Long oil service intervals are JOKE! Manufacturers recommend engine oil, keep oil specification according to manufacturer (such as VW 505.01 for VW 2.0 TDi PD engine) and choose optimal oil for your driving style.
Almost every oil has lower viscosity than manufacturers claim. Even premium oil such as Liqui Moly Diesel High Tech 5W-40 has got something like 5W-35. And it degrades to 5W-30 levels after 7,000km.
Oil lab report from my old Skoda Fabia HR II.
Cheap garage oils last about 5000km
Oil lab report from my “new” Hilda HR I.
I’ve recently received a report from my new car – results were shocking. It’s a car from Germany with full service history. Oil had just 10k km, and it was, simply put, killing the engine. Few such oil services and engine is dead!
Premium oils last about 10,000km.
Soot is a problem number one for diesel engine oils – despite oil still has additives and keeps viscosity, it’s full of soot at about 10k km!
VAG cars are especially sensitive to clean oils – unless you wish to kill your turbo.
You never know with oils – marketing is based on lies. I suggest you to invest in oil analysis – it’s cheaper than car engine replacement!
Oil is cheap – engine NOT. Filters are cheap – car NOT.