping may be cheaper going through PSC's site, if for you specific address shipping is less than about ~$9 (for my address, ground shipping on the PSC site is $12, so for me it would be better to order on kendallmotoroils). However, the PSC site gives us a price without shipping which we can use to approximate a local pick up price at a distributor of about $3.54 per qt. VR1 is about $8 at most auto part stores (maybe $6 per qt if you can find someone who sells the 5 qt jug), but I think is $5 at Menards if you have one near by

 

[mpack88]

I'm running that oil in my 84 chrysler. Runs great with it. Smokes a little less. Lol

 

[AutoMechanic]

I use the 20W-50 high zinc racing oil from Vavloline in my 1973 Beetle and it runs on it just fine back when stuff like this was new I am told they just put whatever was available at the time from a barrel during the 70s and back.