Oil pressure gauge

[Roxylass]

What pressure should be showing on my oil gauge 

when engine starts the needle shows 40

After 20/30minutes it drops to 20

engine seems fine not heating up 

engine in question sr2 air cooled 

[Tony Brooks]

I would suggest probably OK, but check the oil. Those engines are known for internal fuel leaks that dilute the oil, causing low oil pressure. Feel the oil on the dipstick between thumb and finger and compare it with new oil. also smell it for an unburned diesel small. If this is the problem and it is ignored, the engine will eventually seize up or run away on oil/diesel fumes.

[Roxylass]

Thanks for the quick reply tony 

engine oil looking like new only changed last year 9and a half pints

no blackness to it at all or diesel smell 

[Tony Brooks]

1 hour ago, Roxylass said:

Thanks for the quick reply tony 

engine oil looking like new only changed last year 9and a half pints

no blackness to it at all or diesel smell 

 

Make sure the oil is the correct SAE specification. My guess is that originally, for UK summer use it would be SAE 30 and SAE 20 for winter, then multigrades came along so probably SAE 20W50 but nowadays, we have things like SAE 5W20 which are probably totally unsuitable because A. it is probably synthetic oil, but as long as the engine is well run in probably won't do much harm in the short term, but more importantly B. it is too runny, so low oil pressure. Hopefully a Lister expert will be along to give chapter and verse.

[bizzard]

The SR2 generally run at about 15-20  psi when up to normal running temp. Tick over around 6-10 psi.

Edited May 7, 2023 by bizzard

[Steve56]

Here's the relevant info from the Lister Manual

[Roxylass]

Many thanks for the reply’s lads

Saved me buying a new gauge 

Cheers