1976 MGB, Mobil 1 15W50, 1385 miles

[craigq]

Code:

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Vehicle History

Dad's toy. The engine was rebuilt [hot-tank, cylinders bored, new pistons/rings etc.]

at 97358 miles.



OCI

This oil was in use since 14-May-2006.



Sample Date 4-Sept-2007

Analysis Date 7-Sept-2007

Lab WearCheck Canada





***Vehicle ID***

Make MG

Model B

Year 1976

Engine 18V672Z 1.8L L4

Miles on Engine 8561

Miles on Vehicle 105919





***Oil Identification***

Oil Brand Mobil

Oil Series Mobil 1 SuperSyn

Oil SAE J300 15W50

API SX SL

Miles on Oil 1385

Months In Service 15.6





***Elements***

Antimony Sb NR

Cadmium Cd NR

Vanadium V 0.1

Aluminum Al 3.8

Chromium Cr 3.8

Iron Fe 20

Copper Cu 5.2

Lead Pb 60

Tin Sn 0.8

Molybdenum Mo 76

Nickel 0.0

Manganese Mn 17

Silver Ag 0.4

Titanium Ti 0.1

Potassium K 0.8

Boron B 138

Silicon Si 6.7

Sodium Na 6.9

Calcium Ca 2770

Magnesium Mg 40

Phosporus P 1128

Zinc Zn 1313

Barium Ba 0.2

Sulfur 2427







***Viscosity***

cST @ 100 C 15.2

SUS @ 210 F NR





***Misc***

Flashpoint (F) NR

Fuel %
Antifreeze % NR

Water %
Insolubles % NR

Sulfation 60

Oxidation 73

Nitration 50

ZDDP NR

TBN NR

TAN NR

Ferrous Debris NR

Fuel Soot % NR

Glycol
ISO Code NR

Additives None

URL NR

Notes Lab reports wear rates are normal, and to resample at the next service interval to monitor.

Location Ottawa, ON, CAN





***Filters used***

Air Filter UNI Pancake Filters

Oil Filter Motomaster Formula 1 F1-43

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[Geoff]

That's a lot of lead. My guesses:

- leaded fuel residues
- weak oil pump (or spring behind the pressure relief valve)
- crank not true or not polished - it is '70s
- bearing clearances wrong after rebuild
- high tension clutch pressing hard against thrust bearing
- particle streak through a bearing shell
- it's just normal

I'd actually try a lower viscosity like 10w-40 or 10w-30, particularly if you don't break 30 C. No doubt the original spec for the motor was 20w-50.

 

[Geoff]

On second look, since the tin and antimony (from bearing babbitt) are low I would go back to lead residues.

 

[craigq]

If my memory serves me right, Peter Burgess recommended frequent main bearing replacements as preventative maintenance in the 1800cc B-series engine (something along the order of every 50K miles, I have to re-read "How To Power Tune MGB 4 Cylinder Engines to double-check, but I don't have it here). With the lead readings from this engine I think I am beginning to see why. It *might* just be normal

The crank was re-ground/polished, bearing clearances were mic'd and plastigauged and the crank was verified to spin freely after each cap was tightened. Thrust bearings were a little odd, but I can't remember why (the rebuild was a while ago). New oil pump, verified to spin freely too before install (the first one we had purchased was binding so we returned it and purchased a second one).

This engine always runs hot (it regularly sees ambient temps above 30*C), it hasn't overheated yet, but MGB's are not known for cool running. This one doesn't have an oil cooler fitted...