It's not even remotely the same engine, but the Carledo's Vauxhall unit is very sensitive to both time and oil grade. I run it on the recommended 10/40 semi synthetic but once put 5/30 in by mistake, within a week, I was experiencing considerable pressure loss, especially when hot. Changing back to the proper stuff fixed that, but the car also does circa 2000 miles per year, yet at close to it's annual oil change time, there is a warning drop of about 0.5bar from it's normal max of 4.5bar and idle drops from 3bar to 1bar. When I drop the oil out, it's almost as clean as the new oil going in and looks and feels fine, but it's obviously "lost it's edge" cos when I put the new oil and filter in everything returns to normal -until the next year! It's been like that for 5 years now without changing, but this year I have been using the car more and I am getting the early warning signs now rather than in March as is usual. I probably should use a better oil, that would last longer, maybe a full synthetic, but I expect I will just stay with the cheap stuff and change it a bit more frequently.
Before you start messing with what works, try an oil change first, it might just be enough to last till you have more time to deal with it!
2 door '73 Toledo with Vauxhall Carlton 2.0 8v engine OWF 797M (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine EGP 247T (The Dolomega)
'91 Cavalier 2ltr 8v auto
'95 Cavalier 2ltr 16v auto
Spectrum Auto Services, Servicing, Repairs, MOT prep. Apprentice served Triumph Specialist for 45 years and home of Maverick Triumph.PM for more info or quotes.