SAE 30 vs. 20W-50 for a short OCI

[Snagglefoot]

Originally Posted By: Garak
Originally Posted By: Silk
I wouldn't call an A3/B4 20W-50 weak in any way...but may not be on the shelf in the US.

Nope, not too likely. I know I haven't seen one here, either.


Yep. Just the watered down stuff.

 

[BrocLuno]

Look, you want something along the lines of a robust 40 in the heat. The cold flow grade does not matter as it'll never see winter. Just use a 15W-40 HDEO like Delo or Delvac. Cheap enough and robust as the come. No need for synthetic, it'll be out of there in a few months.

 

[fdcg27]

Any current 10W-40 PCMO has sufficiently high HTHS to work well in any old Brit/Euro engine for which the original recommended grade was 20W-50. That's also a pretty big spread, so I question how long the oil actually remains a 50 in actual use after a little permanent shearing.
Back in the day I used 10W-40 PCMO in my MGB since I considered 20W-50 thicker than required for a robust old engine design that really didn't make much power and that made only noise beyond 5K revs, although redline was 6K IIRC. You could win drag races with most then current early emissions era sedans, though, which was more a tribute to the short gearing and easy fast shifting than the available power.
A 15W-40 HDEO would offer more ZDDP if that matters and would be a very solid oil in use.

 

[bunnspecial]

For those wondering, here is a factory oil chart. As said, it's not a shared sump like a Mini(this is a front engine, rear wheel drive vehicle and has a separate engine and gearbox). If you read, however, the oil suggested here is for the engine, transmission and carburetors(the dashpot that SUs have in place of an accelerator pump). I don't know what the "oil can" it refers to is, and I'm guessing "distributor" means the lubricant for the mechanical advance mechanism. The overdrive, if present, shares a sump with the main gearbox-it uses a wet "cone clutch" to engage/disengage. FWIW, I changed the transmission in the car about two years ago(my old one had cracked 3rd and 4th gear synchros and the speedometer drive gear had seemingly disintegrated)-it's a standard 4-speed 4-sync box and has had the same fill of Supertech 20W-50 since it was installed.



Thanks for the suggestions-I'll see what I can find on sale and will either use Delo 40 or Delo 15W-40.

 

[FCD]

As Shannow said before 1959 BMC A-Series engines all were spec'd for simply SAE 30, then 20W-50 became the "universal" oil for them, shared sump or not.
So SAE 30 or 40 would be fine for a couple months.
I wuld probably run something like Shell Rotella T4/T5 15W-40 or Valvoline Vr1 20W-50 for the long term in it

, A- Series engines tend to leak oil no matter what and they purr really happy on a good HDEO or 20W-50 PCMO.

 

[bunnspecial]

Originally Posted By: FordCapriDriver
As Shannow said before 1959 BMC A-Series engines all were spec'd for simply SAE 30, then 20W-50 became the "universal" oil for them, shared sump or not.
So SAE 30 or 40 would be fine for a couple months.
I wuld probably run something like Shell Rotella T4/T5 15W-40 or Valvoline Vr1 20W-50 for the long term in it

, A- Series engines tend to leak oil no matter what and they purr really happy on a good HDEO or 20W-50 PCMO.


B engine, not A...although they're more alike than different. The A just looks like a 3/4 scale model of a B

(and a 1275 A engine doesn't have removable tappet galley covers, which eliminates on common source of oil leaks but also means a full tear-down if you want to change tappets or even inadvertently lfit one...)

With that said, the rear oil seal on the B engine is a different design from that on the A. B engine only leak there if the seal is bad, while A engine basically can't be stopped from leaking.

My main oil loss now is through the PCV system, which tells me that the rings are shot. At one point, I made a catch can out of a 1L side arm flask packed with glass wool. In an hour on the interstate, I'd collect ~100ml of oil.

BTW, I have a big stash of VR-1 20W-50, but I don't want to dip into it for this OCI. This is basically out of necessity of "I need to change the oil after the head gasket job but want to save the good oil for when the engine is actually healthy again."

 

[FCD]

Originally Posted By: bunnspecial
Originally Posted By: FordCapriDriver
As Shannow said before 1959 BMC A-Series engines all were spec'd for simply SAE 30, then 20W-50 became the "universal" oil for them, shared sump or not.
So SAE 30 or 40 would be fine for a couple months.
I wuld probably run something like Shell Rotella T4/T5 15W-40 or Valvoline Vr1 20W-50 for the long term in it

, A- Series engines tend to leak oil no matter what and they purr really happy on a good HDEO or 20W-50 PCMO.


B engine, not A...although they're more alike than different. The A just looks like a 3/4 scale model of a B

(and a 1275 A engine doesn't have removable tappet galley covers, which eliminates on common source of oil leaks but also means a full tear-down if you want to change tappets or even inadvertently lfit one...)

With that said, the rear oil seal on the B engine is a different design from that on the A. B engine only leak there if the seal is bad, while A engine basically can't be stopped from leaking.

My main oil loss now is through the PCV system, which tells me that the rings are shot. At one point, I made a catch can out of a 1L side arm flask packed with glass wool. In an hour on the interstate, I'd collect ~100ml of oil.

BTW, I have a big stash of VR-1 20W-50, but I don't want to dip into it for this OCI. This is basically out of necessity of "I need to change the oil after the head gasket job but want to save the good oil for when the engine is actually healthy again."

Aha, understood.

 

[Shannow]

Yeah, my comments are why 20W50 came into existence, then dominated the UK/Australian markets, not that this engine and box are combined...the grade existed because of the FWD british cars.


For e.g. in Oz, the recommendation for the Holden V-8s (including the Chev engine Holdens) in the late '60s was 10W30-SAE30...but was 20W50 from the early 1970s all the way into the late 1990s (My Caprice with L67 was specced for 20W50, with 15W40 in the "cold"...heaviest it ever got was 15W40, and mostly 30 A3/B4s)