Wewe @rant.
Here is the reality illustrated in an example - I own an opel astra 1.8 ecotec. I use kawaida fuel that u r trying to trash. The service interval from manufacturer with current mileage is 9,000KM. when new - 12,000KM. But I know we have a problem in the country,so do the serice sooner inspite of using high grade oils etc. Actually the biggest problem I see here is not fuel,but our dusty environment. Most pple even now are driving 'severely starved engines' - starved of air,by choked air filers. That is the biggest issue as far as I am concerned. When I blow air into the filter and the air box,I usually see a huge difference in both consumption and acceleration. I service sooner to avoid regrets,but still use highest possible grade of oil - it's stil cheap anyway - not synthetic though.
I know we dont have high octane fuels,super-low sulphur diesel etc,but we can still make do with what we have without much of a problem. a fleet of about 60 landcruisers and many nissan minibuses from a famous company in town are still running despite 300,000 plus kms on the diesel engines....usiogope mafuta sana,but always 'kunywa' at a proper station where quality is not in doubt.
Bidii yangu